Head first servlets and jsp part 002 by Santonov

Chapter 8. Script-free pages

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#AN THE INCLUDED *30 HAVE ITS OWN DYNAMIC CONTENT )N YOUR EXAMPLES THE (EADER JSP MIGHT AS WELL HAVE BEEN A STATIC (EADER HTML PAGE

)T S A *30 SO YES IT CAN BE DYNAMIC BUT YOU RE RIGHTÂ&#x2C6; IN OUR EXAMPLE WE COULD HAVE MADE THE HEADER A STATIC (4-, PAGE AND IT WOULD HAVE WORKED IN EXACTLY THE SAME WAY 4HERE ARE A FEW LIMITATIONS THOUGH AN INCLUDED PAGE #!../4 CHANGE THE RESPONSE STATUS CODE OR SET HEADERS WHICH MEANS IT CAN T CALL SAY ADD#OOKIES 9OU WON T GET AN ERROR IF THE INCLUDED *30 TRIES TO DO THINGS IT CAN TÂ&#x2C6;YOU JUST WON T GET WHAT YOU ASKED FOR

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Chapter 8. Script-free pages Head First Servlets and JSP By Bert Bates, Kathy Sierra, Bryan Basham ISBN: 0596005407 Publisher: O'Reilly Prepared for Stephen Goss, Safari ID: stephengoss@gmx.net Print Publication Date: 8/1/2004 User number: 747221 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited.

Chapter 8. Script-free pages

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=P WP ;PMÂ¼[ ZQOP\ 4HINK ABOUT WHAT WE DID 7E MADE A PAGE FOR THE HEADER h(EADER JSPv )T WAS A NICE *30 ALL ON ITS OWN COMPLETE WITH ITS OPENING AND CLOSING (4-, AND "/$9 TAGS 4HEN WE MADE THE h#ONTACT JSPv AND IT TOO HAD NICE OPENING AND CLOSING TAGS 7ELL DIDN T WE SAY THAT EVERYTHING IN THE INCLUDED l LE IS PASTED VIRTUALLY INTO THE PAGE WITH THE INCLUDE 4HAT MEANS EVERYTHING 4HE CODE BELOW FROM THE GENERATED SERVLET WILL ./4 WORK IN ALL BROWSERS )T WORKED IN OURS BECAUSE WE GOT LUCKY RXW ZULWH Â³ KWPO! ERG\!?UÂ´ RXW ZULWH Â³?U KWPO!?U ERG\!?U LPJ VUF ?Â´LPDJHV :HE 6HUYLFHV MSJ?Â´ ! EU!U HP! VWURQJ!:H NQRZ KRZ WR PDNH 62$3 VXFN OHVV VWURQJ! HP! EU!?U?U ERG\!?U KWPO!?UÂ´ Yikes!! RXW ZULWH Â³?U EU!?U?U?U HP!:H FDQ KHOS HP! EU! EU!?U?U&RQWDFW XV DW Â³ RXW ZULWH MDYD ODQJ 6WULQJ RUJ DSDFKH MDVSHU UXQWLPH 3DJH&RQWH[W,PSO SURSULHWDU\(YDOXDWH Â³ ^LQLW3DUDP PDLQ(PDLO`Â´ MDYD ODQJ 6WULQJ FODVV 3DJH&RQWH[W BMVS[BSDJHBFRQWH[W QXOO IDOVH

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Chapter 8. Script-free pages

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Notice we took out all the HTML and BODY tags from the included Ă&#x17E;les.

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Note: this idea of stripping out the opening and closing tags applies to BOTH include mechanismsĂ&#x2018; <jsp:include> and the include directive.

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Chapter 8. Script-free pages

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<jsp:include> you add (or recan have a BODY, so th that the incl place) request paramet at uded thing ca ers n use.

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To the included Ă&#x17E;le, the param set with <jsp:para is just like any OT m> using EL to get it.HER request parameter. Here weĂ&#x2022;re

Note: this idea of params doesnĂ&#x2022;t make any sense with the include directive (which is not dynamic), so it applies ONLY to the <jsp:include> standard action.

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Chapter 8. Script-free pages

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<PM $R[X"NWZ _IZL& [\IVLIZL IK\QWV 9OU #!. FORWARD FROM ONE *30 TO ANOTHER /R FROM ONE *30 TO A SERVLET /R FROM ONE *30 TO ANY OTHER RESOURCE IN YOUR WEB APP /F COURSE YOU DON T USUALLY WANT TO DO THIS IN PRODUCTION BECAUSE IF YOU RE USING -6# THE 6IEW IS SUPPOSED TO BE THE 6IEW !ND THE 6IEW HAS NO BUSINESS DOING CONTROL LOGIC )N OTHER WORDS IT SHOULDN T BE THE 6IEW S JOB TO lGURE OUT IF THE GUY IS LOGGED IN OR NOTÂ&#x2C6;SOMEONE ELSE SHOULD HAVE MADE THAT DECISION THE #ONTROLLER BEFORE DECIDING TO FORWARD TO THE 6IEW "UT LET S SUSPEND ALL THAT GOOD -6# JUDGEMENT FOR THE TIME BEING AND SEE HOW WE COULD DO IT IF WE WERE TO FORWARD FROM A *30 PAGE TO SOMETHING ELSE 7HY BOTHER IF YOU LL NEVER DO IT 7ELL YOU MIGHT ONE DAY STUMBLE ON A PROBLEM WHERE JSP FORWARD IS A USEFUL SOLUTION -ORE IMPORTANTLY LIKE A LOT OF WHAT S IN THE BOOK AND THE EXAM THE USE OF JSP FORWARD IS OUT THERE ,URKING IN GAZILLIONS OF *30S THAT YOU MIGHT ONE DAY lND YOURSELF MAINTAINING OR IDEALLY REFACTORING

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Chapter 8. Script-free pages

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Chapter 8. Script-free pages

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Chapter 8. Script-free pages

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Chapter 8. Script-free pages

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By the way... you probably wonĂ&#x2022;t be able to run this yet because you donĂ&#x2022;t have JSTL in your web app. WeĂ&#x2022;ll do that in the next chapter.

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Chapter 8. Script-free pages

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%( WKH &RQWDLQHU $16:(56 /RRN DW WKLV VWDQGDUG DFWLRQ

class, s a type but scnoope, Note: this haNO y if ec T sp and it does it uses Ă&#x2019;pageĂ&#x201C;. which means

MVS XVH%HDQ LG Â´SHUVRQÂ´ W\SH Â´IRR (PSOR\HHÂ´ ! MVS VHW3URSHUW\ QDPH Â´SHUVRQÂ´ SURSHUW\ Â´QDPHÂ´ YDOXH Â´)UHGÂ´ ! NEVER The body willtless to MVS XVH%HDQ ! run! ItĂ&#x2022;s poin side a <jsp: 1DPH LV MVS JHW3URSHUW\ QDPH Â´SHUVRQÂ´ SURSHUW\ Â´QDPHÂ´ ! put a body ing if you have this far, useBean > taand no class! If we made itvanĂ&#x201C;. Ă&#x2019;E t in only a type e tag body pr Ă&#x2022;ll we Remember, thLY if a new :KDW KDSSHQV LI WKH VHUYOHW FRGH ORRNV OLNH executes ON d, which can bean is createwhen only IRR 3HUVRQ S QHZ IRR (PSOR\HH S VHW1DPH Âł(YDQÂ´ never happen no class) is UHTXHVW VHW$WWULEXWH ÂłSHUVRQÂ´ S a type (but e tag. th declared in at request FAILS at request time! The Ă&#x2019;personĂ&#x201C; attribute is stored es only a scope, so the <jsp:useBean > tag wonĂ&#x2022;t work since it speciĂ&#x17E; type speciĂ&#x17E;ed, type. The Container KNOWS that if you have only aname and scope. abstract there MUST be an existing bean attribute of that

3HUVRQ

:KDW KDSSHQV LI WKH VHUYOHW FRGH ORRNV OLNH IRR 3HUVRQ S QHZ IRR 3HUVRQ S VHW1DPH Âł(YDQÂ´ UHTXHVW VHW$WWULEXWH ÂłSHUVRQÂ´ S

6WULQJ JHW1DPH

YRLG VHW1DPH 6WULQJ

Actually, this servlet fails to compile. We cheated a little, since on this question it isnĂ&#x2022;t Ă&#x2019;Be the ContainerĂ&#x201C;, itĂ&#x2022;s more like Ă&#x2019;Be the COMPILERĂ&#x201C;. foo.Person is now abstract, so we canĂ&#x2022;t insta ntiate the foo.Person. (PSOR\HH LQW JHW(PS,'

YRLG VHW(PS,' LQW

:KDW KDSSHQV LI WKH VHUYOHW FRGH ORRNV OLNH IRR (PSOR\HH S QHZ IRR (PSOR\HH S VHW1DPH Âł(YDQÂ´ UHTXHVW VHW$WWULEXWH ÂłSHUVRQÂ´ S

Both classes are in the package Ă&#x2019;fooĂ&#x201C;.

This works Ă&#x17E;ne, and prints out Ă&#x2019;EvanĂ&#x201C;. Remember, the code INSIDE the body of <jsp:useBean> will NEVER run, since we speciĂ&#x17E;ed a type without class.

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Chapter 8. Script-free pages

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'IVEN AN (4-, FORM THAT USES CHECKBOXES TO ALLOW A USER TO SELECT MULTIPLE VALUES FOR A PARAMETER CALLED KREELHV 7HICH %, EXPRESSIONS EVALUATE TO THE lRST VALUE OF THE KREELHV PARAMETER #HOOSE ALL THAT APPLY

R ! ^SDUDP KREELHV` R " ^SDUDP9DOXH KREELHV` R # ^SDUDP9DOXHV KREELHV> @` R $ ^SDUDP9DOXHV KREELHV> @` R % ^SDUDP9DOXHV>KREELHV@> @` R & ^SDUDP9DOXHV>KREELHV@> @`

'IVEN THAT A WEB APPLICATION STORES THE WEBMASTER EMAIL ADDRESS IN THE SERVLET CONTEXT INITIALIZATION PARAMETER CALLED PDVWHU HPDLO 7HICH RETRIEVES THAT VALUE #HOOSE ALL THAT APPLY

R ! D KUHI Â¶PDLOWR ^LQLW3DUDP PDVWHU HPDLO`Â¶! HPDLO PH D!

R " D KUHI Â¶PDLOWR ^FRQWH[W3DUDP PDVWHU HPDLO`Â¶! HPDLO PH D!

R # D KUHI Â¶PDLOWR ^LQLW3DUDP>ÂµPDVWHU HPDLOÂ¶@`Â¶! HPDLO PH D!

R $ D KUHI Â¶PDLOWR ^FRQWH[W3DUDP>ÂµPDVWHU HPDLOÂ¶@`Â¶! HPDLO PH D!

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Chapter 8. Script-free pages

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'IVEN THE FOLLOWING *AVA CLASS SDFNDJH FRP P\FRPSDQ\ SXEOLF FODVV 0\)XQFWLRQV ^ SXEOLF VWDWLF 6WULQJ KHOOR 6WULQJ QDPH ^ UHWXUQ Â³+HOOR Â³ QDPH ` ` 4HIS CLASS REPRESENTS THE HANDLER FOR A FUNCTION THAT IS PART OF A TAG LIBRARY # WDJOLE XUL Â´KWWS P\FRPSDQ\ FRP WDJVÂ´ SUHÂ¿[ Â´FRPSÂ´ ! 7HICH 4AG ,IBRARY $ESCRIPTOR ENTRY DElNES THIS CUSTOM FUNCTION SO THAT IT CAN BE USED IN AN %, EXPRESSION

R ! WDJOLE! WDJ! QDPH!+HOOR QDPH! WDJ FODVV!FRP P\FRPSDQ\ 0\)XQFWLRQV WDJ FODVV! ERG\ FRQWHQW!-63 ERG\ FRQWHQW! WDJ! WDJOLE!

R " WDJOLE! IXQFWLRQ! QDPH!+HOOR QDPH! IXQFWLRQ FODVV!FRP P\FRPSDQ\ 0\)XQFWLRQV IXQFWLRQ FODVV! IXQFWLRQ VLJQDWXUH!MDYD ODQJ 6WULQJ KHOOR MDYD ODQJ 6WULQJ IXQFWLRQ VLJQDWXUH! IXQFWLRQ! WDJOLE!

R # ZHE DSS! VHUYOHW! VHUYOHW QDPH!KHOOR VHUYOHW QDPH! VHUYOHW FODVV!FRP P\FRPSDQ\ 0\)XQFWLRQV VHUYOHW FODVV! VHUYOHW! ZHE DSS!

R $ WDJOLE! IXQFWLRQ! QDPH!+HOOR QDPH! IXQFWLRQ FODVV!FRP P\FRPSDQ\ 0\)XQFWLRQV IXQFWLRQ FODVV! IXQFWLRQ VLJQDWXUH!KHOOR MDYD ODQJ 6WULQJ IXQFWLRQ VLJQDWXUH! IXQFWLRQ! WDJOLE!

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'IVEN SDFNDJH FRP H[DPSOH SXEOLF FODVV 7KH%HDQ ^ SULYDWH LQW YDOXH SXEOLF 7KH%HDQ ^ YDOXH ` SXEOLF LQW JHW9DOXH ^ UHWXUQ YDOXH ` SXEOLF YRLG VHW9DOXH LQW Y ^ YDOXH Y ` ` !SSUMING NO INSTANCES OF 7KH%HDQ HAVE BEEN CREATED YET WHICH *30 STANDARD ACTION STATEMENTS CREATE A NEW INSTANCE OF THIS BEAN AND STORE IT IN THE REQUEST SCOPE #HOOSE ALL THAT APPLY

R ! MVS XVH%HDQ QDPH Â´P\%HDQÂ´ W\SH Â´FRP H[DPSOH 7KH%HDQÂ´ !

R " MVS PDNH%HDQ QDPH Â´P\%HDQÂ´ W\SH Â´FRP H[DPSOH 7KH%HDQÂ´ !

R # MVS XVH%HDQ LG Â´P\%HDQÂ´ FODVV Â´FRP H[DPSOH 7KH%HDQÂ´ VFRSH Â´UHTXHVWÂ´ !

R $ MVS PDNH%HDQ LG Â´P\%HDQÂ´ FODVV Â´FRP H[DPSOH 7KH%HDQÂ´ VFRSH Â´UHTXHVWÂ´ !

'IVEN A -ODEL ARCHITECTURE IN WHICH A *30 PAGE HANDLES ALL OF THE CONTROLLER FUNCTIONS THAT *30 CONTROLLER NEEDS TO DISPATCH THE REQUEST TO ANOTHER *30 PAGE 7HICH STANDARD ACTION CODE WILL PERFORM THIS DISPATCH

R ! MVS IRUZDUG SDJH ÂÝLHZ MVSÂ´ ! R " MVS IRUZDUG Â¿OH ÂÝLHZ MVSÂ´ ! R # MVS GLVSDWFK SDJH ÂÝLHZ MVSÂ´ ! R $ MVS GLVSDWFK Â¿OH ÂÝLHZ MVSÂ´ !

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Chapter 8. Script-free pages

PRFN H[DPV

'IVEN MDYD XWLO /LVW OLVW QHZ MDYD XWLO $UUD\/LVW OLVW DGG Â³DÂ´ OLVW DGG Â³ Â´ OLVW DGG Â³FÂ´ UHTXHVW VHW$WWULEXWH Â³OLVWÂ´ OLVW UHTXHVW VHW$WWULEXWH Â³OLVW,G[Â´ Â³ Â´ ! LQVHUW FRGH KHUH ! 7HICH INSERTED AT LINE ARE VALID AND EVALUATE TO F #HOOSE ALL THAT APPLY

R ! ÔLVW ` R " ÔLVW> @` R # ÔLVW OLVW,G[ ` R $ ÔLVW>OLVW,G[ @` R % ÔLVW>ÂµOLVW,G[Â¶ @` R & ÔLVW>OLVW>ÂµOLVW,G[Â¶@@`

7HICH STATEMENTS ABOUT THE DOT AND >@ %, OPERATORS ARE TRUE #HOOSE ALL THAT APPLY

R ! ^IRR EDU` IS EQUIVALENT TO ^IRR>EDU@`

R " ÎRR EDU` IS EQUIVALENT TO ÎRR>Â³EDUÂ´@` R # ÎRR>Â³ Â´@` IS VALID SYNTAX IF IRR IS A 0DS R $ ^KHDGHU 8VHU $JHQW` IS EQUIVALENT TO ^KHDGHU>8VHU $JHQW@`

R % ^KHDGHU 8VHU $JHQW` IS EQUIVALENT TO ^KHDGHU>Â³8VHU $JHQWÂ´@`

R & ^IRR> @` IS VALID SYNTAX IF IRR IS A /LVW OR AN ARRAY

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Chapter 8. Script-free pages

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'IVEN A *30 PAGE WITH THE LINE ^ ` 7HAT WILL BE DISPLAYED

R ! R " R # R $ R % [ `

'IVEN ^SDUDP Â¿UVWQDPH` ^SDUDP PLGGOHQDPH` ^SDUDP ODVWQDPH` ^SDUDP9DOXHV ODVWQDPH> @` 7HICH DESCRIBES THE OUTPUT PRODUCED BY THIS PORTION OF A *30 PAGE WHEN PASSED THE QUERY STRING "Â¿UVWQDPH -RKQ ODVWQDPH 'RH

R ! -RKQ 'RH R " -RKQ 'RH 'RH R # -RKQ QXOO 'RH R $ -RKQ QXOO 'RH 'RH R % ! NULL POINTER EXCEPTION WILL BE THROWN

7HICH SHOW VALID USAGE OF %, IMPLICIT VARIABLES #HOOSE ALL THAT APPLY

R ! ^FRRNLHV IRR` R " ^LQLW3DUDP IRR` R # ^SDJH&RQWH[W IRR` R $ ^UHTXHVW6FRSH IRR` R % ^KHDGHU>Â³8VHU $JHQWÂ´@` R & ^UHTXHVW'LVSDWFKHU IRR` R ' ^SDJH&RQWH[W UHTXHVW UHTXHVW85,` \RX DUH KHUH

Chapter 8. Script-free pages

PRFN H[DPV

7HICH ARE TRUE ABOUT THE MVS XVH%HDQ! STANDARD ACTION #HOOSE ALL THAT APPLY

R ! 4HE LG ATTRIBUTE IS OPTIONAL R " 4HE VFRSH ATTRIBUTE IS REQUIRED R # 4HE VFRSH ATTRIBUTE IS OPTIONAL AND DEFAULTS TO UHTXHVW R $ %ITHER THE FODVV OR W\SH ATTRIBUTES MAY BE SPECIlED BUT AT LEAST ONE

R % )T IS VALID TO INCLUDE BOTH THE FODVV ATTRIBUTE AND THE W\SH ATTRIBUTE EVEN IF THEIR VALUES ARE ./4 THE SAME

(OW WOULD YOU INCLUDE DYNAMIC CONTENT IN A *30 SIMILAR TO A SERVER SIDE INCLUDE 33) #HOOSE ALL THAT APPLY

R ! # LQFOXGH Â¿OH Â´ VHJPHQWV IRRWHU MVSIÂ´ ! R " MVS IRUZDUG SDJH Â´ VHJPHQWV IRRWHU MVSIÂ´ ! R # MVS LQFOXGH SDJH Â´ VHJPHQWV IRRWHU MVSIÂ´ ! R $ 5HTXHVW'LVSDWFKHU GLVSDWFKHU UHTXHVW JHW5HTXHVW'LVSDWFKHU Â³ VHJPHQWV IRRWHU MVSIÂ´ GLVSDWFKHU LQFOXGH UHTXHVW UHVSRQVH

)N AN (4-, PAGE WITH A RICH GRAPHICAL LAYOUT WHICH *30 STANDARD ACTION CAN BE USED TO IMPORT AN IMAGE lLE INTO THE *30 PAGE

R ! MVS LPDJH SDJH ÂÓRJR SQJÂ´ ! R " MVS LPDJH Â¿OH ÂÓRJR SQJÂ´ ! R # MVS LQFOXGH SDJH ÂÓRJR SQJÂ´ ! R $ MVS LQFOXGH Â¿OH ÂÓRJR SQJÂ´ ! R % 4HIS #!../4 BE DONE USING A *30 STANDARD ACTION

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Chapter 8. Script-free pages

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'IVEN SDFNDJH FRP H[DPSOH SXEOLF FODVV 0\)XQFWLRQV ^ SXEOLF VWDWLF 6WULQJ UHSHDW LQW [ 6WULQJ VWU ^ PHWKRG ERG\ ` ` AND GIVEN THE *30 # WDJOLE XUL Â´ :(% ,1) P\IXQFWVÂ´ SUHÂ¿[ Â´P\Â´ ! LQVHUW FRGH KHUH ! 7HICH INSERTED AT LINE IN THE *30 IS A VALID %, FUNCTION INVOCATION

R ! ^UHSHDW Â³ Â´ ` R " ^UHSHDW Â³ Â´ Â³ Â´ ` R # ^P\ UHSHDW Â³ Â´ ` R $ ^P\ UHSHDW Â³ Â´ Â³ Â´ ` R % ! VALID INVOCATION #!../4 BE DETERMINED

'IVEN SXEOLF FODVV 0\%HDQ ^ SULYDWH MDYD XWLO 0DS SDUDPV SULYDWH MDYD XWLO /LVW REMHFWV SULYDWH 6WULQJ QDPH SXEOLF MDYD XWLO 0DS JHW3DUDPV ^ UHWXUQ SDUDPV ` SXEOLF 6WULQJ JHW1DPH ^ UHWXUQ QDPH ` SXEOLF MDYD XWLO /LVW JHW2EMHFWV ^ UHWXUQ REMHFWV ` ` 7HICH WILL CAUSE ERRORS ASSUME THAT AN ATTRIBUTE NAMED P\EHDQ CAN BE FOUND AND IS OF TYPE 0\%HDQ #HOOSE ALL THAT APPLY

R ! ^P\EHDQ QDPH` R " ^P\EHDQ>Â³QDPHÂ´@` R # ^P\EHDQ REMHFWV D` R $ ^P\EHDQ>Â³SDUDPVÂ´@ D` R % ^P\EHDQ SDUDPV>Â³DÂ´@` R & ^P\EHDQ>Â³REMHFWVÂ´@ D` \RX DUH KHUH

Chapter 8. Script-free pages

PRFN H[DPV

'IVEN A *30 PAGE 7KH XVHU KDV VXIÂ¿FLHQWO\ ORJJHG LQ RU RXW ^SDUDP ORJJHG,Q RU SDUDP ORJJHG2XW` )F THE REQUEST INCLUDES THE QUERY STRING hORJJHG2XW WUXHÂ´ WHAT WILL BE THIS STATEMENT S DISPLAYED VALUE

R ! 7KH XVHU KDV VXIÂ¿FLHQWO\ ORJJHG LQ RU RXW IDOVH R " 7KH XVHU KDV VXIÂ¿FLHQWO\ ORJJHG LQ RU RXW WUXH R # 7KH XVHU KDV VXIÂ¿FLHQWO\ ORJJHG LQ RU RXW ^SDUDP ORJJHG,Q RU SDUDP ORJJHG2XW`

R $ 7KH XVHU KDV VXIÂ¿FLHQWO\ ORJJHG LQ RU RXW SDUDP ORJJHG,Q RU SDUDP ORJJHG2XW

R % 7KH XVHU KDV VXIÂ¿FLHQWO\ ORJJHG LQ RU RXW RU WUXH

7HICH ABOUT %, ACCESS OPERATORS ARE TRUE #HOOSE ALL THAT APPLY

R ! !NYWHERE THE DOT OPERATOR IS USED THE >@ COULD BE USED INSTEAD

R " !NYWHERE THE >@ OPERATOR IS USED THE DOT COULD BE USED INSTEAD

R # )F THE DOT OPERATOR IS USED TO ACCESS A BEAN PROPERTY BUT THE PROPERTY DOESN T EXIST THEN A RUNTIME EXCEPTION IS THROWN

R $ 4HERE ARE SOME SITUATIONS WHERE THE DOT OPERATOR MUST BE USED AND OTHER SITUATIONS WHERE THE >@ OPERATOR MUST BE USED

4HE FOLLOWING CODE FRAGMENT APPEARS IN A *30 PAGE MVS LQFOXGH SDJH Â´ MVSI KHDGHU KWPOÂ´ ! 4HE *30 PAGE IS PART OF A WEB APPLICATION WITH THE CONTEXT ROOT P\DSS 'IVEN THAT THE APPLICATION S TOP LEVEL DIRECTORY IS P\DSS WHAT IS THE PATH TO THE KHDGHU KWPO lLE

R ! KHDGHU KWPO R " MVSI KHDGHU KWPO R # P\DSS MVSI KHDGHU KWPO R $ LQFOXGHV MVSI KHDGHU KWPO

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Chapter 8. Script-free pages

VFULSWOHVV -63V

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(JSP v2.0 sections 2.2.3)

R ! ^SDUDP KREELHV` R " ^SDUDP9DOXH KREELHV` R # ^SDUDP9DOXHV KREELHV> @` R $ ^SDUDP9DOXHV KREELHV> @` R % ^SDUDP9DOXHV>KREELHV@> @` R & ^SDUDP9DOXHV>KREELHV@> @`

use there -Option B is incorrect beca is no Ă&#x2019;paramValueĂ&#x201C; implicit variable. -Option D is incorrect, arrays are 0 indexed. -Options E and F have incorrect syntax.

'IVEN THAT A WEB APPLICATION STORES THE WEBMASTER EMAIL ADDRESS IN THE SERVLET CONTEXT INITIALIZATION PARAMETER CALLED PDVWHU HPDLO 7HICH RETRIEVES THAT VALUE #HOOSE ALL THAT APPLY

R ! D KUHI ÂśPDLOWR ^LQLW3DUDP PDVWHU HPDLO`Âś! HPDLO PH D!

(JSP v2.0 sections 2.2.3 and 2.3.4)

-Option A is trying to subtract email from master

R " D KUHI ÂśPDLOWR ^FRQWH[W3DUDP PDVWHU HPDLO`Âś! -Option B, there is no HPDLO PH D!

contextParam implicit variable

R # D KUHI ÂśPDLOWR ^LQLW3DUDP>ÂľPDVWHU HPDLOÂś@`Âś! HPDLO PH D!

-Option D, there

is no R $ D KUHI ÂśPDLOWR ^FRQWH[W3DUDP>ÂľPDVWHU HPDLOÂś@`Âś! contextParam implicit variable HPDLO PH D!

\RX DUH KHUH

Chapter 8. Script-free pages

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(JSP v2.0 section 2.6.3)

R ! WDJOLE! WDJ! QDPH!+HOOR QDPH! WDJ FODVV!FRP P\FRPSDQ\ 0\)XQFWLRQV WDJ FODVV! ERG\ FRQWHQW!-63 ERG\ FRQWHQW! WDJ! WDJOLE!

R " WDJOLE!

correct

-Option B uses the syntax. IXQFWLRQ! QDPH!+HOOR QDPH! IXQFWLRQ FODVV!FRP P\FRPSDQ\ 0\)XQFWLRQV IXQFWLRQ FODVV! IXQFWLRQ VLJQDWXUH!MDYD ODQJ 6WULQJ KHOOR MDYD ODQJ 6WULQJ IXQFWLRQ VLJQDWXUH! IXQFWLRQ! WDJOLE!

R # ZHE DSS! VHUYOHW! VHUYOHW QDPH!KHOOR VHUYOHW QDPH! VHUYOHW FODVV!FRP P\FRPSDQ\ 0\)XQFWLRQV VHUYOHW FODVV! VHUYOHW! ZHE DSS!

R $ WDJOLE!

use the -Option D is incorrect becaplete IXQFWLRQ! function signature is incom QDPH!+HOOR QDPH! IXQFWLRQ FODVV!FRP P\FRPSDQ\ 0\)XQFWLRQV IXQFWLRQ FODVV! IXQFWLRQ VLJQDWXUH!KHOOR MDYD ODQJ 6WULQJ IXQFWLRQ VLJQDWXUH! IXQFWLRQ! WDJOLE!

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Chapter 8. Script-free pages

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'IVEN

5.1)

SDFNDJH FRP H[DPSOH SXEOLF FODVV 7KH%HDQ ^ SULYDWH LQW YDOXH SXEOLF 7KH%HDQ ^ YDOXH ` SXEOLF LQW JHW9DOXH ^ UHWXUQ YDOXH ` SXEOLF YRLG VHW9DOXH LQW Y ^ YDOXH Y ` ` !SSUMING NO INSTANCES OF 7KH%HDQ HAVE BEEN CREATED YET WHICH *30 STANDARD ACTION STATEMENTS CREATE A NEW INSTANCE OF THIS BEAN AND STORE IT IN THE REQUEST SCOPE #HOOSE ALL THAT APPLY

R ! MVS XVH%HDQ QDPH Â´P\%HDQÂ´ W\SH Â´FRP H[DPSOH 7KH%HDQÂ´ !

R " MVS PDNH%HDQ QDPH Â´P\%HDQÂ´ W\SH Â´FRP H[DPSOH 7KH%HDQÂ´ !

R # MVS XVH%HDQ LG Â´P\%HDQÂ´ FODVV Â´FRP H[DPSOH 7KH%HDQÂ´ VFRSH Â´UHTXHVWÂ´ !

R $ MVS PDNH%HDQ LG Â´P\%HDQÂ´ FODVV Â´FRP H[DPSOH 7KH%HDQÂ´ VFRSH Â´UHTXHVWÂ´ !

te is -Option A is invalid because the type attribu scope NOT used to create a new instance ands the attribute must be speciĂ&#x17E;ed (or default to page).

-Option B is invalid for all of the above reasons plus jsp:makeBean is NOT a real tag.

-Option D is invalid because jsp:makeBean is NOT a real tag.

'IVEN A -ODEL ARCHITECTURE IN WHICH A *30 PAGE HANDLES ALL OF THE CONTROLLER (JSP FUNCTIONS THAT *30 CONTROLLER NEEDS TO DISPATCH THE REQUEST TO ANOTHER *30 PAGE

v2.0 section 5.5)

7HICH STANDARD ACTION CODE WILL PERFORM THIS DISPATCH

. R ! MVS IRUZDUG SDJH ÂÝLHZ MVSÂ´ ! -Option A is correct (pg 1-110) -Option B is invalid because the R " MVS IRUZDUG ÂżOH ÂÝLHZ MVSÂ´ ! forward action has no Ă&#x17E;le attribute. R # MVS GLVSDWFK SDJH ÂÝLHZ MVSÂ´ ! -Op tion R $ MVS GLVSDWFK ÂżOH ÂÝLHZ MVSÂ´ ! ther s C and D are invalid because

e is no dispatch action.

\RX DUH KHUH

Chapter 8. Script-free pages

PRFN DQVZHUV

(JSP v2.0 section 2.3.4)

'IVEN MDYD XWLO /LVW OLVW QHZ MDYD XWLO $UUD\/LVW OLVW DGG ÂłDÂ´ OLVW DGG Âł Â´ OLVW DGG ÂłFÂ´ UHTXHVW VHW$WWULEXWH ÂłOLVWÂ´ OLVW UHTXHVW VHW$WWULEXWH ÂłOLVW,G[Â´ Âł Â´ ! LQVHUW FRGH KHUH !

7HICH INSERTED AT LINE ARE VALID AND EVALUATE TO F #HOOSE ALL THAT APPLY

R ! ÔLVW ` -Options A and C are incorrect R " ÔLVW> @` because the dot operator cannot R # ÔLVW OLVW,G[ ` be used with a primitive. R $ ÔLVW>OLVW,G[ @` R % ÔLVW>ÂľOLVW,G[Âś @` -Option E is incorrect because R & ÔLVW>OLVW>ÂľOLVW,G[Âś@@` (Ă&#x201D;listIdxĂ&#x2022; + 1) becomes a String.

7HICH STATEMENTS ABOUT THE DOT AND >@ %, OPERATORS ARE TRUE #HOOSE ALL THAT APPLY

(JSP v2.0 pg. 1-69 )

R ! ^IRR EDU` IS EQUIVALENT TO ^IRR>EDU@` -Option A is incorrect because it

should be foo[Ă&#x2019;barĂ&#x201C;].

R " ÎRR EDU` IS EQUIVALENT TO ÎRR>ÂłEDUÂ´@` R # ÎRR>Âł Â´@` IS VALID SYNTAX IF IRR IS A 0DS R $ ^KHDGHU 8VHU $JHQW` IS EQUIVALENT TO ^KHDGHU>8VHU $JHQW@`

R % ^KHDGHU 8VHU $JHQW` IS EQUIVALENT TO

-Options D and E are incorrect because of the dash in User-Agent. Only header[Ă&#x2019;User-AgentĂ&#x201C;] will work.

^KHDGHU>Âł8VHU $JHQWÂ´@`

R & ^IRR> @` IS VALID SYNTAX IF IRR IS A /LVW OR AN ARRAY

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Chapter 8. Script-free pages

VFULSWOHVV -63V

^ ` 7HAT WILL BE DISPLAYED

R ! R " R # R $ R % [ `

(JSP v2.0 pg. 1-71)

'IVEN A *30 PAGE WITH THE LINE

-Option A is correct. The modulus operator returns the remainder of a division operation.

(JSP v2.0 pg 1-67 and pg 1-79)

'IVEN ^SDUDP ÂżUVWQDPH` ^SDUDP PLGGOHQDPH` ^SDUDP ODVWQDPH` ^SDUDP9DOXHV ODVWQDPH> @` 7HICH DESCRIBES THE OUTPUT PRODUCED BY THIS PORTION OF A *30 PAGE WHEN PASSED THE QUERY STRING "ÂżUVWQDPH -RKQ ODVWQDPH 'RH

R ! -RKQ 'RH 13 -Option A is invalid because aslinewell. prints the userĂ&#x2022;s last name R " -RKQ 'RH 'RH R # -RKQ QXOO 'RH -Options C and D are invalid because line 11 R $ -RKQ QXOO 'RH 'RH results in printing nothing rather than Ă&#x2019;nullĂ&#x201C;. R % ! NULL POINTER EXCEPTION WILL BE THROWN

7HICH SHOW VALID USAGE OF %, IMPLICIT VARIABLES #HOOSE ALL THAT APPLY

R ! ^FRRNLHV IRR` R " ^LQLW3DUDP IRR`

(JSP v2.0 pg. 1-66)

-Option A is incorrect because the variable is Ă&#x2019;cookieĂ&#x201C;.

R # ^SDJH&RQWH[W IRR` R $ ^UHTXHVW6FRSH IRR`

-Option C is incorrect because pageContext is NOT a Map and it doesnĂ&#x2022;t have a Ă&#x2019;fooĂ&#x201C; property.

R % ^KHDGHU>Âł8VHU $JHQWÂ´@` R & ^UHTXHVW'LVSDWFKHU IRR` -Option F is incorrect because

this is NOT an implicit object.

R ' ^SDJH&RQWH[W UHTXHVW UHTXHVW85,` \RX DUH KHUH

Chapter 8. Script-free pages

PRFN DQVZHUV

(JSP v2.0 pgs. 1-103 and pg. 1-104)

7HICH ARE TRUE ABOUT THE MVS XVH%HDQ! STANDARD ACTION #HOOSE ALL THAT APPLY

-Option A is incorrect

R ! 4HE LG ATTRIBUTE IS OPTIONAL because id is required. -Options B and C are incorrect R " 4HE VFRSH ATTRIBUTE IS REQUIRED because scope is optional and R # 4HE VFRSH ATTRIBUTE IS OPTIONAL AND DEFAULTS TO UHTXHVW defaults to page. R $ %ITHER THE FODVV OR W\SH ATTRIBUTES MAY BE SPECIlED BUT AT LEAST ONE

R % )T IS VALID TO INCLUDE BOTH THE FODVV ATTRIBUTE AND THE W\SH ATTRIBUTE EVEN IF THEIR VALUES ARE ./4 THE SAME

(JSP v2.0 section

(OW WOULD YOU INCLUDE DYNAMIC CONTENT IN A *30 SIMILAR TO A SERVER SIDE INCLUDE 33) #HOOSE ALL THAT APPLY

R ! # LQFOXGH ÂżOH Â´ VHJPHQWV IRRWHU MVSIÂ´ ! R " MVS IRUZDUG SDJH Â´ VHJPHQWV IRRWHU MVSIÂ´ ! R # MVS LQFOXGH SDJH Â´ VHJPHQWV IRRWHU MVSIÂ´ ! R $ 5HTXHVW'LVSDWFKHU GLVSDWFKHU

5.4)

-Option A is incorrect because it uses an include directive, which is for static includes that happen at translation time.

UHTXHVW JHW5HTXHVW'LVSDWFKHU Âł VHJPHQWV IRRWHU MVSIÂ´ GLVSDWFKHU LQFOXGH UHTXHVW UHVSRQVH

-Option D would be correct if it was a scriptlet: it functionally does the same thing as option C, but its syntax is only used by servlets.

)N AN (4-, PAGE WITH A RICH GRAPHICAL LAYOUT WHICH *30 STANDARD ACTION CAN BE USED TO IMPORT AN IMAGE lLE INTO THE *30 PAGE

(JSP v2.0 section

5.4)

because

alid R ! MVS LPDJH SDJH Â´ORJR SQJÂ´ ! -Options A and B are inv standard action. there is no image

R " MVS LPDJH ÂżOH Â´ORJR SQJÂ´ ! R # MVS LQFOXGH SDJH Â´ORJR SQJÂ´ !

e syntax of , not because th ause it does -Option C is invalid bec but , ong is wr data of the include action ary bin e th ort to imp . not make senseint nt te con P JS e the image Ă&#x17E;le o th

R $ MVS LQFOXGH ÂżOH Â´ORJR SQJÂ´ ! R % 4HIS #!../4 BE DONE USING A *30 STANDARD ACTION

the include -Option D is invalid because attr ibute. action does not take a Ă&#x17E;le This is a tricky question because it is NOT possible to import the contents of any binary Ă&#x17E;le into a JSP page, which generates an HTML response.

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Chapter 8. Script-free pages

VFULSWOHVV -63V

(JSP v2.0 section 2.6)

'IVEN

SDFNDJH FRP H[DPSOH SXEOLF FODVV 0\)XQFWLRQV ^ SXEOLF VWDWLF 6WULQJ UHSHDW LQW [ 6WULQJ VWU ^ PHWKRG ERG\ ` ` AND GIVEN THE *30 # WDJOLE XUL Â´ :(% ,1) P\IXQFWVÂ´ SUHÂż[ Â´P\Â´ ! LQVHUW FRGH KHUH ! 7HICH INSERTED AT LINE IN THE *30 IS A VALID %, FUNCTION INVOCATION

R ! ^UHSHDW Âł Â´ ` R " ^UHSHDW Âł Â´ Âł Â´ ` R # ^P\ UHSHDW Âł Â´ ` . The -Option E is correct R $ ^P\ UHSHDW Âł Â´ Âł Â´ ` necessary mapping information R % ! VALID INVOCATION #!../4 BE DETERMINED is NOT known.

'IVEN

(JSP v2.0 pg. 1-68)

SXEOLF FODVV 0\%HDQ ^ SULYDWH MDYD XWLO 0DS SDUDPV SULYDWH MDYD XWLO /LVW REMHFWV SULYDWH 6WULQJ QDPH SXEOLF MDYD XWLO 0DS JHW3DUDPV ^ UHWXUQ SDUDPV ` SXEOLF 6WULQJ JHW1DPH ^ UHWXUQ QDPH ` SXEOLF MDYD XWLO /LVW JHW2EMHFWV ^ UHWXUQ REMHFWV ` ` 7HICH WILL CAUSE ERRORS ASSUME THAT AN ATTRIBUTE NAMED P\EHDQ CAN BE FOUND AND IS OF TYPE 0\%HDQ #HOOSE ALL THAT APPLY

R ! ^P\EHDQ QDPH` R " ^P\EHDQ>ÂłQDPHÂ´@` R # ^P\EHDQ REMHFWV D` R $ ^P\EHDQ>ÂłSDUDPVÂ´@ D` R % ^P\EHDQ SDUDPV>ÂłDÂ´@` R & ^P\EHDQ>ÂłREMHFWVÂ´@ D`

-Options C and F will cause errors. Ă&#x2019;aĂ&#x201C; is NOT a List property, and since Ă&#x2019;objectsĂ&#x201C; is NOT a Map, a lookup wonĂ&#x2022;t be performed (as opposed to D and E).

\RX DUH KHUH

Chapter 8. Script-free pages

PRFN DQVZHUV

(JSP v2.0 pgs 1-66 and 1-73)

'IVEN A *30 PAGE 7KH XVHU KDV VXIÂżFLHQWO\ ORJJHG LQ RU RXW ^SDUDP ORJJHG,Q RU SDUDP ORJJHG2XW`

)F THE REQUEST INCLUDES THE QUERY STRING hORJJHG2XW WUXHÂ´ WHAT WILL BE THIS STATEMENT S DISPLAYED VALUE

R ! 7KH XVHU KDV VXIÂżFLHQWO\ ORJJHG LQ RU RXW IDOVH R " 7KH XVHU KDV VXIÂżFLHQWO\ ORJJHG LQ RU RXW WUXH -Option B is correct because the EL expression using Ă&#x2019;orĂ&#x201C; R # 7KH XVHU KDV VXIÂżFLHQWO\ ORJJHG LQ RU RXW ^SDUDP true if either ORJJHG,Q RU SDUDP ORJJHG2XW`

R $ 7KH XVHU KDV VXIÂżFLHQWO\ ORJJHG LQ RU RXW SDUDP

will return loggedIn or loggedOut is true.

ORJJHG,Q RU SDUDP ORJJHG2XW

R % 7KH XVHU KDV VXIÂżFLHQWO\ ORJJHG LQ RU RXW RU WUXH

(JSP v2.0 pg. 1-69)

7HICH ABOUT %, ACCESS OPERATORS ARE TRUE #HOOSE ALL THAT APPLY

R ! !NYWHERE THE DOT OPERATOR IS USED THE >@ COULD BE USED INSTEAD

-Option B is incorrect because only b) a) Lists and arrays, and form whose keys are not well- ed.

R " !NYWHERE THE >@ OPERATOR IS USED THE DOT COULD BE USED the [] will work when accessing Maps INSTEAD

R # )F THE DOT OPERATOR IS USED TO ACCESS A BEAN PROPERTY BUT THE PROPERTY DOESN T EXIST THEN A RUNTIME EXCEPTION IS THROWN

ause

ption D is incorrect bec be R $ 4HERE ARE SOME SITUATIONS WHERE THE DOT OPERATOR MUST BE -O the dot operator can alwaysor. USED AND OTHER SITUATIONS WHERE THE >@ OPERATOR MUST BE USED

converted to the [] operat

4HE FOLLOWING CODE FRAGMENT APPEARS IN A *30 PAGE MVS LQFOXGH SDJH Â´ MVSI KHDGHU KWPOÂ´ !

(JSP v2.0 section

5.4)

4HE *30 PAGE IS PART OF A WEB APPLICATION WITH THE CONTEXT ROOT P\DSS 'IVEN THAT THE APPLICATION S TOP LEVEL DIRECTORY IS P\DSS WHAT IS THE PATH TO THE KHDGHU KWPO lLE

R ! KHDGHU KWPO R " MVSI KHDGHU KWPO R # P\DSS MVSI KHDGHU KWPO R $ LQFOXGHV MVSI KHDGHU KWPO

as -The path /jspf/header.html when used the value of the <jsp:include> actionĂ&#x2022;s page tion, attribute is relative to the web applicaat theso a leading back slash (Ă&#x2019;/Ă&#x201C;) means Ă&#x2019;begin applicationĂ&#x2022;s top level.Ă&#x201C;

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Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful Head First Servlets and JSP By Bert Bates, Kathy Sierra, Bryan Basham ISBN: 0596005407 Publisher: O'Reilly Prepared for Stephen Goss, Safari ID: stephengoss@gmx.net Print Publication Date: 8/1/2004 User number: 747221 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited.

Chapter 9. Custom tags are powerful

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!LL OF THE OBJECTIVES IN THIS SECTION ARE COVERED IN THIS CHAPTER ALTHOUGH SOME OF THE CONTENT IS COVERED AGAIN IN THE NEXT CHAPTER $EVELOPING #USTOM 4AGS

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Chapter 9. Custom tags are powerful

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-4 IVL [\IVLIZL IK\QWV[ IZM TQUQ\ML 7HAT HAPPENS WHEN YOU BUMP INTO A BRICK WALL 9OU CAN GO BACK TO SCRIPTING OF COURSEÂ&#x2C6;BUT YOU KNOW THAT S NOT THE PATH $EVELOPERS USUALLY WANT WAY MORE STANDARD ACTIONS ORÂ&#x2C6;EVEN BETTERÂ&#x2C6;THE ABILITY TO CREATE THEIR OWN ACTIONS 4HAT S WHAT CUSTOM TAGS ARE FOR )NSTEAD OF SAYING JSP SET0ROPERTY YOU WANT TO DO SOMETHING LIKE MY DO#USTOM4HING !ND YOU CAN "UT IT S NOT THAT EASY TO CREATE THE SUPPORT CODE THAT GOES BEHIND THE TAG &OR THE *30 PAGE CREATOR CUSTOM TAGS ARE MUCH EASIER TO USE THAN SCRIPTING &OR THE *AVA PROGRAMMER HOWEVER BUILDING THE CUSTOM TAG HANDLER THE *AVA CODE INVOKED WHEN A *30 USES THE TAG IS TOUGHER &ORTUNATELY THERE S A STANDARD LIBRARY OF CUSTOM TAGS KNOWN AS THE *30 3TANDARD 4AG ,IBRARY *34, 'IVEN THAT YOUR *30 SHOULDN T BE DOING A BUNCH OF BUSINESS LOGIC ANYWAY YOU MIGHT lND THAT THE *34, COMBINED WITH %, IS ALL YOU LL EVER NEED 3TILL THERE COULD BE TIMES WHEN YOU NEED SOMETHING FROM SAY A CUSTOM TAG LIBRARY DEVELOPED SPECIlCALLY FOR YOUR COMPANY )N THIS CHAPTER YOU LL LEARN HOW TO USE THE CORE *34, TAGS AS WELL AS CUSTOM TAGS FROM OTHER LIBRARIES )N THE NEXT CHAPTER WE LL LEARN HOW TO ACTUALLY BUILD THE CLASSES THAT HANDLE CALLS TO THE CUSTOM TAGS SO THAT YOU CAN DEVELOP YOUR OWN

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Chapter 9. Custom tags are powerful

WKH F IRU(DFK! WDJ

4WWXQVO _Q\PW]\ [KZQX\QVO )MAGINE YOU WANT SOMETHING THAT LOOPS OVER A COLLECTION SAY AN ARRAY OF CATALOG ITEMS PULLS OUT ONE ELEMENT AT A TIME AND PRINTS THAT ELEMENT IN A DYNAMICALLY GENERATED TABLE ROW 9OU CAN T POSSIBLY HARD CODE THE COMPLETE TABLEÂ&#x2C6;YOU HAVE NO IDEA HOW MANY ROWS THERE WILL BE AT RUNTIME AND OF COURSE YOU DON T KNOW THE VALUES IN THE COLLECTION 4HE C FOR%ACH TAG IS THE ANSWER 4HIS DOES REQUIRE A VERY SLIGHT KNOWLEDGE OF (4-, TABLES BUT WE VE INCLUDED NOTES HERE FOR THOSE WHO AREN T FAMILIAR WITH THE TOPIC "Y THE WAY ON THE EXAM YOU ARE EXPECTED TO KNOW HOW TO USE C FOR%ACH WITH TABLES

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Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful

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,MKWV[\Z]K\QVO $K"NWZ-IKP& 4HE C FOR%ACH TAG MAPS NICELY INTO A FOR LOOPÂ&#x2C6;THE TAG REPEATS THE BODY OF THE TAG FOR EACH ELEMENT IN THE COLLECTION AND WE USE hCOLLECTIONv HERE TO MEAN EITHER AN ARRAY OR #OLLECTION OR -AP OR COMMA DELIMITED 3TRING 4HE KEY FEATURE IS THAT THE TAG ASSIGNS EACH ELEMENT IN THE COLLECTION TO THE VARIABLE YOU DECLARE WITH THE VAR ATTRIBUTE

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Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful

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(OW DID YOU KNOW THAT THE hVAR3TATUSv ATTRI BUTE WAS AN INSTANCE OF WHATEVER THAT WAS AND HOW DID YOU KNOW THAT IT HAS A hCOUNTv PROPERTY

!HHHH WE LOOKED IT UP

)T S ALL THERE IN THE *34, SPEC )F YOU DON T HAVE THE SPEC ALREADY GO DOWNLOAD IT ./7 THE INTRO OF THIS BOOK TELLS YOU WHERE TO GET THE SPECS COVERED ON THE EXAM )T IS 4(% REFERENCE FOR ALL THE TAGS IN THE *34, AND TELLS YOU ALL THE POSSIBLE ATTRIBUTES WHETHER THEY RE OPTIONAL OR REQUIRED THE ATTRIBUTE TYPE AND ANY OTHER DETAILS ON HOW YOU USE THE TAG %VERYTHING YOU NEED TO KNOW ABOUT THESE TAGS FOR THE EXAM IS IN THIS CHAPTER "UT SOME OF THE TAGS HAVE A FEW MORE OPTIONS THAN WE COVER HERE SO YOU MIGHT WANT TO HAVE A LOOK IN THE SPEC

3INCE YOU KNOW MORE THAN YOU RE TELLING ABOUT THIS TAG DOES IT GIVE YOU A WAY TO CHANGE THE ITERATION STEPS )N A REAL *AVA FOR LOOP ) DON T HAVE TO DO I ) CAN DO I FOR EXAMPLE TO GET EVERY THIRD ELEMENT INSTEAD OF EVERY ELEMENT

.OT A PROBLEM 4HE C FOR%ACH TAG HAS OPTIONAL ATTRIBUTES FOR BEGIN END IN CASE YOU WANT TO ITERATE OVER A SUBSET OF THE COLLECTION AND STEP IF YOU WANT TO SKIP OVER SOME ELEMENTS

)S THE hCv IN C FOR%ACH A REQUIRED PREl X

7ELL SOME PREFIX IS REQUIRED OF COURSE ALL TAGS AND %, FUNCTIONS MUST HAVE A PREFIX TO GIVE THE #ONTAIN ER THE NAMESPACE FOR THAT TAG OR FUNCTION NAME "UT YOU DON T (!6% TO NAME THE PREFIX hCv )T S JUST THE STANDARD CONVENTION FOR THE SET OF TAGS IN *34, KNOWN AS hCOREv 7E RECOMMEND USING SOMETHING OTHER THAN hCv AS A PREFIX WHENEVER YOU WANT TO TOTALLY CONFUSE THE PEOPLE YOU WORK WITH

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Chapter 9. Custom tags are powerful

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,WQVO I KWVLQ\QWVIT QVKT]LM _Q\P $K"QN& )MAGINE YOU HAVE A PAGE WHERE USERS CAN VIEW COMMENTS FROM OTHER USERS !ND IMAGINE THAT MEMBERS CAN ALSO POST COMMENTS BUT NON MEMBER GUESTS CANNOT 9OU WANT EVERYONE TO GET THE SAME PAGE BUT YOU WANT MEMBERS TO hSEEv MORE THINGS ON THE PAGE 9OU WANT A CONDITIONAL JSP INCLUDE AND OF COURSE YOU DON T WANT TO DO IT WITH SCRIPTING :KDW PHPEHUV VHH

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Yes, those are SINGLE quotes around Ă&#x201D;memberĂ&#x2022;. DonĂ&#x2022;t forget that you can use EITHER double or single quotes in your tags and EL.

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*]\ _PI\ QN aW] VMML IV MT[M ' 7HAT IF YOU WANT TO DO ONE THING IF THE CONDITION IS TRUE AND A DIFFERENT THING IF THE CONDITION IS FALSE )N OTHER WORDS WHAT IF WE WANT TO SHOW EITHER ONE THING OR THE OTHER BUT NOBODY WILL SEE BOTH 4HE C IF ON THE PREVIOUS PAGE WORKED l NE BECAUSE THE LOGIC WAS EVERYBODY SEES THE l RST PART AND THEN IF THE TEST CONDITION IS TRUE SHOW A LITTLE EXTRA "UT NOW IMAGINE THIS SCENARIO YOU HAVE A CAR SALES WEB SITE AND YOU WANT TO CUSTOMIZE THE HEADLINE THAT SHOWS UP ON EACH PAGE BASED ON A USER ATTRIBUTE SET UP EARLIER IN THE SESSION -OST OF THE PAGE IS THE SAME REGARDLESS OF THE USER BUT EACH USER SEES A CUSTOMIZED HEADLINE Â&#x2C6;ONE THAT BEST l TS THE USER S PERSONAL MOTIVATION FOR BUYING 7E ARE AFTER ALL TRYING TO SELL HIM A CAR AND BECOME OBSCENELY WEALTHY !T THE BEGINNING OF THE SESSION A FORM ASKS THE USER TO CHOOSE WHAT S MOST IMPORTANT $W WKH EHJLQQLQJ RI WKH VHVVLRQ KWWS ORFDOKRVW WHVW-63 7HVWHU GR

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Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful

XVLQJ -67/

<PM $K"[M\& \IO [W U]KP KWWTMZ \PIV $R[X"[M\8ZWXMZ\a& 4HE JSP SET0ROPERTY TAG CAN DO ONLY ONE THINGÂ&#x2C6;SET THE PROPERTY OF A BEAN "UT WHAT IF YOU WANT TO SET A VALUE IN A -AP 7HAT IF YOU WANT TO MAKE A NEW ENTRY IN A -AP /R WHAT IF YOU SIMPLY WANT TO CREATE A NEW REQUEST SCOPED ATTRIBUTE 9OU GET ALL THAT WITH C SET BUT YOU HAVE TO LEARN A FEW SIMPLE RULES 3ET COMES IN TWO m AVORS VAR AND TARGET 4HE VAR VERSION IS FOR SETTING ATTRIBUTE VARIABLES THE TARGET VERSION IS FOR SETTING BEAN PROPERTIES OR -AP VALUES %ACH OF THE TWO m AVORS COMES IN TWO VARIATIONS WITH OR WITHOUT A BODY 4HE C SET BODY IS JUST ANOTHER WAY TO PUT IN THE VALUE

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Chapter 9. Custom tags are powerful

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=[QVO $K"[M\& _Q\P JMIV[ IVL 5IX[ 4HIS m AVOR OF C SET WITH ITS TWO VARIATIONSÂ&#x2C6;WITH AND WITHOUT A BODY WORKS FOR ONLY TWO THINGS BEAN PROPERTIES AND -AP VALUES 4HAT S IT 9OU CAN T USE IT TO ADD THINGS TO LISTS OR ARRAYS )T S SIMPLEÂ&#x2C6;YOU GIVE IT THE OBJECT A BEAN OR -AP THE PROPERTY KEY NAME AND THE VALUE

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Chapter 9. Custom tags are powerful

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3Ma XWQV\[ IVL OW\KPI[ _Q\P $K"[M\& 9ES C SET IS EASY TO USE BUT THERE ARE A FEW DEAL BREAKERS YOU HAVE TO REMEMBER

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Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful

XVLQJ -67/

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Chapter 9. Custom tags are powerful

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?Q\P $K"QUXWZ\& \PMZM IZM VW_ <0:-- _Ia[ \W QVKT]LM KWV\MV\ 3O FAR WE VE USED TWO DIFFERENT WAYS TO ADD CONTENT FROM ANOTHER RESOURCE INTO A *30 "UT THERE S YET ANOTHER WAY USING *34,

7KH LQFOXGH GLUHFWLYH # LQFOXGH Âż OH Â´+HDGHU KWPOÂ´ ! 3TATIC ADDS THE CONTENT FROM THE VALUE OF THE l LE ATTRIBUTE TO THE CURRENT PAGE AT TRANSLATION TIME

7KH MVS LQFOXGH! VWDQGDUG DFWLRQ MVS LQFOXGH SDJH Â´+HDGHU MVSÂ´ ! $YNAMIC ADDS THE CONTENT FROM THE VALUE OF THE PAGE ATTRIBUTE TO THE CURRENT PAGE AT REQUEST TIME

7KH F LPSRUW! -67/ WDJ

includes, other two Unlike theport> url can be from the <c:im he web Container! outside t

F LPSRUW XUO Â´KWWS ZZZ ZLFNHGO\VPDUW FRP VN\OHU KRUVH KWPOÂ´ ! $YNAMIC ADDS THE CONTENT FROM THE VALUE OF THE 52, ATTRIBUTE TO THE CURRENT PAGE AT REQUEST TIME )T WORKS A LOT LIKE JSP INCLUDE BUT IT S MORE POWERFUL AND m EXIBLE

Do NOT confuse <c:import> (a type of include) with the Ă&#x2019;importĂ&#x201C; attribute of the page directive (a way to put a Java import statement in the generated servlet).

W DWWULEXWH QDPHV 7KH\ DOO KDYH GLIIHUHQ FOXGHÂľ YV Â´LPSRUWÂľ

U Â´LQ W IR K RX DWF $QG Z U -63 XVHV D DQRWKHU UHVRXUFH LQWR \RX V IRU LQFOXGLQJ FRQWHQW IURP QFOXGH! XVHV SDJH DQG MVS L KH (DFK RI WKH WKUHH PHFKDQLVP OH W HV Âż H XV WH 7KH LQFOXGH GLUHFWLY W \RX GR KDYH GLIIHUHQW ZRUG IRU WKH DWWULEX KHQ \RX WKLQN DERXW LW EX 0/ HV XUO 7KLV PDNHV VHQVH Z LF OD\RXW WHPSODWHV OLNH +7 VWDW WKH -67/ F LPSRUW! WDJ XV G IRU HQGH \ LQW LQDOO GLUHFWLYH ZDV RULJ PRUH IRU G\QDPLF FRQWHQW WR PHPRUL]H DOO WKUHH 7KH QGHG LQWH ZDV XGH! LQFO OHÂ´ 7KH MVS IRU F LPSRUW! KHDGHUV ,Q RWKHU ZRUGV D ÂłÂż R UHĂ&#x20AC; HFW WKDW 7KH DWWULEXWH QDPHG WKH DWWULEXWH ÂłSDJHÂ´ W ÂśW JR RXWVLGH FRPLQJ IURP -63V VR WKH\ U WKH Âż UVW WZR ÂłLQFOXGHVÂ´ FDQ PEH HPH / 5 D 85 H LWÂ˛ X JLY LV QDPHG IRU H[DFWO\ ZKDW \R F LPSRUW! FDQ WKH FXUUHQW &RQWDLQHU EXW

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Chapter 9. Custom tags are powerful

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$K"QUXWZ\& KIV ZMIKP 7=<;1,- \PM _MJ IXX 7ITH JSP INCLUDE OR THE INCLUDE DIRECTIVE YOU CAN INCLUDE ONLY PAGES THAT ARE PART OF THE CURRENT WEB APP "UT NOW WITH C IMPORT YOU HAVE THE OPTION TO PULL IN CONTENT FROM OUTSIDE THE #ONTAINER 4HIS SIMPLE EXAMPLE SHOWS A *30 ON 3ERVER ! IMPORTING THE CONTENTS OF A 52, ON 3ERVER " !T REQUEST TIME THE (4-, CHUNK IN THE IMPORTED l LE IS ADDED TO THE *30 4HE IMPORTED CHUNK USES A REFERENCE TO AN IMAGE THAT IS ALSO ON 3ERVER " 6HUYHU $ WKH -63 GRLQJ WKH LPSRUW

7KH -63 # WDJOLE SUHÂż [ Â´FÂ´ XUL Â´KWWS MDYD VXQ FRP MVS MVWO FRUHÂ´ ! KWPO! ERG\! F LPSRUW XUO Â´KWWS ZZZ ZLFNHGO\VPDUW FRP VN\OHU KRUVH KWPOÂ´ ! EU! 7KLV LV P\ KRUVH ERG\! KWPO!

6HUYHU % WKH LPSRUWHG FRQWHQW

(DonĂ&#x2022;t forget: as with other include mechanisms, thea thing you import should be an HTML fragment and NOT tags.) complete page with opening and closing <html><body>

7KH LPSRUWHG Ă&#x20AC; OH

LPJ VUF Â´KWWS ZZZ ZLFNHGO\VPDUW FRP VN\OHU KRUVH JLIÂ´!

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ming The horse is co ely from a complet rver different web sethat an the page xt. th 7KLV LV P\ KRUVH contains the te

Ă&#x2019;horse.htmlĂ&#x201C; and Ă&#x2019;horse.gifĂ&#x201C; are both on Server B, a completely different web server from the one with the JSP.

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+][\WUQbQVO \PM \PQVO aW] QVKT]LM 2EMEMBER IN THE PREVIOUS CHAPTER WHEN WE DID A JSP INCLUDE TO PUT IN THE LAYOUT HEADER A GRAPHIC WITH SOME TEXT BUT WE WANTED TO CUSTOMIZE THE SUBTITLE USED IN THE HEADER 7E USED JSP PARAM TO MAKE THAT HAPPEN

7KH -63 ZLWK WKH MVS LQFOXGH! KWPO! ERG\! MVS LQFOXGH SDJH Â´+HDGHU MVSÂ´! MVS SDUDP QDPH Â´VXE7LWOHÂ´ YDOXH Â´:H WDNH WKH VWLQJ RXW RI 62$3 Â´ ! MVS LQFOXGH! EU! HP!:HOFRPH WR RXU :HE 6HUYLFHV 6XSSRUW *URXS HP! EU! EU! &RQWDFW XV DW ^LQLW3DUDP PDLQ(PDLO` ( ERG\! KWPO

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KWWS ORFDOKRVW WHVWV &RQWDFW MVS

le Ã&#x2019;We We made the subtit ilable to take the sting...Ã&#x201C; avasetting it the header JSP by ameter. as a new request par

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Chapter 9. Custom tags are powerful

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,WQVO \PM [IUM \PQVO _Q\P $K"XIZIU& (ERE WE ACCOMPLISH THE SAME THING WE DID ON THE PREVIOUS PAGE BUT USING A COMBINATION OF C IMPORT AND C PARAM 9OU LL SEE THAT THE STRUCTURE IS VIRTUALLY IDENTICAL TO THE ONE WE USED WITH STANDARD ACTIONS

7KH -63 ZLWK WKH MVS LQFOXGH! # WDJOLE SUHÂż [ Â´FÂ´ XUL Â´KWWS MDYD VXQ FRP MVS MVWO FRUHÂ´ ! KWPO! ERG\! the F LPSRUW XUO Â´+HDGHU MVSÂ´ !

W No slash, because NO tag has a body...

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ange at all. It This page doesnĂ&#x2022;tWchthe parameter got HO re doesnĂ&#x2022;t ca s there. there, as long as itĂ&#x2022;

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Chapter 9. Custom tags are powerful

XVLQJ -67/

$K"]ZT& NWZ ITT aW]Z PaXMZTQVS VMML[ 2EMEMBER WAY BACK IN OUR OLD SERVLET DAYS WHEN WE WANTED TO USE A SESSION &IRST WE HAD TO GET THE SESSION EITHER THE EXISTING ONE OR A NEW ONE !T THAT POINT THE #ONTAINER KNOWS THAT IT S SUPPOSED TO ASSOCIATE THE CLIENT FROM THIS REQUEST WITH A PARTICULAR SESSION )$ 4HE #ONTAINER WANTS TO USE A COOKIEÂ&#x2C6;IT WANTS TO INCLUDE A UNIQUE COOKIE WITH THE RESPONSE AND THEN THE CLIENT WILL SEND THAT COOKIE BACK WITH EACH SUBSEQUENT REQUEST %XCEPT ONE PROBLEM THE CLIENT MIGHT HAVE A BROWSER WITH COOKIES DISABLED 4HEN WHAT 4HE #ONTAINER WILL AUTOMATICALLY FALL BACK TO 52, REWRITING IF IT DOESN T GET A COOKIE FROM THE CLIENT "UT WITH SERVLETS YOU 34),, HAVE TO ENCODE YOUR 52,S )N OTHER WORDS YOU STILL HAVE TO TELL THE #ONTAINER TO hAPPEND THE JSESSIONID TO THE END OF THIS PARTICULAR 52, v FOR EACH 52, WHERE IT MATTERS 7ELL YOU CAN DO THE SAME THING FROM A *30 USING THE C URL TAG 85/ UHZULWLQJ IURP D VHUYOHW SXEOLF YRLG GR*HW +WWS6HUYOHW5HTXHVW UHTXHVW +WWS6HUYOHW5HVSRQVH UHVSRQVH WKURZV ,2([FHSWLRQ 6HUYOHW([FHSWLRQ ^ UHVSRQVH VHW&RQWHQW7\SH ÂłWH[W KWPOÂ´ 3ULQW:ULWHU RXW UHVSRQVH JHW:ULWHU +WWS6HVVLRQ VHVVLRQ UHTXHVW JHW6HVVLRQ RXW SULQWOQ Âł KWPO! ERG\!Â´ RXW SULQWOQ Âł D KUHI ?Â´Â´ UHVSRQVH HQFRGH85/ Âł %HHU7HVW GRÂ´ Âł?Â´!FOLFN D!Â´ RXW SULQWOQ Âł ERG\! KWPO!Â´ ` to this URL.

Add the extra session ID info

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?PI\ QN \PM =:4 VMML[ MVKWLQVO' 2EMEMBER THAT IN AN (440 '%4 REQUEST THE PARAMETERS ARE APPENDED TO THE 52, AS A QUERY STRING &OR EXAMPLE IF A FORM ON AN (4-, PAGE HAS TWO TEXT l ELDSÂ&#x2C6;l RST NAME AND LAST NAMEÂ&#x2C6;THE REQUEST 52, WILL STICK THE PARAMETER NAMES AND VALUES ON TO THE END OF THE REQUEST 52, "UT AN (440 REQUEST WON T WORK CORRECTLY IF IT CONTAINS UNSAFE CHARACTERS ALTHOUGH MOST MODERN BROWSERS WILL TRY TO COMPENSATE FOR THIS )F YOU RE A WEB DEVELOPER THIS IS OLD NEWS BUT IF YOU RE NEW TO WEB DEVELOPMENT YOU NEED TO KNOW THAT 52,S OFTEN NEED TO BE ENCODED 52, ENCODING MEANS REPLACING THE UNSAFE RESERVED CHARACTERS WITH OTHER CHARACTERS AND THEN THE WHOLE THING IS DECODED AGAIN ON THE SERVER SIDE &OR EXAMPLE SPACES AREN T ALLOWED IN A 52, BUT YOU CAN SUBSTITUTE A PLUS SIGN h v FOR THE SPACE 4HE PROBLEM IS C URL DOES ./4 AUTOMATICALLY ENCODE YOUR 52,S 8VLQJ F XUO! ZLWK D TXHU\ VWULQJ 2EMEMBER THE C URL TAG DOES 52, REWRITING BUT NOT 52, ENCODING F VHW YDU Â´ODVWÂ´ YDOXH Â´+LGGHQ &XUVRUÂ´ ! F VHW YDU Â´Âż UVWÂ´ YDOXH Â´&URXFKLQJ 3L[HOVÂ´ !

Ă&#x2019;varĂ&#x201C; Use the optionalyou want attribute whenvalue later... access to this

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ause <c:param> Now weĂ&#x2022;re safe, becenc oding! e th takes care of

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Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful

XVLQJ -67/

,W ZLOO WDNH PH )25(9(5 WR SXW SDJH GLUHFWLYHV LQ DOO P\ -63V WR VSHFLI\ WKH HUURU SDJH WR XVH $QG ZKDW LI , ZDQW D GLIIHUHQW HUURU SDJH GHSHQGLQJ RQ WKH HUURU" ,I RQO\ WKHUH ZHUH D ZD\ WR FRQÃ&#x20AC; JXUH HUURU SDJHV IRU WKH ZKROH ZHE DSS

;PM LWM[VÂ¼\ SVW_ IJW]\ \PM $MZZWZ XIOM& ,, \IO 9OU CAN DECLARE ERROR PAGES IN THE $$ FOR THE ENTIRE WEB APP AND YOU CAN EVEN CONl GURE DIFFERENT ERROR PAGES FOR DIFFERENT EXCEPTION TYPES OR (440 ERROR CODE TYPES ETC 4HE #ONTAINER USES ERROR PAGE CONl GURATION IN THE $$ AS THE DEFAULT BUT IF A *30 HAS AN EXPLICIT ERROR0AGE PAGE DIRECTIVE THE #ONTAINER USES THE DIRECTIVE

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Chapter 9. Custom tags are powerful

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+WVNQO]ZQVO MZZWZ XIOM[ QV \PM ,, 9OU CAN DECLARE ERROR PAGES IN THE $$ BASED ON EITHER THE EXCEPTION TYPE OR THE (440 STATUS ERROR CODE NUMBER 4HAT WAY YOU CAN SHOW THE CLIENT DIFFERENT ERROR PAGES SPECIlC TO THE TYPE OF THE PROBLEM THAT GENERATED THE ERROR

'HFODULQJ D FDWFK DOO HUURU SDJH 4HIS APPLIES TO EVERYTHING IN YOUR WEB APPÂ&#x2C6;NOT JUST *30S 9OU CAN OVERRIDE IT IN INDIVIDUAL *30S BY ADDING A PAGE DIRECTIVE WITH AN ERROR0AGE ATTRIBUTE HUURU SDJH! H[FHSWLRQ W\SH!MDYD ODQJ 7KURZDEOH H[FHSWLRQ W\SH! ORFDWLRQ! HUURU3DJH MVS ORFDWLRQ! HUURU SDJH!

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root/context, which relative to the web-appreg ardless of whether The <location> MUST be e tru is is (Th h a slash. -type>.) tion means it MUST start wit cep <ex or de> ror-co the error page is based on <er

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Chapter 9. Custom tags are powerful

XVLQJ -67/

-ZZWZ XIOM[ OM\ IV M`\ZI WJRMK\" M`KMX\QWV !N ERROR PAGE IS ESSENTIALLY THE *30 THAT HANDLES THE EXCEPTION SO THE #ONTAINER GIVES THE PAGE AN EXTRA OBJECT FOR THE EXCEPTION 9OU PROBABLY WON T WANT TO SHOW THE EXCEPTION TO THE USER BUT YOU VE GOT IT )N A SCRIPTLET YOU CAN USE THE IMPLICIT OBJECT EXCEPTION AND FROM A *30 YOU CAN USE THE %, IMPLICIT OBJECT [PAGE#ONTEXT EXCEPTION] 4HE OBJECT IS TYPE JAVA LANG 4HROWABLE SO IN A SCRIPT YOU CAN CALL METHODS AND WITH %, YOU CAN ACCESS THE STACK4RACE AND MESSAGE PROPERTIES Note:

the exception implicit object is available ONLY to error pages with an explicitly-deĂ&#x17E;ned page directive:

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If this prints out, then we KNOW we made it past the exception (which in this example, means we successfully caught the exception).

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Chapter 9. Custom tags are powerful

XVLQJ -67/

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Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful

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?PI\ QN aW] VMML I \IO \PI\Âź[ 67< QV 2;<4' 4HE *34, IS HUGE 6ERSION HAS lVE LIBRARIESÂ&#x2C6;FOUR WITH CUSTOM TAGS AND ONE WITH A BUNCH OF FUNCTIONS FOR 3TRING MANIPULATION 4HE TAGS WE COVER IN THIS BOOK WHICH HAPPEN TO BE THE ONES YOU RE EXPECTED TO KNOW FOR THE EXAM ARE FOR THE GENERIC THINGS YOU RE MOST LIKELY TO NEED BUT IT S POSSIBLE THAT BETWEEN ALL lVE LIBRARIES YOU LL lND EVERYTHING YOU MIGHT EVER NEED /N THE NEXT PAGE WE LL START LOOKING AT WHAT HAPPENS WHEN THE TAGS BELOW AREN T ENOUGH 7KH Â´&RUHÂľ OLEUDU\

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Chapter 9. Custom tags are powerful

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=[QVO I \IO TQJZIZa \PI\Â¼[ 67< NZWU \PM 2;<4 #REATING THE CODE THAT GOES BEHIND A TAG IN OTHER WORDS THE *AVA CODE THAT S INVOKED WHEN YOU PUT THE TAG IN YOUR *30 ISN T TRIVIAL 7E HAVE A WHOLE CHAPTER THE NEXT ONE DEVOTED TO DEVELOPING YOUR OWN CUSTOM TAG HANDLERS "UT THE LAST PART OF THIS CHAPTER IS ABOUT HOW TO USE CUSTOM TAGS 7HAT HAPPENS FOR EXAMPLE IF SOMEONE HANDS YOU A CUSTOM TAG LIBRARY THEY CREATED FOR YOUR COMPANY OR PROJECT (OW DO YOU KNOW WHAT THE TAGS ARE AND HOW TO USE THEM 7ITH *34, IT S EASYÂ&#x2C6;THE *34, SPECIlCATION DOCUMENTS EACH TAG INCLUDING HOW TO USE EACH OF THE REQUIRED AND OPTIONAL ATTRIBUTES "UT NOT EVERY CUSTOM TAG WILL COME SO NICELY PACKAGED AND WELL DOCUMENTED 9OU HAVE TO KNOW HOW TO lGURE OUT A TAG EVEN IF THE DOCUMENTATION IS WEAK OR NONEXISTENT AND ONE MORE THINGÂ&#x2C6;YOU HAVE TO KNOW HOW TO DEPLOY A CUSTOM TAG LIBRARY

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7KH WDJ QDPH DQG V\QWD[ 4HE TAG HAS A NAME OBVIOUSLY )N C SET THE TAG NAME IS SET AND THE PRElX IS C 9OU CAN USE ANY PRElX YOU WANT BUT THE NAME COMES FROM THE 4,$ 4HE SYNTAX INCLUDES THINGS LIKE REQUIRED AND OPTIONAL ATTRIBUTES WHETHER THE TAG CAN HAVE A BODY AND IF SO WHAT YOU CAN PUT THERE THE TYPE OF EACH ATTRIBUTE AND WHETHER THE ATTRIBUTE CAN BE AN EXPRESSION VS A LITERAL 3TRING

7KH OLEUDU\ 85, 4HE 52) IS A UNIQUE IDENTIlER IN THE 4AG ,IBRARY $ESCRIPTOR 4,$ )N OTHER WORDS IT S A UNIQUE NAME FOR THE TAG LIBRARY THE 4,$ DESCRIBES 4HE 52) IS WHAT YOU PUT IN YOUR TAGLIB DIRECTIVE )T S WHAT TELLS THE #ONTAINER HOW TO IDENTIFY THE 4,$ lLE WITHIN THE WEB APP WHICH THE #ONTAINER NEEDS IN ORDER TO MAP THE TAG NAME USED IN THE *30 TO THE *AVA CODE THAT RUNS WHEN YOU USE THE TAG

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Chapter 9. Custom tags are powerful

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5ISQVO [MV[M WN \PM <4, 4HE 4,$ DESCRIBES TWO MAIN THINGS CUSTOM TAGS AND %, FUNCTIONS 7E USED ONE WHEN WE MADE THE DICE ROLLING FUNCTION IN THE PREVIOUS CHAPTER BUT WE HAD ONLY A FUNCTION ELEMENT IN THE 4,$ .OW WE HAVE TO LOOK AT THE TAG ELEMENT WHICH CAN BE MORE COMPLEX "ESIDES THE FUNCTION WE DECLARED EARLIER THE $$ BELOW DESCRIBES ONE TAG ADVICE

schema that the XML orize it... of n io rs em ve m This is ther JSP 2.0. DonĂ&#x2022;tlib> element. you use fo it into your <tag just copy

value)Ă&#x2018; he tag, not the rary. MANDATORY (tclare the version of the tag lib de to in it puts

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Chapter 9. Custom tags are powerful

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=[QVO \PM K][\WU ÂšIL^QKMÂş \IO 4HE hADVICEv TAG IS A SIMPLE TAG THAT TAKES ONE ATTRIBUTEÂ&#x2C6;THE USER NAMEÂ&#x2C6;AND PRINTS OUT A PIECE OF RANDOM ADVICE )T S SIMPLE ENOUGH THAT IT COULD HAVE BEEN JUST A PLAIN OLD %, FUNCTION WITH A STATIC METHOD GET!DVICE 3TRING NAME BUT WE MADE IT A SIMPLE TAG TO SHOW YOU HOW IT ALL WORKS

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uri> ches the < The uri minatthe TLD. element

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ue> ItĂ&#x2022;s OK to use EL here, because the <rtexpreval ute. in the TLD is set to Ă&#x2019;trueĂ&#x201C; for the user attrib (Assume the Ă&#x2019;userNameĂ&#x201C; attribute already exists.)

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Each library yo needs its own taugliuse in a page with a unique preĂ&#x17E; b directive x.

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Chapter 9. Custom tags are powerful

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<PM K][\WU \IO PIVLTMZ 4HIS SIMPLE TAG HANDLER EXTENDS 3IMPLE4AG3UPPORT A CLASS YOU LL SEE IN THE NEXT CHAPTER AND IMPLEMENTS TWO KEY METHODS DO4AG THE METHOD THAT DOES THE ACTUAL WORK AND SET5SER THE METHOD THAT ACCEPTS THE ATTRIBUTE VALUE

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The Container lls this method to set the tag attribuca the value conventions to Ă&#x17E;tegu. It uses JavaBean property namifrom re ou t th at a serĂ&#x201C; attribu ng should be sent to te the setUser() meĂ&#x2019;uth od.

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Chapter 9. Custom tags are powerful

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8Ia I\\MV\QWV \W $Z\M`XZ ^IT]M& 4HE RTEXPRVALUE IS ESPECIALLY IMPORTANT BECAUSE IT TELLS YOU WHETHER THE VALUE OF THE ATTRIBUTE IS EVALUATED AT TRANSLATION OR RUNTIME )F THE RTEXPRVALUE IS FALSE OR THE RTEXPRVALUE ISN T DEl NED YOU CAN USE ONLY A 3TRING LITERAL AS THAT ATTRIBUTE S VALUE ,I \RX VHH WKLV DWWULEXWH! QDPH!UDWH QDPH! UHTXLUHG!WUXH UHTXLUHG! UWH[SUYDOXH!IDOVH UWH[SUYDOXH! DWWULEXWH!

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be an NO ! This must NOstT be a mu it .. on. ssi expre String literal.

9OU STILL DIDN T ANSWER THE QUESTION ABOUT HOW YOU KNOW WHAT TYPE THE ATTRIBUTE IS

7E LL START WITH THE EASY ONE )F THE RTEXPRVALUE IS FALSE OR NOT THERE AT ALL THEN THE ATTRIBUTE TYPE CAN BE /.,9 A 3TRING LITERAL "UT IF YOU CAN USE AN EXPRESSION THEN YOU HAVE TO HOPE THAT IT S EITHER DEAD OBVIOUS FROM THE TAG DESCRIPTION AND ATTRIBUTE NAME /2 THAT THE DEVELOPER INCLUDED THE OPTIONAL TYPE SUBELEMENT OF THE ATTRIBUTE ELEMENT 4HE TYPE TAKES A FULLY QUALIFIED CLASS NAME FOR THE TYPE 7HETHER THE 4,$ DECLARES THE TYPE OR NOT THE #ONTAINER EXPECTS THE TYPE OF THE EXPRESSION TO MATCH THE TYPE OF ARGUMENT IN THE TAG HANDLER S SETTER METHOD FOR THAT ATTRIBUTE )N OTHER WORDS IF THE TAG HANDLER HAS A SET$OG $OG METHOD FOR THE hDOGv ATTRIBUTE THEN THE VALUE OF YOUR EXPRESSION FOR THAT ATTRIBUTE BETTER EVALUATE TO A $OG OBJECT /R SOMETHING THAT CAN BE IMPLICITLY ASSIGNED TO A $OG REFERENCE TYPE

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Chapter 9. Custom tags are powerful

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$Z\M`XZ ^IT]M& Q[ 67< R][\ NWZ -4 M`XZM[[QWV[ 9OU CAN USE THREE KINDS OF EXPRESSIONS FOR THE VALUE OF AN ATTRIBUTE OR TAG BODY THAT ALLOWS RUNTIME EXPRESSIONS

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6FULSWLQJ H[SUHVVLRQV PLQH DGYLFH XVHU Âś UHTXHVW JHW$WWULEXWH ÂłXVHUQDPHÂ´ Âś ! !

It has to be an expression, not just a scriplet. So it must have the Ă&#x2019;=Ă&#x201C; sign in there and no semicolon on the end.

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What is this?? I thought this tag didnĂ&#x2022;t have a body...

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Chapter 9. Custom tags are powerful

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?PI\ KIV JM QV I \IO JWLa ! TAG CAN HAVE A BODY ONLY IF THE BODY CONTENT ELEMENT FOR THIS TAG IS NOT CONlGURED WITH A VALUE OF EMPTY 4HE BODY CONTENT ELEMENT CAN BE ONE OF EITHER THREE OR FOUR VALUES DEPENDING ON THE TYPE OF TAG ERG\ FRQWHQW!HPSW\ ERG\ FRQWHQW!

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s, ts (scriptletha ve ripting elemenbu sc N ve CA ha it T t NO The tag mustpressions, and declarations),d standard actions. scripting ex and EL and custom an template text

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T have a body

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The tag body is treated as plain text, so the EL is NOT evaluated and tags/actions are not triggered.

The tag body can have anything that can go inside a JSP.

7+5(( ZD\V WR LQYRNH D WDJ WKDW FDQÂˇW KDYH D ERG\ %ACH OF THESE ARE ACCEPTABLE WAYS TO INVOKE A TAG CONlGURED IN THE 4,$ WITH BODY CONTENT EMPTY BODY CONTENT

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slash u put a When yoopening tag, youg. in the se a closing ta donĂ&#x2022;t u

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We have an tag, but NOTopening and closing HING in betwee n.

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The <jsp:attribute> tag is the ONLY thing the opening and closing tags of a tag with you can put between a <body-content> of empty! ItĂ&#x2022;s just an alternate way to put <jsp:attribute> tags donĂ&#x2022;t count as Ă&#x2019;bodythe attributes in, but contentĂ&#x201C;.

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Chapter 9. Custom tags are powerful

XVLQJ -67/

<PM \IO PIVLTMZ \PM <4, IVL \PM 2;8 These three handler class,piecesĂ&#x2018;the tag the JSP are the TLD, and all you need to deploy and ru that uses the n a web app tag.

4HE TAG HANDLER DEVELOPER CREATES THE 4,$ TO TELL BOTH THE #ONTAINER AND THE *30 DEVELOPER HOW TO USE THE TAG ! *30 DEVELOPER DOESN T CARE ABOUT THE TAG CLASS ELEMENT IN THE 4,$ THAT S FOR THE #ONTAINER TO WORRY ABOUT 4HE *30 DEVELOPER CARES MOST ABOUT THE URI THE TAG NAME AND THE TAG SYNTAX #AN THE TAG HAVE A BODY $OES THIS ATTRIBUTE HAVE TO BE A 3TRING LITERAL OR CAN IT BE AN EXPRESSION )S THIS ATTRIBUTE OPTIONAL 7HAT TYPE DOES THE EXPRESSION NEED TO EVALUATE TO 4HINK OF THE 4,$ AS THE !0) FOR CUSTOM TAGS 9OU HAVE TO KNOW HOW TO CALL IT AND WHAT ARGUMENTS IT NEEDS

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Chapter 9. Custom tags are powerful

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<PM \IOTQJ $]ZQ& Q[ R][\ I VIUM VW\ I TWKI\QWV 4HE URI ELEMENT IN THE 4,$ IS A UNIQUE NAME FOR THE TAG LIBRARY 4HAT S IT )T DOES ./4 NEED TO REPRESENT ANY ACTUAL LOCATION PATH OR 52, FOR EXAMPLE )T SIMPLY HAS TO BE A NAMEÂ&#x2C6;THE SAME NAME YOU USE IN THE TAGLIB DIRECTIVE h"UT v YOU RE ASKING hHOW COME WITH THE *34, IT GIVES THE FULL 52, TO THE LIBRARY v 4HE TAGLIB DIRECTIVE FOR THE *34, IS # WDJOLE SUHÂż[ Â´FÂ´ XUL Â´KWWS MDYD VXQ FRP MVS MVWO FRUHÂ´ !

4HE WEB #ONTAINER DOESN T NORMALLY TRY TO REQUEST SOMETHING FROM THE URI IN THE TAGLIB DIRECTIVE )T DOESN T NEED TO USE THE URI AS A LOCATION )F YOU TYPE THAT AS A 52, INTO YOUR BROWSER YOU LL BE REDIRECTED TO A DIFFERENT 52, ONE THAT HAS INFORMATION ABOUT *34, 4HE #ONTAINER COULD CARE LESS THAT THIS PARTICULAR URI HAPPENS TO ALSO BE A VALID 52, THE WHOLE hHTTP v THING )T S JUST THE CONVENTION 3UN USES FOR THE URI TO HELP ENSURE THAT IT S A UNIQUE NAME 3UN COULD HAVE NAMED THE *34, URI hJAVA?FOO?TAGSv AND IT WOULD HAVE WORKED IN EXACTLY THE SAME WAY !LL THAT MATTERS IS THAT THE URI IN THE 4,$ AND THE URI IN THE TAGLIB DIRECTIVE MATCH

URL to This LOOKS likebuat itĂ&#x2022;s not. , rce ou res b we a happens ItĂ&#x2022;s just a name thasata URL. d te at rm fo to be

!S A DEVELOPER THOUGH YOU DO WANT TO WORK OUT A SCHEME TO GIVE YOUR LIBRARIES UNIQUE URI VALUES BECAUSE URI NAMES NEED TO BE UNIQUE FOR ANY GIVEN WEB APP 9OU CAN T FOR EXAMPLE HAVE TWO 4,$ lLES IN THE SAME WEB APP WITH THE SAME URI 3O THE DOMAIN NAME CONVENTION IS A GOOD ONE BUT YOU DON T NECESSARILY NEED TO USE THAT FOR ALL OF YOUR IN HOUSE DEVELOPMENT (AVING SAID ALL THAT THERE IS ONE WAY IN WHICH THE URI COULD BE USED AS A LOCATION BUT IT S CONSIDERED A REALLY BAD PRACTICEÂ&#x2C6;IF YOU DON T SPECIFY A URI INSIDE THE 4,$ THE #ONTAINER WILL ATTEMPT TO USE THE URI ATTRIBUTE IN THE TAGLIB DIRECTIVE AS A PATH TO THE ACTUAL 4,$ "UT TO HARD CODE THE LOCATION OF YOUR 4,$ IS OBVIOUSLY A BAD IDEA SO JUST PRETEND YOU DON T KNOW IT S POSSIBLE

V IRU D PDWFK N R R O HU LQ WD Q R & 7KH LQ WKH 7/' DQG L! XU KH W Q HH Z HW E E GLUHFWLYH OL DJ W KH W LQ H OX YD WKH XUL DYH WR EH WKH K 7 2 1 HV R G UL X 7KH WXDO WDJ KDQGOHU DF H WK I R Q R WL FD OR

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Chapter 9. Custom tags are powerful

XVLQJ -67/

<PM +WV\IQVMZ J]QTL[ I UIX "EFORE *30 THE DEVELOPER HAD TO SPECIFY A MAPPING BETWEEN THE URI IN THE 4,$ AND THE ACTUAL LOCATION OF THE 4,$ lLE 3O WHEN A *30 PAGE HAD A TAGLIB DIRECTIVE LIKE THIS # WDJOLE SUHÂż[ Â´PLQHÂ´ XUL Â´UDQGRP7KLQJVÂ´ ! 4HE $EPLOYMENT $ESCRIPTOR WEB XML HAD TO TELL THE #ONTAINER WHERE THE 4,$ lLE WITH A MATCHING URI WAS LOCATED 9OU DID THAT WITH A TAGLIB ELEMENT IN THE $$

7KH 2/' EHIRUH -63 ZD\ WR PDS D WDJOLE XUL WR D 7/' Ă&#x20AC;OH ZHE DSS! MVS FRQÂżJ! WDJOLE! WDJOLE XUL!UDQGRP7KLQJV WDJOLE XUL! WDJOLE ORFDWLRQ! :(% ,1) P\)XQFWLRQV WOG WDJOLE ORFDWLRQ! WDJOLE! MVS FRQÂżJ! ZHE DSS!

ap the <uri> In the DD, mto an actual D L T in the D Ă&#x17E;le. path to a TL

7KH 1(: -63 ZD\ WR PDS D WDJOLE XUL WR D 7/' Ă&#x20AC;OH

1R WDJOLE! HQWU\ LQ WKH '' 4HE #ONTAINER AUTOMATICALLY BUILDS A MAP BETWEEN 4,$ lLES AND URI NAMES SO THAT WHEN A *30 INVOKES A TAG THE #ONTAINER KNOWS EXACTLY WHERE TO lND THE 4,$ THAT DESCRIBES THE TAG (OW "Y LOOKING THROUGH A SPECIlC SET OF LOCATIONS WHERE 4,$S ARE ALLOWED TO LIVE 7HEN YOU DEPLOY A WEB APP AS LONG AS YOU PUT THE 4,$ IN A PLACE THE #ONTAINER WILL SEARCH THE #ONTAINER WILL lND THE 4,$ AND BUILD A MAP FOR THAT TAG LIBRARY )F YOU DO SPECIFY AN EXPLICIT TAGLIB LOCATION IN THE $$ WEB XML A *30 #ONTAINER WILL USE IT )N FACT WHEN THE #ONTAINER BEGINS TO BUILD THE URI TO 4,$ MAP THE #ONTAINER WILL LOOK lRST IN YOUR $$ TO SEE IF YOU VE MADE ANY TAGLIB ENTRIES AND IF YOU HAVE IT LL USE THOSE TO HELP CONSTRUCT THE MAP &OR THE EXAM YOU RE EXPECTED TO KNOW ABOUT TAGLIB LOCATION EVEN THOUGH IT S NO LONGER REQUIRED FOR *30 3O THE NEXT STEP IS FOR US TO SEE WHERE THE #ONTAINER LOOKS FOR 4,$S AND ALSO WHERE IT LOOKS FOR THE TAG HANDLER CLASSES DECLARED IN THE 4,$S

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Chapter 9. Custom tags are powerful

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.W]Z XTIKM[ \PM +WV\IQVMZ TWWS[ NWZ <4,[ 4HE #ONTAINER SEARCHES IN SEVERAL PLACES TO l ND 4,$ l LESÂ&#x2C6;YOU DON T NEED TO DO ANYTHING EXCEPT MAKE SURE YOUR 4,$S ARE IN ONE OF THE RIGHT LOCATIONS

The JSP that invokes the tag

'LUHFWO\ LQVLGH :(% ,1)

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Chapter 9. Custom tags are powerful

XVLQJ -67/

?PMV I 2;8 ][M[ UWZM \PIV WVM \IO TQJZIZa )F YOU WANT TO USE MORE THAN ONE TAG LIBRARY IN A *30 DO A SEPARATE TAGLIB DIRECTIVE FOR EACH 4,$ 4HERE A FEW ISSUES TO KEEP IN MIND

-AKE SURE THE TAGLIB URI NAMES ARE UNIQUE )N OTHER WORDS DON T PUT IN MORE THAN ONE DIRECTIVE WITH THE SAME URI VALUE

$O ./4 USE A PRElX THAT S ON THE RESERVED LIST 4HE RESERVED PRElXES ARE MVS

MVS[

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MDYD[

VHUYOHW

VXQ

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6KDUSHQ \RXU SHQFLO (PSW\ WDJV

:ULWH LQ H[DPSOHV RI WKH 7+5(( GLIIHUHQW ZD\V WR LQYRNH D WDJ WKDW PXVW KDYH DQ HPSW\ ERG\ &KHFN \RXU DQVZHUV E\ ORRNLQJ EDFN WKURXJK WKH FKDSWHU 1R ZHÂ·UH QRW JRLQJ WR WHOO \RX WKH SDJH QXPEHU

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Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful

XVLQJ -67/

6KDUSHQ \RXU SHQFLO

7HVW \RXU 7DJ PHPRU\ $16:(56

The attribute that names the loop counter variable.

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value, but you The <c:set> tag must havevaluae in the body could choose to put the an attribute. of the tag instead of as

value Â´IRRÂ´ ! F VHW YDU Â´XVHU/HYHOÂ´ VFRSH Â´VHVVLRQÂ´

)LOO LQ WKH PLVVLQJ WDJ QDPHV WZR GLIIHUHQW WDJ W\SHV DQG WKH PLVVLQJ DWWULEXWH QDPH F FKRRVH! F when test Â´ ^XVHU3UHI ÂľSHUIRUPDQFHÂś`Â´! 1RZ \RX FDQ VWRS HYHQ LI \RX HP!GR HP! GULYH LQVDQHO\ IDVW F ! when F ! otherwise 2XU EUDNHV DUH WKH EHVW F ! otherwise F FKRRVH!

l. The <c:otherwise> tag is optiona \RX DUH KHUH

Chapter 9. Custom tags are powerful

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Chapter 9. Custom tags are powerful

XVLQJ -67/

0RFN ([DP &KDSWHU

7HICH IS TRUE ABOUT 4,$ lLES

R ! 4,$ lLES MAY BE PLACED IN ANY SUBDIRECTORY OF :(% ,1) R " 4,$ lLES ARE USED TO CONlGURE *30 ENVIRONMENT ATTRIBUTES SUCH AS VFULSWLQJ LQYDOLG

R # 4,$ lLES MAY BE PLACED IN THE 0(7$ ,1) DIRECTORY OF THE 7!2 lLE

R $ 4,$ lLES CAN DECLARE BOTH 3IMPLE AND #LASSIC TAGS BUT 4,$ lLES ARE ./4 USED TO DECLARE 4AG &ILES

!SSUMING THE STANDARD *34, PRElX CONVENTIONS ARE USED WHICH *34, TAGS WOULD YOU USE TO ITERATE OVER A COLLECTION OF OBJECTS #HOOSE ALL THAT APPLY

R ! [ IRU(DFK! R " F LWHUDWH! R # F IRU(DFK! R $ F IRU7RNHQV! R % ORJLF LWHUDWH! R & ORJLF IRU(DFK!

\RX DUH KHUH

Chapter 9. Custom tags are powerful

PRFN H[DP

! *30 PAGE CONTAINS A WDJOLE DIRECTIVE WHOSE XUL ATTRIBUTE HAS THE VALUE P\7DJV 7HICH DEPLOYMENT DESCRIPTOR ELEMENT DElNES THE ASSOCIATED 4,$

R ! WDJOLE! XUL!P\7DJV XUL! ORFDWLRQ! :(% ,1) P\7DJV WOG ORFDWLRQ! WDJOLE!

R " WDJOLE! XUL!P\7DJV XUL! WOG ORFDWLRQ! :(% ,1) P\7DJV WOG WOG ORFDWLRQ! WDJOLE!

R # WDJOLE! WOG XUL!P\7DJV WOG XUL! WOG ORFDWLRQ! :(% ,1) P\7DJV WOG WOG ORFDWLRQ! WDJOLE!

R $ WDJOLE! WDJOLE XUL!P\7DJV WDJOLE XUL! WDJOLE ORFDWLRQ! :(% ,1) P\7DJV WOG WDJOLE ORFDWLRQ! WDJOLE!

! *AVA"EAN 3HUVRQ HAS A PROPERTY CALLED DGGUHVV 4HE VALUE OF THIS PROPERTY IS ANOTHER *AVA"EAN $GGUHVV WITH THE FOLLOWING STRING PROPERTIES VWUHHW VWUHHW FLW\ VWDWH&RGH AND ]LS&RGH ! CONTROLLER SERVLET CREATES A SESSION SCOPED ATTRIBUTE CALLED FXVWRPHU THAT IS AN INSTANCE OF THE 3HUVRQ BEAN 7HICH *30 CODE STRUCTURES WILL SET THE FLW\ PROPERTY OF THE FXVWRPHU ATTRIBUTE TO THE FLW\ REQUEST PARAMETER #HOOSE ALL THAT APPLY

R ! ^VHVVLRQ6FRSH FXVWRPHU DGGUHVV FLW\ SDUDP FLW\` R " F VHW WDUJHW Â´ ^VHVVLRQ6FRSH FXVWRPHU DGGUHVV`Â´ SURSHUW\ Â´FLW\Â´ YDOXH Â´ ^SDUDP FLW\`Â´ !

R # F VHW VFRSH Â´VHVVLRQÂ´ YDU Â´ ^FXVWRPHU DGGUHVV`Â´ SURSHUW\ Â´FLW\Â´ YDOXH Â´ ^SDUDP FLW\`Â´ !

R $ F VHW WDUJHW Â´ ^VHVVLRQ6FRSH FXVWRPHU DGGUHVV`Â´ SURSHUW\ Â´FLW\Â´! ^SDUDP FLW\` F VHW!

FKDSWHU

Chapter 9. Custom tags are powerful

XVLQJ -67/

7HICH ERG\ FRQWHQW! ELEMENT COMBINATIONS IN THE 4,$ ARE VALID FOR THE FOLLOWING *30 SNIPPET #HOOSE ALL THAT APPLY P\ WDJ ! P\ WDJ D Â´ Â´ ! D ! P\ WDJ ! YDOXH ^D` P\ WDJ ! P\ WDJ !

R ! TAG BODY CONTENT IS HPSW\ TAG BODY CONTENT IS -63 TAG BODY CONTENT IS VFULSWOHVV

R " TAG BODY CONTENT IS -63 TAG BODY CONTENT IS HPSW\ TAG BODY CONTENT IS VFULSWOHVV

R # TAG BODY CONTENT IS -63 TAG BODY CONTENT IS -63 TAG BODY CONTENT IS -63

R $ TAG BODY CONTENT IS VFULSWOHVV TAG BODY CONTENT IS -63 TAG BODY CONTENT IS -63

R % TAG BODY CONTENT IS -63 TAG BODY CONTENT IS VFULSWOHVV TAG BODY CONTENT IS VFULSWOHVV

!SSUMING THE APPROPRIATE WDJOLE DIRECTIVES WHICH ARE VALID EXAMPLES OF CUSTOM TAG USAGE #HOOSE ALL THAT APPLY

R ! IRR EDU ! R " P\ WDJ! P\ WDJ! R # P\WDJ YDOXH Â´[Â´ ! R $ F RXW YDOXH Â´[Â´ ! R % MVS VHW3URSHUW\ QDPH Â´DÂ´ SURSHUW\ Â´EÂ´ YDOXH Â´FÂ´ !

\RX DUH KHUH

Chapter 9. Custom tags are powerful

PRFN H[DP

'IVEN THE FOLLOWING SCRIPTLET CODE VHOHFW QDPH Â¶VW\OH,GÂ¶! %HHU6W\OHV>@ VW\OHV EHHU6HUYLFH JHW6W\OHV IRU LQW L L VW\OHV OHQJWK L ^ %HHU6W\OH VW\OH VW\OHV>L@ ! RSWLRQ YDOXH Â¶ VW\OH JHW2EMHFW,' !Â¶! VW\OH JHW7LWOH ! RSWLRQ! ` ! VHOHFW! 7HICH *34, CODE SNIPPET PRODUCES THE SAME RESULT

R ! VHOHFW QDPH Â¶VW\OH,GÂ¶! F IRU DUUD\ Â¶ ^EHHU6HUYLFH VW\OHV`Â¶! RSWLRQ YDOXH Â¶ ^LWHP REMHFW,'`Â¶! ^LWHP WLWOH` RSWLRQ! F IRU! VHOHFW! R " VHOHFW QDPH Â¶VW\OH,GÂ¶! F IRU(DFK YDU Â¶VW\OHÂ¶ LWHPV Â¶ ^EHHU6HUYLFH VW\OHV`Â¶! RSWLRQ YDOXH Â¶ ^VW\OH REMHFW,'`Â¶! ^VW\OH WLWOH` RSWLRQ! F IRU(DFK! VHOHFW!

R # VHOHFW QDPH Â¶VW\OH,GÂ¶! F IRU YDU Â¶VW\OHÂ¶ DUUD\ Â¶ ^EHHU6HUYLFH VW\OHV`Â¶! RSWLRQ YDOXH Â¶ ^VW\OH REMHFW,'`Â¶! ^VW\OH WLWOH` RSWLRQ! F IRU! VHOHFW!

R $ VHOHFW QDPH Â¶VW\OH,GÂ¶! F IRU(DFK YDU Â¶VW\OHÂ¶ DUUD\ Â¶ ^EHHU6HUYLFH VW\OHV`Â¶! RSWLRQ YDOXH Â¶ ^VW\OH REMHFW,'`Â¶! ^VW\OH WLWOH` RSWLRQ! F IRU! VHOHFW!

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Chapter 9. Custom tags are powerful

XVLQJ -67/

&KDSWHU $QVZHUV

(JSP v2.01-160) pgs 3-16,

7HICH IS TRUE ABOUT 4,$ lLES

R ! 4,$ lLES MAY BE PLACED IN ANY SUBDIRECTORY OF :(% ,1)

-Option B is invalid because TLD the JSP environment.

R " 4,$ lLES ARE USED TO CONlGURE *30 ENVIRONMENT ATTRIBUTES Ă&#x17E;les conĂ&#x17E;gure tag handlers not SUCH AS VFULSWLQJ LQYDOLG

-Option C is invalid because TLD Ă&#x17E;les are not recognized in the META-INF of the WAR Ă&#x17E;le.

R # 4,$ lLES MAY BE PLACED IN THE 0(7$ ,1) DIRECTORY OF THE 7!2 lLE

R $ 4,$ lLES CAN DECLARE BOTH 3IMPLE AND #LASSIC TAGS BUT 4,$ -Option D is invalid because lLES ARE ./4 USED TO DECLARE 4AG &ILES

Tag Files may be declared in a TLD (but it is rare).

!SSUMING THE STANDARD *34, PRElX CONVENTIONS ARE USED WHICH *34, TAGS WOULD YOU USE TO ITERATE OVER A COLLECTION OF OBJECTS #HOOSE ALL THAT APPLY

R ! [ IRU(DFK! R " F LWHUDWH!

(JSTL v1.1 pg. 4

-Option A is incorrect as this is the tag used for iterating over XPath expressions.

-Option B is incorrect because no such tag exists.

R # F IRU(DFK! R $ F IRU7RNHQV! R % ORJLF LWHUDWH! R & ORJLF IRU(DFK!

-Option D is incorrect because this tag is used for iterating over tokens within a single string.

-Options E and F are incorrect because the preĂ&#x17E;x Ă&#x201D;logicĂ&#x2022; is not a standard JSTL preĂ&#x17E;x (this preĂ&#x17E;x is typically used by tags in the Jakarta Struts package). \RX DUH KHUH

Chapter 9. Custom tags are powerful

PRFN DQVZHUV

12,13) (JSP v2.0 pgs 3-

! *30 PAGE CONTAINS A WDJOLE DIRECTIVE WHOSE XUL ATTRIBUTE HAS THE VALUE P\7DJV 7HICH DEPLOYMENT DESCRIPTOR ELEMENT DElNES THE ASSOCIATED 4,$

R ! WDJOLE! XUL!P\7DJV XUL! ORFDWLRQ! :(% ,1) P\7DJV WOG ORFDWLRQ! WDJOLE!

R " WDJOLE! XUL!P\7DJV XUL! WOG ORFDWLRQ! :(% ,1) P\7DJV WOG WOG ORFDWLRQ! WDJOLE!

R # WDJOLE! WOG XUL!P\7DJV WOG XUL! WOG ORFDWLRQ! :(% ,1) P\7DJV WOG WOG ORFDWLRQ! WDJOLE!

R $ WDJOLE!

- Option D speciĂ&#x17E;es elements.

valid tag WDJOLE XUL!P\7DJV WDJOLE XUL! WDJOLE ORFDWLRQ! :(% ,1) P\7DJV WOG WDJOLE ORFDWLRQ! WDJOLE!

-28)

(JSTL v1.1 pg 4

7HICH *30 CODE STRUCTURES WILL SET THE FLW\ PROPERTY OF THE FXVWRPHU ATTRIBUTE TO THE FLW\ REQUEST PARAMETER #HOOSE ALL THAT APPLY

R ! ^VHVVLRQ6FRSH FXVWRPHU DGGUHVV FLW\ SDUDP FLW\` R " F VHW WDUJHW Â´ ^VHVVLRQ6FRSH FXVWRPHU DGGUHVV`Â´

-Option A is invalid because EL does not permit assignment.

SURSHUW\ Â´FLW\Â´ YDOXH Â´ ^SDUDP FLW\`Â´ !

R # F VHW VFRSH Â´VHVVLRQÂ´ YDU Â´ ^FXVWRPHU DGGUHVV`Â´ SURSHUW\ Â´FLW\Â´ YDOXH Â´ ^SDUDP FLW\`Â´ !

R $ F VHW WDUJHW Â´ ^VHVVLRQ6FRSH FXVWRPHU DGGUHVV`Â´ SURSHUW\ Â´FLW\Â´! ^SDUDP FLW\` F VHW!

-Option C is invalid because the var attribute does not accept a runtime value, nor does it work with the property attribute.

FKDSWHU

Chapter 9. Custom tags are powerful

XVLQJ -67/

7HICH ERG\ FRQWHQW! ELEMENT COMBINATIONS IN THE 4,$ ARE VALID FOR THE FOLLOWING *30 SNIPPET #HOOSE ALL THAT APPLY P\ WDJ ! P\ WDJ D Â´ Â´ ! D ! P\ WDJ ! YDOXH ^D` P\ WDJ ! P\ WDJ !

pendix JSP.C3-30) (JSP v2.0 Ap 21 and s pg speciĂ&#x17E;cally 3-

so it must have at -Tag1 includes scripting code only shown least Ă&#x201D;JSPĂ&#x2022; body-content. Tag2alsois cont Ă&#x201D;JSPĂ&#x2022; as an empty tag, but it could. Tag3 containains no tent -con body Ă&#x2022; tless or Ă&#x201D;scrip Ă&#x2022; or scripting code so it may have either Ă&#x201D;JSP . tent -con body Ă&#x2022; tless Ă&#x201D;scrip

R ! TAG BODY CONTENT IS HPSW\ TAG BODY CONTENT IS -63 TAG BODY CONTENT IS VFULSWOHVV

-Option A is invalid because tag1 cannot be Ă&#x201D;emptyĂ&#x2022;.

R " TAG BODY CONTENT IS -63 TAG BODY CONTENT IS HPSW\ TAG BODY CONTENT IS VFULSWOHVV

R # TAG BODY CONTENT IS -63 TAG BODY CONTENT IS -63 TAG BODY CONTENT IS -63

R $ TAG BODY CONTENT IS VFULSWOHVV TAG BODY CONTENT IS -63 TAG BODY CONTENT IS -63

-Option D is invalid because tag1 cannot be Ă&#x201D;scriptlessĂ&#x2022;.

R % TAG BODY CONTENT IS -63 TAG BODY CONTENT IS VFULSWOHVV TAG BODY CONTENT IS VFULSWOHVV

!SSUMING THE APPROPRIATE WDJOLE DIRECTIVES WHICH ARE VALID EXAMPLES OF CUSTOM TAG USAGE #HOOSE ALL THAT APPLY

(JSP v2.0 section

R ! IRR EDU ! R " P\ WDJ! P\ WDJ! -Option C is invalid because R # P\WDJ YDOXH Â´[Â´ ! there is no preĂ&#x17E;x. R $ F RXW YDOXH Â´[Â´ ! R % MVS VHW3URSHUW\ QDPH Â´DÂ´ SURSHUW\ Â´EÂ´ YDOXH Â´FÂ´ !

-Option E is invalid because this is an example of a JSP standard action, not a custom tag. \RX DUH KHUH

Chapter 9. Custom tags are powerful

PRFN DQVZHUV

48)

(JSTL v1.1 pg 6-

7HICH *34, CODE SNIPPET PRODUCES THE SAME RESULT

R ! VHOHFW QDPH Â¶VW\OH,GÂ¶! F IRU DUUD\ Â¶ ^EHHU6HUYLFH VW\OHV`Â¶! RSWLRQ YDOXH Â¶ ^LWHP REMHFW,'`Â¶! ^LWHP WLWOH` RSWLRQ! F IRU! VHOHFW! -Option B is correct because R " VHOHFW QDPH Â¶VW\OH,GÂ¶!

it uses the proper JSTL tag/attribute names.

F IRU(DFK YDU Â¶VW\OHÂ¶ LWHPV Â¶ ^EHHU6HUYLFH VW\OHV`Â¶! RSWLRQ YDOXH Â¶ ^VW\OH REMHFW,'`Â¶! ^VW\OH WLWOH` RSWLRQ! F IRU(DFK! VHOHFW!

R # VHOHFW QDPH Â¶VW\OH,GÂ¶! F IRU YDU Â¶VW\OHÂ¶ DUUD\ Â¶ ^EHHU6HUYLFH VW\OHV`Â¶! RSWLRQ YDOXH Â¶ ^VW\OH REMHFW,'`Â¶! ^VW\OH WLWOH` RSWLRQ! F IRU! VHOHFW!

R $ VHOHFW QDPH Â¶VW\OH,GÂ¶! F IRU(DFK YDU Â¶VW\OHÂ¶ DUUD\ Â¶ ^EHHU6HUYLFH VW\OHV`Â¶! RSWLRQ YDOXH Â¶ ^VW\OH REMHFW,'`Â¶! ^VW\OH WLWOH` RSWLRQ! F IRU! VHOHFW!

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Chapter 10. When even JSTL is not enough...

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Chapter 10. When even JSTL is not enough... Head First Servlets and JSP By Bert Bates, Kathy Sierra, Bryan Basham ISBN: 0596005407 Publisher:Prepared for Augusto Jaramillo Forcada, Safari ID: augustojf.cv@gmail.com O'Reilly Print Publication Date: 8/1/2004 User number: 729515 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited.

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$OES THE 4AG &ILE HAVE ACCESS TO THE REQUEST AND RESPONSE IMPLICIT OBJECTS

4,$ ENTRIES FOR A 4AG &ILE DESCRIBE ONLY THE LOCATION OF THE ACTUAL 4AG &ILE 4HE 4,$ FOR A 4AG &ILE LOOKS LIKE THIS

9ES 2EMEMBER EVEN THOUGH IT S A TAG FILE IT S GONNA END UP AS PART OF A *30 9OU CAN USE THE IMPLICIT REQUEST AND RESPONSE OBJECTS IF YOU DO SCRIPTING THE NORMAL %, IMPLICIT OBJECTS ARE ALWAYS THERE AS WELL AND YOU HAVE ACCESS TO A *SP#ONTEXT AS WELL 9OU DON T HAVE A 3ERVLET#ONTEXT THOUGHÂ&#x2C6;A 4AG &ILE USES A *SP#ONTEXT INSTEAD OF A 3ERVLET#ONTEXT

TAGLIB TLIB VERSION TLIB VERSION URI MY4AG,IBRARY URI TAG FILE NAME (EADER NAME PATH -%4! ).& TAGS (EADER TAG PATH TAG FILE

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) THOUGHT ON THE OPPOSITE PAGE YOU JUST SAID WE COULD NOT DO SCRIPTING IN A 4AG &ILE

.O THAT S NOT EXACTLY WHAT WE SAID 9OU CAN DO SCRIPTING IN A 4AG &ILE BUT YOU CAN T DO SCRIPTING INSIDE THE BODY OF THE TAG USED TO INVOKE THE 4AG &ILE

#AN YOU COMBINE 4AG &ILES AND 4,$S FOR CUSTOM TAGS IN THE SAME DIRECTORY

.OTICE THAT DECLARING A TAG FILE IS QUITE DIFFERENT FROM DECLARING AN ACTUAL TAG

7HY DID THEY DO IT THIS WAY 7OULDN T IT BE SO MUCH SIMPLER TO JUST HAVE CUSTOM TAGS AND 4AG &ILES DECLARED THE SAME WAY IN A 4,$ "UT ./ INSTEAD THEY HAD TO COME UP WITH THIS WHOLE OTHER THING WHERE YOU HAVE TO USE NEW DIRECTIVES FOR DElNING THE ATTRIBUTES AND BODY CONTENT 3O WHY ARE TAGS AND 4AG &ILES DONE DIFFERENTLY

9ES )N FACT IF YOU MAKE A 4,$ THAT REFERENCES YOUR 4AG &ILES THE #ONTAINER WILL CONSIDER BOTH 4AG &ILES AND CUSTOM TAGS MENTIONED IN THE SAME 4,$ AS BELONGING TO THE SAME LIBRARY

/N ONE HAND YES IT WOULD HAVE BEEN SIMPLER IF CUSTOM TAGS AND 4AG &ILES WERE DECLARED IN THE SAME WAY USING A 4,$ 4HE QUESTION IS SIMPLER FOR WHOM &OR A CUSTOM TAG DEVELOPER SURE "UT 4AG &ILES WERE ADDED TO THE SPEC WITH SOMEONE ELSE IN MINDÂ&#x2C6;PAGE DESIGNERS

4AG &ILES GIVE NON *AVA DEVELOPERS A WAY TO BUILD CUSTOM TAGS WITHOUT WRITING A *AVA CLASS TO HANDLE THE TAG S FUNCTIONALITY !ND NOT HAVING TO BUILD A 4,$ FOR THE 4AG &ILE JUST MAKES LIFE EASIER FOR THE 4AG &ILE DEVELOPER 2EMEMBER 4AG &ILES DO NEED A 4,$ IF THE 4AG &ILE IS DEPLOYED IN THE *!2 BUT A NON *AVA PROGRAMMER MIGHT NOT BE USING *!2S ANYWAY

(OLD ONÂ&#x2C6;) THOUGHT YOU SAID 4AG &ILES DIDN T HAVE A 4,$ )SN T THAT WHY YOU HAVE TO USE AN ATTRIBUTE DIRECTIVE 3INCE YOU CAN T DECLARE THE ATTRIBUTE IN A 4,$

4RICK QUESTION )F YOU DEPLOY YOUR 4AG &ILES IN A *!2 THEY -534 HAVE A 4,$ THAT DESCRIBES THEIR LOCATION "UT IT DOESN T DESCRIBE ATTRIBUTE BODY CONTENT ETC 4HE

4HE BOTTOM LINE CUSTOM TAGS MUST HAVE A 4,$ BUT 4AG &ILES CAN DECLARE ATTRIBUTES AND BODY CONTENT DIRECTLY INSIDE THE 4AG &ILE AND NEED 4,$S ONLY IF THE 4AG &ILE IS IN A *!2

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?PMV aW] VMML UWZM \PIV <IO .QTM[ ;WUM\QUM[ aW] VMML 2I^I 4AG &ILES ARE lNE WHEN YOU RE DOING AN INCLUDEÂ&#x2C6;WHEN ALL YOU NEED TO HANDLE THE TAG YOU CAN DO FROM ANOTHER *30 RENAMED WITH A TAG EXTENSION AND WITH THE APPROPRIATE DIRECTIVES ADDED "UT SOMETIMES YOU NEED MORE 3OMETIMES YOU NEED GOOD OLD *AVA CODE AND YOU DON T WANT TO DO IT FROM SCRIPTLETS SINCE THAT S WHAT YOU RE TRYING TO PREVENT BY USING TAGS

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7HEN YOU NEED *AVA YOU NEED A CUSTOM TAG HANDLER ! TAG HANDLER AS OPPOSED TO A TAG lLE IS SIMPLY A *AVA CLASS THAT DOES THE WORK OF THE TAG )T S A LITTLE LIKE AN %, FUNCTION EXCEPT MUCH MORE POWERFUL AND mEXIBLE 7HERE %, FUNCTIONS ARE NOTHING MORE THAN STATIC METHODS A TAG HANDLER CLASS HAS ACCESS TO TAG ATTRIBUTES THE TAG BODY AND EVEN THE PAGE CONTEXT SO IT CAN GET SCOPED ATTRIBUTES AND THE REQUEST AND RESPONSE

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#USTOM TAG HANDLERS COME IN TWO mAVORS #LASSIC AND 3IMPLE #LASSIC TAGS WERE ALL YOU HAD IN THE PREVIOUS VERSION OF *30 BUT WITH *30 A NEW AND MUCH SIMPLER MODEL WAS ADDED 9OU LL HAVE A HARD TIME COMING UP WITH REASONS TO USE THE CLASSIC MODEL WHEN YOU NEED A CUSTOM TAG HANDLER BECAUSE THE SIMPLE MODEL ESPECIALLY COMBINED WITH *34, AND TAG lLES CAN HANDLE NEARLY ANYTHING YOU D WANT TO DO "UT WE CAN T DUMP THE CLASSIC MODEL FOR TWO REASONS AND THESE TWO REASONS ARE WHY YOU STILL HAVE TO LEARN IT FOR THE EXAM

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,IKE SCRIPTING #LASSIC TAG HANDLERS ARE OUT THERE AND YOU MIGHT NEED TO READ AND SUPPORT THEM EVEN IF YOU NEVER CREATE ONE YOURSELF 4HERE ARE THOSE RARE SCENARIOS FOR WHICH A CLASSIC TAG HANDLER IS THE BEST CHOICE 4HIS IS PRETTY OBSCURE THOUGH 3O POINT IS BY FAR THE MOST IMPORTANT REASON TO LEARN ABOUT #LASSIC TAGS

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5ISQVO I ;QUXTM \IO PIVLTMZ &OR THE SIMPLEST OF 3IMPLE TAGS THE PROCESS IS SIMPLE

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The doTag() method declares an IOEx you donĂ&#x2022;t have to wrap the print in a ception, so try/catch.

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) ;QUXTM \IO _Q\P I JWLa )F THE TAG NEEDS A BODY THE 4,$ BODY CONTENT NEEDS TO REmECT THAT AND YOU NEED A SPECIAL STATEMENT IN THE DO4AG METHOD 7KH -63 WKDW XVHV WKH WDJ # WDJOLE SUHÂż[ Â´P\7DJVÂ´ XUL Â´VLPSOH7DJVÂ´ ! KWPO! ERG\! 6LPSOH 7DJ

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<PM ;QUXTM \ IO )81 ! 3IMPLE TAG HANDLER MUST IMPLEMENT THE 3IMPLE4AG INTERFACE 4HE EASIEST WAY TO DO THAT IS TO EXTEND 3IMPLE4AG3UPPORT AND OVERRIDE JUST THE METHOD YOU NEED DO4AG 9OU DON T HAVE TO USE 3IMPLE4AG3UPPORT BUT WE RECKON OF SIMPLE TAG DEVELOPERS DO -VS7DJ LQWHUIDFH MDYD[ VHUYOHW MVS WDJH[W -VS7DJ

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These are the lifecyclener calls methods... the Contai is invoked. these whenever a tag er in Can you guess the ordare called? which these methods

You extend this!

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SimpleTagSupp of SimpleTag (bort implements the methods anything, so yo ut the doTag() doesnĂ&#x2022;t do tag handler). Itu must override it in your convenience me also adds three more useful oneĂ&#x2018;getJthods, including the most spBody().

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<PM TQNM WN I ;QUXTM \IO PIVLTMZ 7HEN A *30 INVOKES A TAG A NEW INSTANCE OF THE TAG HANDLER CLASS IS INSTANTIATED TWO OR MORE METHODS ARE CALLED ON THE HANDLER AND WHEN THE DO4AG METHOD COMPLETES THE HANDLER OBJECT GOES AWAY )N OTHER WORDS THESE HANDLER OBJECTS ARE NOT REUSED :HE &RQWDLQHU

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This gives the handler a reference to a PageContext (a subclass of JspContext ).

A nested tag canh the other communicate wit nested ! tags in which itĂ&#x2022;s If the tag is invoked attributes, the setterwith each attribute is called, usingfor JavaBean naming. (ThereĂ&#x2022;s a special exception to this that weĂ&#x2022;ll see later.) y, the body If the tag has a bod s method, as comes in through thi nt. an instance of JspFragme

Now weĂ&#x2022;re Ă&#x17E;nally rea DO what the tag is meantdytotodo!

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?PI\ QN \PM \IO JWLa ][M[ IV M`XZM[[QWV' )MAGINE YOU HAVE A TAG WITH A BODY THAT USES AN %, EXPRESSION FOR AN ATTRIBUTE .OW IMAGINE THAT THE ATTRIBUTE DOESN T EXIST AT THE TIME YOU INVOKE THE TAG )N OTHER WORDS THE TAG BODY DEPENDS ON THE TAG HANDLER TO SET THE ATTRIBUTE 4HE EXAMPLE DOESN T DO ANYTHING VERY USEFUL BUT IT S HERE TO SHOW YOU HOW IT WORKS IN PREPARATION FOR A BIGGER EXAMPLE 7KH -63 WDJ LQYRFDWLRQ P\7DJV VLPSOH ! 0HVVDJH LV ^PHVVDJH` P\7DJV VLPSOH !

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) \IO _Q\P LaVIUQK ZW_ LI\I" Q\MZI\QVO \PM JWLa )N THIS EXAMPLE THE %, EXPRESSION IN THE BODY OF THE TAG REPRESENTS A SINGLE VALUE IN A COLLECTION AND THE GOAL IS TO HAVE THE TAG GENERATE ONE ROW FOR EACH ELEMENT IN THE COLLECTION )T S SIMPLEÂ&#x2C6;THE DO4AG METHOD SIMPLY DOES THE WORK IN A LOOP INVOKING THE BODY ON EACH ITERATION OF THE LOOP 7KH -63 WDJ LQYRFDWLRQ WDEOH! P\7DJV VLPSOH ! WU! WG! ^PRYLH` WG! WU! P\7DJV VLPSOH ! WDEOH!

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Each loop of the Tag dle r resets the Ă&#x2019;movieĂ&#x201C; attribute han value and calls getJspBody().invoke() aga in.

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Chapter 10. When even JSTL is not enough...

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ItĂ&#x2022;s just an attribute like any other tag attribute. It doesnĂ&#x2022;t that itĂ&#x2022;s a Simple Tag han matter dler taking care of the tag.

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?PI\ M`IK\Ta 1; I 2[X.ZIOUMV\' ! *SP&RAGMENT IS AN OBJECT THAT REPRESENTS *30 CODE )TS SOLE PURPOSE IN LIFE IS TO BE INVOKED )N OTHER WORDS IT S SOMETHING THAT S MEANT TO RUN AND GENERATE OUTPUT 4HE BODY OF A TAG THAT INVOKES A SIMPLE TAG HANDLER IS ENCAPSULATED IN THE *SP&RAGMENT OBJECT THEN SENT TO THE TAG HANDLER IN THE SET*SP"ODY METHOD 4HE CRUCIAL THING YOU MUST REMEMBER ABOUT *SP&RAGMENT IS THAT IT MUST ./4 CONTAIN ANY SCRIPTING ELEMENTS )T CAN CONTAIN TEMPLATE TEXT STANDARD AND CUSTOM ACTIONS AND %, EXPRESSIONS BUT NO SCRIPTLETS DECLARATIONS OR SCRIPTING EXPRESSIONS /NE COOL THING IS THAT SINCE IT S AN OBJECT YOU CAN EVEN PASS THE FRAGMENT AROUND TO OTHER HELPER OBJECTS !ND THOSE OBJECTS IN TURN CAN GET INFORMATION FROM IT BY INVOKING THE *SP&RAGMENT S OTHER METHODÂ&#x2C6;GET*SP#ONTEXT !ND OF COURSE ONCE YOU VE GOT A CONTEXT YOU CAN ASK FOR ATTRIBUTES 3O THE GET*SP#ONTEXT METHOD IS REALLY A WAY FOR THE TAG BODY TO GET INFORMATION TO OTHER OBJECTS -OST OF THE TIME THOUGH YOU LL USE *SP&RAGMENT SIMPLY TO OUTPUT THE BODY OF THE TAG TO THE RESPONSE 9OU MIGHT HOWEVER WANT TO GET ACCESS TO THE CONTENTS OF THE BODY .OTICE THAT *SP&RAGMENT DOESN T HAVE AN ACCESS METHOD LIKE GET#ONTENTS OR GET"ODY 9OU CAN WRITE THE BODY TO SOMETHING BUT YOU CAN T DIRECTLY GET THE BODY )F YOU DO WANT ACCESS TO THE BODY YOU CAN USE THE ARGUMENT TO THE INVOKE METHOD TO PASS IN A JAVA IO 7RITER THEN USE METHODS ON THAT 7RITER TO PROCESS THE CONTENTS OF THE TAG BODY

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$O THE ATTRIBUTE METHODS IN A 3IMPLE4AG HANDLER HAVE TO BE OF A TYPE THAT CAN BE AUTOMATICALLY CONVERTED TO AND FROM A 3TRING )N OTHER WORDS ARE YOU STUCK WITH JUST PRIMITIVES AND 3TRING VALUES

7EREN T YOU PAYING ATTENTION A FEW PAGES BACK 4HE ATTRIBUTE WE SENT TO THE 3IMPLE4AG HANDLER WAS AN !RRAY,IST OF MOVIES 3O THAT WOULD BE hNOv TO ANSWER YOUR QUESTION "UT IF THE ATTRIBUTE WHICH YOU CAN THINK OF AS A PROPERTY IF YOU THINK OF THE 3IMPLE4AG HANDLER AS A BEAN IS ./4 A 3TRING OR PRIMITIVE THEN THE RTEXPRVALUE VALUE IN THE 4,$ HAD BETTER BE SET TO TRUE "ECAUSE THAT S

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)N A 3IMPLE4AG HANDLER IF THE TAG IS DECLARED TO HAVE A BODY BUT IT IS INVOKED USING AN EMPTY TAG SINCE THERE S NO WAY TO SAY THAT A BODY IS REQUIRED IS THE SET*SP"ODY STILL INVOKED

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Chapter 10. When even JSTL is not enough...

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) +TI[[QK \IO PIVLTMZ _Q\P <?7 UM\PWL[ 4HIS EXAMPLE OVERRIDES BOTH THE DO3TART4AG AND DO%ND4AG METHODS ALTHOUGH IT COULD ACCOMPLISH THE SAME OUTPUT ALL WITHIN DO3TART4AG 4HE POINT OF DO%ND4AG IS THAT IT S CALLED AFTER THE BODY IS EVALUATED 7E DON T SHOW THE 4,$ HERE BECAUSE IT S VIRTUALLY IDENTICAL TO THE PREVIOUS ONE EXCEPT FOR SOME OF THE NAMES 4HE TAG IS DECLARED TO HAVE NO ATTRIBUTES AND AN EMPTY BODY $ -63 WKDW LQYRNHV D &ODVVLF WDJ # WDJOLE SUHÂż [ Â´PLQHÂ´ XUL Â´.DWK\&ODVVLF7DJVÂ´ ! KWPO! ERG\! &ODVVLF 7DJ 7ZR EU! PLQH FODVVLF7ZR ! ERG\! KWPO!

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?PMV I \IO PI[ I JWLa" KWUXIZQVO ;QUXTM ^[ +TI[[QK .OW IT STARTS TO LOOK DIFFERENT FROM A 3IMPLE4AG 2EMEMBER 3IMPLE4AG BODIES ARE EVALUATED WHEN AND IF YOU WANT BY CALLING INVOKE ON THE *SP&RAGMENT THAT ENCAPSULATES THE BODY "UT IN #LASSIC TAGS THE BODY IS EVALUATED IN BETWEEN THE DO3TART4AG AND DO%ND4AG METHODS "OTH OF THE EXAMPLES BELOW HAVE THE EXACT SAME BEHAVIOR 7KH -63 WKDW XVHV WKH WDJ # WDJOLE SUHÂ¿[ Â´P\7DJVÂ´ XUL Â´P\7DJVÂ´ ! KWPO! ERG\!

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evaluated.

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+TI[[QK \IO[ PI^M I LQNNMZMV\ TQNMKaKTM 3IMPLE TAGS ARE SIMPLEÂ&#x2C6;IT S ALL ABOUT DO4AG "UT WITH CLASSIC TAGS THERE S A DO3TART4AG AND A DO%ND4AG !ND THAT BRINGS UP AN INTERESTING PROBLEMÂ&#x2C6;WHEN AND HOW IS THE BODY EVALUATED 4HERE S NO DO"ODY METHOD BUT THERE IS A DO!FTER"ODY METHOD THAT S CALLED AFTER THE BODY IS EVALUATED AND BEFORE THE DO%ND4AG RUNS :HE &RQWDLQHU

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Tag (extends JspTag) IterationTag (extends Tag) BodyTag (extends IterationTag) TagSupport (implements IterationTag) BodyTagSupport (extends TagSupport, implements BodyTag) doStartTag() doEndTag() doAfterBody() (and for BodyTagĂ&#x2018; doInitBody() and setBodyContent()) pageContext.getOut().println (wrapped in a try/catch because Classic tag methods do NOT declare the IOException!) With the pageContext implicit variable--NOT a method like it is with SimpleTag! Return EVAL_BODY_INCLUDE from doStartTag(), or EVAL_BODY_BUFFERED if the class implements BodyTag. Return SKIP_PAGE from doEndTag()

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Chapter 10. When even JSTL is not enough...

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Chapter 10. When even JSTL is not enough...

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(OW CAN A #LASSIC TAG HANDLER TO INSTRUCT THE CONTAINER TO IGNORE THE REMAINDER OF THE *30 THAT INVOKED THE TAG #HOOSE ALL THAT APPLY

R ! 4HE GR(QG7DJ METHOD SHOULD RETURN 7DJ 6.,3B%2'<

R " 4HE GR(QG7DJ METHOD SHOULD RETURN 7DJ 6.,3B3$*( R # 4HE GR6WDUW7DJ METHOD SHOULD RETURN 7DJ 6.,3B%2'< R $ 4HE GR6WDUW7DJ METHOD SHOULD RETURN 7DJ 6.,3B3$*(

7HICH DIRECTIVES AND OR STANDARD ACTIONS ARE APPLICABLE /.,9 WITHIN TAG lLES #HOOSE ALL THAT APPLY

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Chapter 10. When even JSTL is not enough...

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'IVEN A *30 PAGE P\ WDJ ! P\ WDJ ! P\ WDJ ! P\ WDJ ! P\ WDJ ! 4HE TAG HANDLER FOR P\ WDJ IS 7DJ +DQGOHU AND EXTENDS 4AG3UPPORT 4HE TAG HANDLER FOR P\ WDJ IS 7DJ +DQGOHU AND EXTENDS 3IMPLE4AG3UPPORT 4HE TAG HANDLER FOR P\ WDJ IS 7DJ +DQGOHU AND EXTENDS 4AG3UPPORT 7HICH IS TRUE #HOOSE ALL THAT APPLY

R ! 7DJ +DQGOHU #!../4 ACCESS THE INSTANCE OF 7DJ +DQGOHU BECAUSE 3IMPLE TAGS DO ./4 SUPPORT ACCESS TO THE TAG PARENT R " /NLY #LASSIC TAGS ARE CONSIDERED IN COMPOSING THE PARENT CHILD TAG HIEARCHY THEREFORE 7DJ +DQGOHU MAY USE THE JHW3DUHQW METHOD ONLY ONCE TO GAIN ACCESS TO THE INSTANCE OF 7DJ +DQGOHU

R # 7DJ +DQGOHU MAY USE THE JHW3DUHQW METHOD TWICE TO GAIN ACCESS TO THE INSTANCE OF 7DJ +DQGOHU

R $ /NLY "ODY4AG HANDLERS CAN ACCESS THE PARENT CHILD TAG HIEARCHY THEREFORE 7DJ +DQGOHU #!../4 GAIN ACCESS TO THE INSTANCE OF 7DJ +DQGOHU

7HICH 3IMPLE TAG MECHANISM WILL TELL A *30 PAGE TO STOP PROCESSING

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Chapter 10. When even JSTL is not enough...

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7HICH ARE TRUE ABOUT THE #LASSIC TAG MODEL #HOOSE ALL THAT APPLY

R ! 4HE 7DJ INTERFACE CAN ONLY BE USED TO CREATE EMPTY TAGS

R " 4HE 6.,3B3$*( CONSTANT IS A VALID RETURN VALUE OF THE GR(QG7DJ METHOD

R # 4HE (9$/B%2'<B%8))(5(' CONSTANT IS A VALID RETURN VALUE OF THE GR$IWHU%RG\ METHOD

R $ 4HE 7DJ INTERFACE ONLY PROVIDES TWO VALUES FOR THE RETURN VALUE OF THE GR6WDUW7DJ METHOD 6.,3B%2'< AND (9$/B%2'<

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R ! )T REQUIRES ONE PARAMETER ! &ODVV R " )T IS A STATIC METHOD IN THE 7DJ6XSSRUW CLASS R # )T IS A NON STATIC METHOD IN THE 7DJ6XSSRUW CLASS R $ )T IS ./4 DElNED BY ANY OF THE STANDARD *30 TAG INTERFACES R % )T REQUIRES TWO PARAMETERS ! 7DJ AND A &ODVV R & )T REQUIRES ONE PARAMETER ! 6WULQJ REPRESENTING THE NAME OF THE TAG TO BE FOUND

R ' )T REQUIRES TWO PARAMETERS ! 7DJ AND A 6WULQJ REPRESENTING THE NAME OF THE TAG TO BE FOUND

\RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN H[DP

7HICH MUST BE TRUE IF YOU WANT TO USE DYNAMIC ATTRIBUTES FOR A 3IMPLE TAG HANDLER #HOOSE ALL THAT APPLY

R ! 9OUR 3IMPLE TAG MUST ./4 DECLARE ANY STATIC TAG ATTRIBUTES

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R # 9OUR 3IMPLE TAG HANDLER MUST IMPLEMENT THE '\QDPLF$WWULEXWHV INTERFACE

R $ 9OUR 3IMPLE TAG SHOULD EXTEND THE '\QDPLF6LPSOH7DJ6XSSRUW CLASS WHICH PROVIDES DEFAULT SUPPORT FOR DYNAMIC ATTRIBUTES

R % 9OUR 3IMPLE TAG #!../4 BE USED WITH THE MVS DWWULEXWH STANDARD ACTION BECAUSE THIS ACTION WORKS ONLY WITH STATIC ATTRIBUTES

7HICH IS TRUE ABOUT TAG lLES #HOOSE ALL THAT APPLY

R ! ! TAG lLE MAY BE PLACED IN ANY SUBDIRECTORY OF :(% ,1) R " ! TAG lLE MUST HAVE THE lLE EXTENSION OF WDJ OR WDJ[ R # ! 4,$ lLE MUST BE USED TO MAP THE SYMBOLIC TAG NAME TO THE ACTUAL TAG lLE

R $ ! TAG lLE MAY ./4 BE PLACED IN A *!2 lLE IN THE :(% ,1) OLE DIRECTORY

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Chapter 10. When even JSTL is not enough...

FXVWRP WDJ GHYHORSPHQW

'IVEN SXEOLF FODVV %XI7DJ H[WHQGV %RG\7DJ6XSSRUW ^ SXEOLF LQW GR6WDUW7DJ WKURZV -VS([FHSWLRQ ^ LQVHUW FRGH KHUH ` ` !SSUME THAT THE TAG HAS BEEN PROPERLY CONlGURED TO ALLOW BODY CONTENT 7HICH IF INSERTED AT LINE WOULD CAUSE THE *30 CODE P\WDJV P\WDJ!%RG\&RQWHQW P\WDJV P\WDJ! TO OUTPUT %RG\&RQWHQW

R ! UHWXUQ 6.,3B%2'< R " UHWXUQ (9$/B%2'<B,1&/8'( R # UHWXUQ (9$/B%2'<B%8))(5(' R $ UHWXUQ %2'<B&217(17

7HICH ABOUT GR$IWHU%RG\ IS TRUE #HOOSE ALL THAT APPLY

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R " GR$IWHU%RG\ IS ONLY CALLED ON TAGS THAT EXTEND ,WHUDWLRQ7DJ6XSSRUW

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R % !SSUMING NO EXCEPTIONS OCCUR GR$IWHU%RG\ IS CALLED AFTER GR6WDUW7DJ FOR ANY TAG THAT IMPLEMENTS ,WHUDWLRQ7DJ AND RETURNS (9$/B%2'<B,1&/8'( FROM GR6WDUW7DJ \RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN H[DP

'IVEN A *30 PAGE

# WDJOLE SUHÂ¿[ Â´P\Â´ XUL Â´ :(% ,1) P\7DJV WOGÂ´ ! P\ WDJ ! -63 FRQWHQW ! P\ WDJ ! 4HE TAG HANDLER FOR P\ WDJ IS 7DJ +DQGOHU AND EXTENDS 4AG3UPPORT 7HAT HAPPENS WHEN THE INSTANCE OF 7DJ +DQGOHU CALLS THE JHW3DUHQW METHOD #HOOSE ALL THAT APPLY

R ! ! -VS([FHSWLRQ IS THROWN R " 4HE QXOO VALUE IS RETURNED R # ! 1XOO3RLQWHU([FHSWLRQ IS THROWN R $ !N ,OOHJDO6WDWH([FHSWLRQ IS THROWN

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R # 4HE VHW3DUHQW AND VHW-VS&RQWH[W METHODS ARE CALLED IMMEDIATELY BEFORE THE TAG ATTRIBUTES ARE SET

R $ 4HE -VS)UDJPHQW OF THE TAG BODY IS INVOKED BY THE #ONTAINER BEFORE THE TAG HANDLER S GR7DJ METHOD IS CALLED 4HIS VALUE A %RG\&RQWHQW OBJECT IS PASSED TO THE TAG HANDLER USING THE VHW-VS%RG\ METHOD

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Chapter 10. When even JSTL is not enough...

FXVWRP WDJ GHYHORSPHQW

(JSP v2.0 pg 2-27)

'IVEN SXEOLF FODVV ([DPSOH7DJ H[WHQGV 7DJ6XSSRUW ^ SULYDWH 6WULQJ SDUDP SXEOLF YRLG VHW3DUDP 6WULQJ S ^ SDUDP S ` SXEOLF LQW GR6WDUW7DJ WKURZV -VS([FHSWLRQ ^ LQVHUW FRGH KHUH PRUH FRGH KHUH ` `

7HICH INSERTED AT LINE WOULD BE GUARANTEED TO ASSIGN THE VALUE OF THE REQUEST SCOPED ATTRIBUTE SDUDP TO THE LOCAL VARIABLE S #HOOSE ALL THAT APPLY

-Option A is invalid because there is no such method. -Option B is invalid because there is UHTXHVW JHW$WWULEXWH ÂłSDUDPÂ´ no request instance variable.

R ! 6WULQJ S ÂżQG$WWULEXWH ÂłSDUDPÂ´ R " 6WULQJ S

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7HICH ARE VALID METHOD CALLS ON A 3DJH&RQWH[W OBJECT #HOOSE ALL THAT APPLY

(JSP v2.0 pg. 2-

23)

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R % JHW$WWULEXWHV6FRSH ÂłNH\Â´

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\RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN H[DP

7HICH IS THE MOST EFlCIENT -VS&RQWH[W METHOD TO CALL TO ACCESS AN ATTRIBUTE THAT IS KNOWN TO BE IN APPLICATION SCOPE

R ! JHW3DJH&RQWH[W

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R # Â¿QG$WWULEXWH 6WULQJ R $ JHW$WWULEXWH 6WULQJ LQW

R % JHW$WWULEXWHV6FRSH Â³NH\Â´

R & JHW$WWULEXWH1DPHV,Q6FRSH LQW

7HAT IS THE BEST STRATEGY WHEN IMPLEMENTING A CUSTOM TAG FOR lNDING THE VALUE OF AN ATTRIBUTE WHOSE SCOPE IS UNKNOWN

R ! #HECK ALL SCOPES WITH A SINGLE SDJH&RQWH[W JHW$WWULEXWH 6WULQJ CALL

R " #HECK ALL SCOPES WITH A SINGLE SDJH&RQWH[W Â¿QG$WWULEXWH 6WULQJ CALL

R # #HECK EACH SCOPE WITH CALLS TO SDJH&RQWH[W JHW$WWULEXWH 6WULQJ LQW

R $ #ALL SDJH&RQWH[W JHW5HTXHVW JHW$WWULEXWH 6WULQJ

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R % .ONE OF THESE WILL WORK

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Chapter 10. When even JSTL is not enough...

FXVWRP WDJ GHYHORSPHQW

'IVEN A TAG VLPSOH7DJ WHOSE HANDLER IS IMPLEMENTED USING THE 3IMPLE TAG MODEL AND A TAG FRPSOH[7DJ WHOSE HANDLER IS IMPLEMENTED USING THE #LASSIC TAG MODEL "OTH TAGS ARE DECLARED TO BE NON EMPTY IN THE 4,$ 7HICH *30 CODE SNIPPETS ARE VALID USES OF THESE TAG #HOOSE ALL THAT APPLY

R ! P\ VLPSOH7DJ! P\ FRPSOH[7DJ ! P\ VLPSOH7DJ!

R " P\ VLPSOH7DJ! GLVSOD\7H[W ! P\ VLPSOH7DJ!

R # P\ VLPSOH7DJ! # LQFOXGH Â¿OH Â´ :(% ,1) ZHE FRPPRQ KHDGHU0HQX KWPOÂ´ ! P\ VLPSOH7DJ!

R $ P\ VLPSOH7DJ! P\ FRPSOH[7DJ! L ! P\ FRPSOH[7DJ! P\ VLPSOH7DJ!

7HICH ARE TRUE ABOUT THE 4AG &ILE MODEL #HOOSE ALL THAT APPLY

R ! %ACH TAG lLE MUST HAVE A CORRESPONDING ENTRY IN A 4,$ lLE R " !LL DIRECTIVES ALLOWED IN *30 PAGES ARE ALLOWED IN 4AG &ILES

R # !LL DIRECTIVES ALLOWED IN 4AG &ILES ARE ALLOWED IN *30 PAGES

R $ 4HE MVS GR%RG\! STANDARD ACTION CAN ONLY BE USED IN 4AG &ILES

R % 4HE ALLOWABLE lLE EXTENSIONS FOR 4AG &ILES ARE WDJ AND WDJ[

R & &OR EACH ATTRIBUTE DECLARED AND SPECIlED IN A 4AG &ILE THE CONTAINER CREATES A PAGE SCOPED ATTRIBUTE WITH THE SAME NAME \RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN H[DP

7HICH ARE VALID IN TAG lLES #HOOSE ALL THAT APPLY

R ! MVS GR%RG\ ! R " MVS LQYRNH IUDJPHQW Â´IUDJÂ´ ! R # # SDJH LPSRUW Â´MDYD XWLO 'DWHÂ´ ! R $ # YDULDEOH QDPH JLYHQ Â´GDWHÂ´ YDULDEOH FODVV Â´MDYD XWLO 'DWHÂ´ !

R % # DWWULEXWH QDPH Â´QDPHÂ´ YDOXH Â´EODQNÂ´ W\SH Â´MDYD ODQJ 6WULQJÂ´ !

7HICH RETURNS THE ENCLOSING TAG WHEN CALLED FROM WITHIN A TAG HANDLER CLASS #HOOSE ALL THAT APPLY

R ! JHW3DUHQW

R " JHW$QFHVWRU

R # Â¿QG$QFHVWRU R $ JHW(QFORVLQJ7DJ

'IVEN A WEB APPLICATION STURCUTRE :(% ,1) WDJV P\WDJV WDJ WDJ :(% ,1) WDJV WDJ WDJ :(% ,1) WDJ WDJ WDJ WDJ 7HICH TAGS COULD BE USED BY AN APPROPRIATE WDJOLE DIRECTIVE #HOOSE ALL THAT APPLY

R ! WDJ WDJ R " WDJ WDJ R # WDJ WDJ R $ WDJ WDJ

FKDSWHU

Chapter 10. When even JSTL is not enough...

FXVWRP WDJ GHYHORSPHQW

&KDSWHU $QVZHUV

(OW CAN A #LASSIC TAG HANDLER TO INSTRUCT THE CONTAINER TO IGNORE THE REMAINDER OF THE *30 THAT INVOKED THE TAG #HOOSE ALL THAT APPLY

R ! 4HE GR(QG7DJ METHOD SHOULD RETURN 7DJ 6.,3B%2'<

56)

(JSP v2.0 pg 2-

alid because thr is -Option A is invret urn value fo id val a t no is (). ag dT En do

R " 4HE GR(QG7DJ METHOD SHOULD RETURN 7DJ 6.,3B3$*( R # 4HE GR6WDUW7DJ METHOD SHOULD RETURN 7DJ 6.,3B%2'<

-Option C is invalid because it only causes the body of the tag to be skipped.

R $ 4HE GR6WDUW7DJ METHOD SHOULD RETURN 7DJ 6.,3B3$*( -Option D is invalid becaus

e this is not a valid ret doStartTag(). urn value for

7HICH DIRECTIVES AND OR STANDARD ACTIONS ARE APPLICABLE /.,9 WITHIN TAG lLES #HOOSE ALL THAT APPLY

R ! WDJ R " SDJH

-Option A is valid (pg 1-179).

(JSP v2.0 8.5 (pg 1-179) JSP v2.0 section 5.11 JSP v2.0 section 5.12 JSP v2.0 section 5.13)

-Option B is invalid because the page directive is never allowed in a tag Ă&#x17E;le (pg 1-179).

R # MVS ERG\

-Option C is invalid because the jsp:body action can appear in EITHER a tag Ă&#x17E;le or JSP.

R $ MVS GR%RG\

- Option D is valid (pg 1-121).

R % MVS LQYRNH

-Option E is valid (pg 1-119).

R & WDJOLE

-Option F is invalid because the taglib directive can appear in EITHER a tag Ă&#x17E;le or JSP.

\RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN DQVZHUV

'IVEN A *30 PAGE P\ WDJ ! P\ WDJ ! P\ WDJ ! P\ WDJ ! P\ WDJ !

(JSP v2.0 SimpleTagSupport API pg 2-86 JSP v2.0 TagSupport API pg 2-64)

4HE TAG HANDLER FOR P\ WDJ IS 7DJ +DQGOHU AND EXTENDS 4AG3UPPORT 4HE TAG HANDLER FOR P\ WDJ IS 7DJ +DQGOHU AND EXTENDS 3IMPLE4AG3UPPORT 4HE TAG HANDLER FOR P\ WDJ IS 7DJ +DQGOHU AND EXTENDS 4AG3UPPORT 7HICH IS TRUE #HOOSE ALL THAT APPLY

-Option A is invalid because getParent method.

R ! 7DJ +DQGOHU #!../4 ACCESS THE INSTANCE OF 7DJ +DQGOHU Simple tags do have a

BECAUSE 3IMPLE TAGS DO ./4 SUPPORT ACCESS TO THE TAG PARENT

R " /NLY #LASSIC TAGS ARE CONSIDERED IN COMPOSING THE PARENT CHILD TAG HIEARCHY THEREFORE 7DJ +DQGOHU MAY USE THE JHW3DUHQW METHOD ONLY ONCE TO GAIN ACCESS TO THE INSTANCE OF 7DJ +DQGOHU

-Option B is invalid because Simple tags do participate in the parent/child tag hierarchy along with Classic tags.

R # 7DJ +DQGOHU MAY USE THE JHW3DUHQW METHOD TWICE TO GAIN ACCESS TO THE INSTANCE OF 7DJ +DQGOHU

R $ /NLY "ODY4AG HANDLERS CAN ACCESS THE PARENT CHILD TAG HIEARCHY -Option D is invalid because THEREFORE 7DJ +DQGOHU #!../4 GAIN ACCESS TO THE INSTANCE OF 7DJ +DQGOHU

7HICH 3IMPLE TAG MECHANISM WILL TELL A *30 PAGE TO STOP PROCESSING

R ! 2ETURN 6.,3B3$*( FROM THE GR7DJ METHOD

every JspTag has access to its parent tag.

(JSP v2.0 section

13.6.1)

-Option A is invalid because the doTag method dies return a value.

R " 2ETURN 6.,3B3$*( FROM THE GR(QG7DJ METHOD -Option B is invalid because a Simple

tag does not have the doEndTag event method.

R # 4HROW A 6NLS3DJH([FHSWLRQ FROM THE GR7DJ METHOD R $ 4HROW A 6NLS3DJH([FHSWLRQ FROM THE GR(QG7DJ METHOD

-Option D is invalid because a Simple tag does not have the doEndTag event method.

FKDSWHU

Chapter 10. When even JSTL is not enough...

FXVWRP WDJ GHYHORSPHQW

sections (JSP v2.0 .2 13.1 and 13 ) ce -Option A is invalid because the Tag interfa can support tags with a body, but you canĂ&#x2022;t iterate or gain access to the body content.

7HICH ARE TRUE ABOUT THE #LASSIC TAG MODEL #HOOSE ALL THAT APPLY

R ! 4HE 7DJ INTERFACE CAN ONLY BE USED TO CREATE EMPTY TAGS

R " 4HE 6.,3B3$*( CONSTANT IS A VALID RETURN VALUE OF THE GR(QG7DJ METHOD

-Option C is invalid because doAfterBody can only return SKIP_BODY or EVAL_BODY_AGAIN.

R # 4HE (9$/B%2'<B%8))(5(' CONSTANT IS A VALID RETURN VALUE OF THE GR$IWHU%RG\ METHOD

R $ 4HE 7DJ INTERFACE ONLY PROVIDES TWO VALUES FOR THE

-Option D is invalid because doStartTag returns SKIP_BODY and EVAL_BODY_INCLUDE.

RETURN VALUE OF THE GR6WDUW7DJ METHOD 6.,3B%2'< AND (9$/B%2'<

R % 4HERE ARE THREE TAG INTERFACES 7DJ ,WHUDWLRQ7DJ AND %RG\7DJ BUT ONLY TWO BUILT IN BASE CLASSES 7DJ6XSSRUW AND %RG\7DJ6XSSRUW

7HICH ABOUT THE ÂżQG$QFHVWRU:LWK&ODVV METHOD ARE TRUE #HOOSE ALL THAT APPLY

64) (JSP v2.0 pg. 2-

R ! )T REQUIRES ONE PARAMETER ! &ODVV R " )T IS A STATIC METHOD IN THE 7DJ6XSSRUW CLASS -Option C is invalid because the R # )T IS A NON STATIC METHOD IN THE 7DJ6XSSRUW CLASS method is static. R $ )T IS ./4 DElNED BY ANY OF THE STANDARD *30 TAG INTERFACES R % )T REQUIRES TWO PARAMETERS ! 7DJ AND A &ODVV R & )T REQUIRES ONE PARAMETER ! 6WULQJ REPRESENTING THE -Options A and F are invalid because NAME OF THE TAG TO BE FOUND

R ' )T REQUIRES TWO PARAMETERS ! 7DJ AND A 6WULQJ REPRESENTING THE NAME OF THE TAG TO BE FOUND

the method takes two parameters.

-Option G is invalid because the second argument is a Class.

\RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN DQVZHUV

7HICH MUST BE TRUE IF YOU WANT TO USE DYNAMIC ATTRIBUTES FOR A 3IMPLE TAG HANDLER #HOOSE ALL THAT APPLY

(JSP v2.0 section 13.3 pgs 2-74,75)

you -Option A is invalid becausedyna mic can have both static and attributes in a Simple tag.

R ! 9OUR 3IMPLE TAG MUST ./4 DECLARE ANY STATIC TAG ATTRIBUTES

R " 9OUR 3IMPLE TAG MUST USE THE G\QDPLF DWWULEXWHV! ELEMENT IN THE 4,$

R # 9OUR 3IMPLE TAG HANDLER MUST IMPLEMENT THE '\QDPLF$WWULEXWHV INTERFACE

R $ 9OUR 3IMPLE TAG SHOULD EXTEND THE

-Option D is invalid because there is no such helper class in the builtin APIs.

'\QDPLF6LPSOH7DJ6XSSRUW CLASS WHICH PROVIDES DEFAULT SUPPORT FOR DYNAMIC ATTRIBUTES

R % 9OUR 3IMPLE TAG #!../4 BE USED WITH THE

-Option E is invalid because you are allowed to use the jsp:attribute action with dynamic tags.

MVS DWWULEXWH STANDARD ACTION BECAUSE THIS ACTION WORKS ONLY WITH STATIC ATTRIBUTES

(JSP v2.0 section

7HICH IS TRUE ABOUT TAG lLES #HOOSE ALL THAT APPLY

R ! ! TAG lLE MAY BE PLACED IN ANY SUBDIRECTORY OF :(% ,1)

8.4)

-Option A is invalid because tag Ă&#x17E;les must be placed under the WEB-INF/ tags directory.

R " ! TAG lLE MUST HAVE THE lLE EXTENSION OF WDJ OR WDJ[ -Option B is correct (pg 1-176, 8.4.1). R # ! 4,$ lLE MUST BE USED TO MAP THE SYMBOLIC TAG NAME TO THE ACTUAL TAG lLE

-Option C is invalid because tag Ă&#x17E;les may be discovered by the container in several well-known locations. This container feature is optional.

R $ ! TAG lLE MAY ./4 BE PLACED IN A *!2 lLE IN THE :(% ,1) OLE DIRECTORY

FKDSWHU

Chapter 10. When even JSTL is not enough...

FXVWRP WDJ GHYHORSPHQW

(JSP v2.0 pg. 2-68)

-Option A is invalid because it causes the

R ! UHWXUQ 6.,3B%2'< body of the tag to be skipped. R " UHWXUQ (9$/B%2'<B,1&/8'( - Option C is invalid because it directs the body of R # UHWXUQ (9$/B%2'<B%8))(5(' the tag to a buffer which this tag does not process. R $ UHWXUQ %2'<B&217(17 -Option

D is invalid because you can store tag Ă&#x17E;les in JAR Ă&#x17E;les, under the META-INF/ta gs directory.

(JSP v2.0 pg. 1-152)

7HICH ABOUT GR$IWHU%RG\ IS TRUE #HOOSE ALL THAT APPLY

doAfterBody() R ! GR$IWHU%RG\ IS ONLY CALLED ON TAGS -Option A is invalid because tag that implements the THAT EXTEND 7DJ6XSSRUW

R " GR$IWHU%RG\ IS ONLY CALLED ON TAGS THAT EXTEND ,WHUDWLRQ7DJ6XSSRUW

can be called on any IteratorTag interface.

-Option B is invalid because there is no such class.

R # !SSUMING NO EXCEPTIONS OCCUR GR$IWHU%RG\ IS ALWAYS CALLED AFTER GR6WDUW7DJ FOR ANY TAG THAT IMPLEMENTS ,WHUDWLRQ7DJ

R $ !SSUMING NO EXCEPTIONS OCCUR GR$IWHU%RG\ IS

-Options C and D are invalid because doAfterBody() is only called when doStartTag() returns EVAL_BODY_INCLUDE.

CALLED AFTER GR6WDUW7DJ FOR ANY TAG THAT IMPLEMENTS ,WHUDWLRQ7DJ AND RETURNS 6.,3B%2'< FROM GR6WDUW7DJ

R % !SSUMING NO EXCEPTIONS OCCUR GR$IWHU%RG\ IS CALLED AFTER GR6WDUW7DJ FOR ANY TAG THAT IMPLEMENTS ,WHUDWLRQ7DJ AND RETURNS (9$/B%2'<B,1&/8'( FROM GR6WDUW7DJ \RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN DQVZHUV

(JSP v2.0 TagSupport API pg 2-64)

'IVEN A *30 PAGE

R ! ! -VS([FHSWLRQ IS THROWN

-Option B is the correct answer. The ent method does not throw any

getPar R " 4HE QXOO VALUE IS RETURNED exceptions. R # ! 1XOO3RLQWHU([FHSWLRQ IS THROWN R $ !N ,OOHJDO6WDWH([FHSWLRQ IS THROWN

7HICH IS TRUE ABOUT THE LIFECYCLE OF A 3IMPLE TAG #HOOSE ALL THAT APPLY

R ! 4HE UHOHDVH METHOD IS CALLED AFTER THE GR7DJ METHOD R " 4HE VHW-VS%RG\ METHOD IS ALWAYS CALLED BEFORE THE GR7DJ METHOD

(JSP v2.0 section 13.6 pgs 2-80/83) -Option A is invalid because a Simple tag has no release method.

-Option B is invalid because the setJspBody is not called if the Simple tag is an empty tag.

R # 4HE VHW3DUHQW AND VHW-VS&RQWH[W METHODS ARE CALLED IMMEDIATELY BEFORE THE TAG ATTRIBUTES ARE SET

-Option D is invalid because the fragment is invoked by the doTag implementation, NOT before the doTag is called.

FKDSWHU

Chapter 10. When even JSTL is not enough...

FXVWRP WDJ GHYHORSPHQW

(JSP v2.0 pg 2-27)

'IVEN SXEOLF FODVV ([DPSOH7DJ H[WHQGV 7DJ6XSSRUW ^ SULYDWH 6WULQJ SDUDP SXEOLF YRLG VHW3DUDP 6WULQJ S ^ SDUDP S ` SXEOLF LQW GR6WDUW7DJ WKURZV -VS([FHSWLRQ ^ LQVHUW FRGH KHUH PRUH FRGH KHUH ` `

7HICH INSERTED AT LINE WOULD BE GUARANTEED TO ASSIGN THE VALUE OF THE REQUEST SCOPED ATTRIBUTE SDUDP TO THE LOCAL VARIABLE S #HOOSE ALL THAT APPLY

-Option A is invalid because there is no such method. -Option B is invalid because there is UHTXHVW JHW$WWULEXWH ÂłSDUDPÂ´ no request instance variable.

R ! 6WULQJ S ÂżQG$WWULEXWH ÂłSDUDPÂ´ R " 6WULQJ S

-Option C is invalid because an found before checking request scope.

R # 6WULQJ S SDJH&RQWH[W ÂżQG$WWULEXWH ÂłSDUDPÂ´ attribute in page scope would be

R $ 6WULQJ S JHW3DJH&RQWH[W ÂżQG$WWULEXWH ÂłSDUDPÂ´ -Option D is invalid because

there is no getPageContext() method.

R % 6WULQJ S SDJH&RQWH[W JHW5HTXHVW JHW$WWULEXWH ÂłSDUDPÂ´

7HICH ARE VALID METHOD CALLS ON A 3DJH&RQWH[W OBJECT #HOOSE ALL THAT APPLY

(JSP v2.0 pg. 2-

23)

R ! JHW$WWULEXWH1DPHV

R " JHW$WWULEXWH ÂłNH\Â´

-Options A and D are invalid because there are no methods R # ÂżQG$WWULEXWH ÂłNH\Â´ with these names. R $ JHW6HVVLRQ$WWULEXWH

R % JHW$WWULEXWHV6FRSH ÂłNH\Â´

R & ÂżQG$WWULEXWH ÂłNH\Â´ 3DJH&RQWH[W 6(66,21B6&23( -Option F is invalid because Ă&#x17E;ndAttribute() does not R ' JHW$WWULEXWH ÂłNH\Â´ 3DJH&RQWH[W 6(66,21B6&23( have a scope parameter.

\RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN DQVZHUV

23)

(JSP v2.0 pg. 2-

7HICH IS THE MOST EFlCIENT -VS&RQWH[W METHOD TO CALL TO ACCESS AN ATTRIBUTE THAT IS KNOWN TO BE IN APPLICATION SCOPE

R ! JHW3DJH&RQWH[W -Option A is invalid because there is no such method. R " JHW$WWULEXWH 6WULQJ -Option B is invalid because this method only

looks in page scope.

R # ÂżQG$WWULEXWH 6WULQJ

-Option C is invalid because this method would be less efĂ&#x17E;cient than Option D because it Ă&#x17E;rst checks the other three scopes.

R $ JHW$WWULEXWH 6WULQJ LQW

R % JHW$WWULEXWHV6FRSH ÂłNH\Â´

-Option E is invalid because it would be only the Ă&#x17E;rst step in a process that would be much less efĂ&#x17E;cient than Option D.

R & JHW$WWULEXWH1DPHV,Q6FRSH LQW -Option F is invalid because no

such method exists.

(JSP v2.0 pg. 2-

7HAT IS THE BEST STRATEGY WHEN IMPLEMENTING A CUSTOM TAG FOR lNDING THE VALUE OF AN ATTRIBUTE WHOSE SCOPE IS UNKNOWN

R ! #HECK ALL SCOPES WITH A SINGLE SDJH&RQWH[W JHW$WWULEXWH 6WULQJ CALL

23)

-Option A is invalid because this method only checks the page scope.

R " #HECK ALL SCOPES WITH A SINGLE SDJH&RQWH[W ÂżQG$WWULEXWH 6WULQJ CALL

R # #HECK EACH SCOPE WITH CALLS TO SDJH&RQWH[W JHW$WWULEXWH 6WULQJ LQW

R $ #ALL SDJH&RQWH[W JHW5HTXHVW JHW$WWULEXWH 6WULQJ

-Options C and D are invalid because they are less efĂ&#x17E;cient than simply calling Ă&#x17E;ndAttribute().

THEN CALL SDJH&RQWH[W JHW6HVVLRQ JHW$WWULEXWH 6WULQJ

AND SO ON

R % .ONE OF THESE WILL WORK

FKDSWHU

Chapter 10. When even JSTL is not enough...

FXVWRP WDJ GHYHORSPHQW

'IVEN A TAG VLPSOH7DJ WHOSE HANDLER IS IMPLEMENTED USING THE 3IMPLE TAG MODEL AND A TAG FRPSOH[7DJ WHOSE HANDLER IS IMPLEMENTED USING THE #LASSIC TAG MODEL

(JSP v2.0 7.1.6 pg 1-156)

"OTH TAGS ARE DECLARED TO BE NON EMPTY IN THE 4,$ 7HICH *30 CODE SNIPPETS ARE VALID USES OF THESE TAG #HOOSE ALL THAT APPLY

R ! P\ VLPSOH7DJ! P\ FRPSOH[7DJ ! P\ VLPSOH7DJ!

R " P\ VLPSOH7DJ! GLVSOD\7H[W ! P\ VLPSOH7DJ!

include -Option A is correct; a Simple tag maythat tag a Complex tag in the body as long as contains no scripting code. -Option B is invalid because simple tags cannot have a body that includes a JSP expression tag.

R # P\ VLPSOH7DJ! # LQFOXGH ÂżOH Â´ :(% ,1) ZHE FRPPRQ KHDGHU0HQX KWPOÂ´ ! P\ VLPSOH7DJ!

-Option C is correct because the include directive is processed before the body of the simpleTag is converted into a JspFragment; however, the included content must also be non-scripting (which is why this example includes an HTML segment).

R $ P\ VLPSOH7DJ! P\ FRPSOH[7DJ! L ! P\ FRPSOH[7DJ! P\ VLPSOH7DJ!

-Option D is not invalid because of the complexTag usage (as in Option A), but because the complexTag body has scripting code in it.

173) (JSP v2.0 pg. 1need -Option A is invalid because tag Ă&#x17E;les locatio n only to be placed in the appropriate in order to be used. -Option B is invalid because the page directive is not available in Tag Files.

7HICH ARE TRUE ABOUT THE 4AG &ILE MODEL #HOOSE ALL THAT APPLY

R ! %ACH TAG lLE MUST HAVE A CORRESPONDING ENTRY IN A 4,$ lLE R " !LL DIRECTIVES ALLOWED IN *30 PAGES ARE ALLOWED IN 4AG &ILES

R # !LL DIRECTIVES ALLOWED IN 4AG &ILES ARE ALLOWED IN *30 PAGES

R $ 4HE MVS GR%RG\! STANDARD ACTION CAN ONLY BE

-Option C is invalid because the tag, attribute, and variable directives are not available in JSP pages.

USED IN 4AG &ILES

R % 4HE ALLOWABLE lLE EXTENSIONS FOR 4AG &ILES ARE WDJ AND WDJ[

R & &OR EACH ATTRIBUTE DECLARED AND SPECIlED IN A 4AG &ILE THE CONTAINER CREATES A PAGE SCOPED ATTRIBUTE WITH THE SAME NAME \RX DUH KHUH

Chapter 10. When even JSTL is not enough...

PRFN DQVZHUV

(JSP v2.0 pg. 1-

7HICH ARE VALID IN TAG lLES #HOOSE ALL THAT APPLY

174)

R ! MVS GR%RG\ ! R " MVS LQYRNH IUDJPHQW Â´IUDJÂ´ ! R # # SDJH LPSRUW Â´MDYD XWLO 'DWHÂ´ ! R $ # YDULDEOH QDPH JLYHQ Â´GDWHÂ´

-Option C is invalid because the page directive is not valid in tag Ă&#x17E;les.

YDULDEOH FODVV Â´MDYD XWLO 'DWHÂ´ !

R % # DWWULEXWH QDPH Â´QDPHÂ´ YDOXH Â´EODQNÂ´ -Option E is invalid because there is W\SH Â´MDYD ODQJ 6WULQJÂ´ !

no value attribute deĂ&#x17E;ned for the attribute directive.

7HICH RETURNS THE ENCLOSING TAG WHEN CALLED FROM WITHIN A TAG HANDLER CLASS #HOOSE ALL THAT APPLY

(JSP v2.0 pg. 2-

53)

R ! JHW3DUHQW

-Option A is correct; it is the only one of the methods R " JHW$QFHVWRU

shown that exists. R # ÂżQG$QFHVWRU R $ JHW(QFORVLQJ7DJ

'IVEN A WEB APPLICATION STURCUTRE

(JSP v2.0 pg. 1-

176)

:(% ,1) WDJV P\WDJV WDJ WDJ :(% ,1) WDJV WDJ WDJ :(% ,1) WDJ WDJ WDJ WDJ 7HICH TAGS COULD BE USED BY AN APPROPRIATE WDJOLE DIRECTIVE #HOOSE ALL THAT APPLY

R ! WDJ WDJ R " WDJ WDJ R # WDJ WDJ R $ WDJ WDJ

-Options C and D are invalid because tagagsĂ&#x17E;les must be placed under the /WEB-INF/tINF/tags. directory or a subdirectory of /WEB-

FKDSWHU

Chapter 11. Deploying your web app

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Chapter 11. Deploying your web app Head First Servlets and JSP By Bert Bates, Kathy Sierra, Bryan Basham ISBN: 0596005407 Publisher: O'Reilly Prepared for Stephen Goss, Safari ID: stephengoss@gmx.net Print Publication Date: 8/1/2004 User number: 747221 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited.

Chapter 11. Deploying your web app

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4HIS OBJECTIVE HAS BEEN COVERED THROUGHOUT THE BOOK IN OTHER CHAPTERS SO MOST OF THE CONTENT IN THIS CHAPTER RELATED TO THIS OBJECTIVE IS EITHER FOR REVIEW OR TO LOOK AT SOMETHING IN A LITTLE MORE DETAIL

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/BJECTIVES AND FOCUS MAINLY ON PICKY 8-, TAG DETAILS RELATED TO THE $EPLOYMENT $ESCRIPTOR 7HILE THIS IS PROBABLY THE LEAST FUN PART OF THE BOOK AND THE EXAM MOST OF THIS CONTENT IS EASY TO UNDERSTAND AND IT S JUST A MATTER OF MEMORIZING THE TAGS 4HERE IS ONE TRICKY PART THOUGH AND WE LL SPEND MOST OF OUR TIME ON ITÂ&#x2C6;SERVLET MAPPING

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7E DECIDED TO STICK THIS OBJECTIVE INTO THIS CHAPTER FOR TWO REASONS MOST OF THIS CHAPTER HAS TO DO WITH 8-, AND WE DIDN T WANT TO ADD ANYTHING ELSE INTO THE *30 CHAPTERS 7E DECIDED IT WAS BETTER FOR YOU TO CONCENTRATE MORE ON THE SYNTAX AND BEHAVIOR OF ALL THE OTHER PARTS OF *30 RATHER THAN ALSO WORRYING ABOUT THE 8-, VERSIONS OF EVERYTHING "UT NOW THAT YOU RE YOU KNOW AN EXPERT WE lGURE YOU CAN HANDLE IT

Chapter 11. Deploying your web app

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Chapter 11. Deploying your web app

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Chapter 11. Deploying your web app

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Chapter 11. Deploying your web app

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe Head First Servlets and JSP By Bert Bates, Kathy Sierra, Bryan Basham ISBN: 0596005407 Publisher:Prepared for Augusto Jaramillo Forcada, Safari ID: augustojf.cv@gmail.com O'Reilly Print Publication Date: 8/1/2004 User number: 729515 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited.

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Head First Servlets and JSP By Bert Bates, Kathy Sierra, Bryan Basham ISBN: 0596005407 Publisher:Prepared for Augusto Jaramillo Forcada, Safari ID: augustojf.cv@gmail.com O'Reilly Print Publication Date: 8/1/2004 User number: 729515 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited.

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)]\PWZQbI\QWV ;\MX " LMNQVQVO ZWTM[ 4HE MOST COMMON FORM OF AUTHORIZATION IN SERVLETS IS FOR THE CONTAINER TO DETERMINE WHETHER A SPECIl C SERVLETÂ&#x2C6;AND THE INVOKING (440 REQUEST METHODÂ&#x2C6;CAN BE CALLED BY A USER WHO HAS BEEN ASSIGNED A CERTAIN SECURITY hROLEv 3O THE l RST STEP IS TO MAP THE ROLES IN THE VENDOR SPECIl C hUSERSv l LE TO ROLES ESTABLISHED IN THE $EPLOYMENT $ESCRIPTOR

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DonĂ&#x2022;t forget that you always need the <login-conĂ&#x17E;g> element if you want to enable authentication.

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7HEN WE SAID h./"/$9v WE MEANT h.OBODY FROM /543)$% THE WEB APPv )N OTHER WORDS A CLIENT CAN T ACCESS THE CONSTRAINED RESOURCE BUT ANOTHER PART OF THE WEB APP CAN 9OU MIGHT WANT TO USE A REQUEST DISPATCHER TO FORWARD TO ANOTHER PART OF THE WEB APP BUT YOU DON T EVER WANT CLIENTS TO REQUEST THAT RESOURCE DIRECTLY 4HINK OF CONSTRAINED RESOURCES AS SORT OF LIKE PRIVATE METHODS IN A *AVA CLASSÂ&#x2C6;FOR INTERNAL USE ONLY

7HY DOES THE AUTH CONSTRAINT ELEMENT GO INSIDE SECURITY CONSTRAINT BUT ./4 INSIDE THE WEB RESOURCE COLLECTION ELEMENT

4HIS WAY YOU CAN SPECIFY A SINGLE AUTH CONSTRAINT ELEMENT WHICH COULD INCLUDE MULTIPLE ROLES AND THEN SPECIFY MULTIPLE RESOURCE COLLECTIONS FOR WHICH THE AUTH CONSTRAINT ROLE LIST APPLIES &OR EXAMPLE YOU MIGHT DEFINE AN AUTH CONSTRAINT FOR A &REQUENT "UYER ROLE AND THEN PUT WEB RESOURCE COLLECTION ELEMENTS IN FOR THE ALL THE DIFFERENT PARTS OF THE WEB APP WHERE A &REQUENT "UYER GETS SPECIAL ACCESS

$O ) ACTUALLY HAVE TO SIT THERE AND TYPE IN EVERY ONE OF MY USERS WITH THEIR PASSWORDS AND ROLES

)F YOU RE USING THE TEST MEMORY REALM FROM 4OMCAT YES "UT CHANCES ARE IN THE REAL WORLD YOU RE USING A PRODUCTION SERVER THAT GIVES YOU A HOOK INTO THE ,$!0 OR DATABASE WHERE YOUR REAL USER SECURITY INFO IS STORED

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GET2EMOTE5SER WHICH CAN BE USED TO CHECK AUTHENTICATION STATUS )T S NOT COMMONLY USED SO WE DON T COVER IT IN THIS BOOK AND THERE S NOTHING ELSE YOU NEED TO KNOW ABOUT IT FOR THE EXAM IS5SER)N2OLE WHICH WE LL LOOK AT NOW )NSTEAD OF AUTHORIZING AT THE (440 METHOD LEVEL '%4 0/34 ETC YOU CAN AUTHORIZE ACCESS TO PORTIONS OF A METHOD 4HIS GIVES YOU A WAY TO CUSTOMIZE HOW A SERVICE METHOD BEHAVES BASED ON THE USER S ROLE )F YOU RE IN THIS SERVICE METHOD DO'ET DO0OST ETC THEN THE USER MADE IT THROUGH THE DECLARATIVE AUTHORIZATION BUT NOW YOU WANT TO DO SOMETHING IN THE METHOD CONDITIONALLY BASED ON WHETHER THE USER IS IN A PARTICULAR ROLE

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<PM LMKTIZI\Q^M [QLM WN XZWOZIUUI\QK [MK]ZQ\a 4HERE S A GOOD CHANCE THAT WHEN A PROGRAMMER HARD CODES SECURITY ROLE NAMES IN A SERVLET TO USE AS THE ARGUMENT TO IS5SER)N2OLE THE PROGRAMMER WAS JUST MAKING UP A FAKE NAME (E EITHER DIDN T KNOW THE REAL ROLE NAMES OR HE S WRITING A REUSABLE COMPONENT THAT LL BE USED BY MORE THAN ONE COMPANY AND THOSE COMPANIES AREN T LIKELY TO HAVE THE EXACT ROLE NAMES THE PROGRAMMER USED /F COURSE IF THE PROGRAMMER REALLY WANTS TO BUILD REUSABLE COMPONENTS HARD CODING A ROLE NAME IS A 4ERRIBLE )DEA BUT WE LL SUSPEND DISBELIEF FOR NOW )T TURNS OUT THAT THE $EPLOYMENT $ESCRIPTOR HAS A MECHANISM FOR MAPPING HARD CODED WHICH MEANS

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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3O IS (4403 OVER 33, JUST BUILT IN TO THE #ONTAINER SOMEHOW

)T S NOT GUARANTEED BY THE SPEC BUT IT S EXTREMELY LIKELY THAT YOUR #ONTAINER IS USING (4403 OVER 33, SECURE SOCKETS "UT IT WON T NECESSARILY BE AUTOMATIC 9OU PROBABLY HAVE TO CONFIGURE 33, IN YOUR #ONTAINER AND MORE IMPORTANTLYÂ&#x2C6;YOU NEED A CERTIFICATE 9OU LL HAVE TO CHECK YOUR #ONTAINER S DOCU MENTATION BUT CHANCES ARE YOUR #ONTAINER CAN GENERATE A CERTIFICATE THAT YOU CAN USE FOR TESTING BUT FOR PRODUCTION YOU LL NEED TO GET A 0UBLIC +EY CERTIFICATION FROM AN hOFFICIALv SOURCE SUCH AS 6ERI3IGN #ERTIFICATES AND SECURITY PROTOCOLS LIKE (4403 AND 33, ARE WAY OUTSIDE THE SCOPE OF THE EXAM BY THE WAY 9OU RE EXPECTED TO KNOW ONLY WHAT YOU HAVE TO DO IN THE $$ AND WHY 9OU RE NOT EXPECTED TO BE THE SYS ADMIN AND NETWORK SECURITY MASTER

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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Chapter 12. Keep it secret, keep it safe

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ap 12 )

(servlet spec: ch

-Option A is correct. Authorization operates completely within the container oncentication can authentication has occurred. Authe how the affect the transport layer based on <auth-method> element is set.

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-Option A is correct. The existence of anes empty <auth-constraint> element overrid all other <auth-constraint> elements that refer to that resource, precluding access.

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Chapter 12. Keep it secret, keep it safe

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-Option D is correct. This would typically be accomplished through the use of HTTPS.

7HICH ARE REQUIRED lELDS IN THE LOGIN FORM WHEN USING &ORM "ASED !UTHENTICATION #HOOSE ALL THAT APPLY

R ! SZ R " LG R # MBSZ R $ MBLG R % SDVVZRUG R & MBSDVVZRUG

must be -Option F is correct, the userĂ&#x2022;s password addition, the stored in a Ă&#x17E;eld called j_password. Iname. userĂ&#x2022;s name must be stored in j_usern

7HICH AUTHENTICATION TYPES REQUIRE A SPECIlC TYPE OF (4-, ACTION #HOOSE ALL THAT APPLY

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-Option B is correct. For form based the authentication to work, the action of login form must be j_security_check.

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-Option A is correct. The isUserInRole method can be used programatically, to help determine whether a clientĂ&#x2022;s role is authorized to access a given resource. -Option C is correct. The getRemoteUser method can be used programatically, to help determine whether a client has been authenticated.

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-Option D is correct. A <transport-guarantee> element is used within a <user-data-constraint> element to specify whether a web resource collection should be transmitted using a mechanism such as SSL.

7HICH AUTHENTICATION MECHANISM IS RECOMMENDED TO BE USED ONLY IF COOKIES OR 33, SESSION TRACKING IS IN PLACE

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Chapter 13. The Power of Filters

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Chapter 13. The Power of Filters Head First Servlets and JSP By Bert Bates, Kathy Sierra, Bryan Basham ISBN: 0596005407 Publisher:Prepared for Augusto Jaramillo Forcada, Safari ID: augustojf.cv@gmail.com O'Reilly Print Publication Date: 8/1/2004 User number: 729515 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited.

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Chapter 13. The Power of Filters

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0W_ IJW]\ [WUM SQVL WN ÂšNQT\MZÂş' &ILTERS ARE *AVA COMPONENTSÂ&#x2C6;VERY SIMILAR TO SERVLETSÂ&#x2C6;THAT YOU CAN USE TO INTERCEPT AND PROCESS REQUESTS BEFORE THEY ARE SENT TO THE SERVLET OR TO PROCESS RESPONSES AFTER THE SERVLET HAS COMPLETED BUT BEFORE THE RESPONSE GOES BACK TO THE CLIENT 4HE #ONTAINER DECIDES WHEN TO INVOKE YOUR l LTERS BASED ON DECLARATIONS IN THE $$ )N THE $$ THE DEPLOYER MAPS WHICH l LTERS WILL BE CALLED FOR WHICH REQUEST 52, PATTERNS 3O IT S THE DEPLOYER NOT THE PROGRAMMER WHO DECIDES WHICH SUBSET OF REQUESTS OR RESPONSES SHOULD BE PROCESSED BY WHICH l LTERS

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Chapter 13. The Power of Filters

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Chapter 13. The Power of Filters

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*]QTLQVO \PM ZMY]M[\ \ZIKSQVO N QT\MZ /UR TASK IS TO ENHANCE THE "EER APPLICATION SO THAT WHENEVER SOMEONE REQUESTS ANY OF THE RESOURCES ASSOCIATED WITH UPDATING RECIPES WE LL BE ABLE TO KEEP TRACK OF WHO MADE THE REQUEST (ERE S ONE VERSION OF WHAT SUCH A l LTER MIGHT LOOK LIKE

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Every Ă&#x17E;lter MUST implement the Filter interface.

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This is how the next Ă&#x17E;lter or servlet in line gets called - lots more on this in the next couple of pages.

You must implement destroy() but usually itĂ&#x2022;s empty. \RX DUH KHUH

Chapter 13. The Power of Filters

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7HEN THE #ONTAINER DECIDES TO INSTANTIATE A lLTER THE INIT METHOD IS YOUR CHANCE TO DO ANY SET UP TASKS BEFORE THE lLTER IS CALLED 4HE MOST COMMON IMPLEMENTATION WAS SHOWN ON THE PREVIOUS PAGE SAVING A REFERENCE TO THE &ILTER#ONlG OBJECT FOR LATER USE IN THE lLTER

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4HE DO&ILTER METHOD OF THE &ILTER#HAIN TAKES CARE OF FIGURING OUT WHOSE DO&ILTER METHOD TO INVOKE NEXT OR IF IT S THE END OF THE CHAIN WHICH SERVLET S SERVICE METHOD BUT THE DO&ILTER METHOD IN A &ILTER ACTUALLY DOES THE FILTERINGÂ&#x2C6;THE THING THE FILTER WAS CREATED TO DO 4HIS MEANS A &ILTER#HAIN CAN INVOKE %)4(%2 A FILTER OR A SERVLET DEPENDING ON WHETHER IT S THE END OF THE CHAIN 4HE END OF THE CHAIN IS ALWAYS EITHER A SERVLET OR A *30 WHICH MEANS A *30 S GENERATED SERVLET OF COURSE ASSUMING THE #ONTAINER IS ABLE TO MAP THE REQUEST 52, TO A SERVLET OR *30 )F THE #ONTAINER CAN T LOCATE THE RIGHT RESOURCE FOR THE REQUEST THE FILTER IS NEVER INVOKED

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?M KIV QUXTMUMV\ W]Z 7?6 ZM[XWV[M 4HE #ONTAINER ALREADY IMPLEMENTS THE (TTP3ERVLET2ESPONSE INTERFACE THAT S WHAT YOU GET IN THE DO&ILTER AND SERVICE METHODS "UT TO GET THIS COMPRESSION l LTER WORKING WE HAVE TO MAKE OUR OWN CUSTOM IMPLEMENTATION OF THE (TTP3ERVLET2ESPONSE INTERFACE AND PASS THAT TO THE SERVLET VIA THE CHAIN DO&ILTER CALL !ND THAT CUSTOM IMPLEMENTATION HAS TO ALSO INCLUDE A CUSTOM OUTPUT STREAM AS WELL SINCE THAT S THE GOALÂ&#x2C6;TO CAPTURE THE OUTPUT AFTER THE SERVLET WRITES TO IT BUT BEFORE IT GOES BACK TO THE CLIENT

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Chapter 13. The Power of Filters

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"UT FORTUNATELY SOMEONE AT 3UN DID THAT FOR YOU BY CREATING A SUPPORT CONVENIENCE CLASS THAT IMPLEMENTS THE (TTP3ERVLET2ESPONSE INTERFACE !LL OF THE METHODS IN THAT CLASS DELEGATE THE CALLS TO THE UNDERLYING REAL RESPONSE CREATED BY THE #ONTAINER

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Chapter 13. The Power of Filters

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?ZIXXMZ[ ZWKS 4HE WRAPPER CLASSES IN THE SERVLET !0) ARE AWESOMEÂ&#x2C6;THEY IMPLEMENT ALL THE METHODS NEEDED FOR THE THING YOU RE TRYING TO WRAP DELEGATING ALL CALLS TO THE UNDERLYING REQUEST OR RESPONSE OBJECT !LL YOU NEED TO DO IS EXTEND ONE OF THE WRAPPERS AND OVERRIDE JUST THE METHODS YOU NEED TO DO YOUR CUSTOM WORK 9OU VE SEEN SUPPORT CLASSES IN THE * 3% !0) OF COURSE WITH THINGS LIKE THE ,ISTENER ADAPTER CLASSES FOR '5)S !ND YOU VE SEEN THEM IN THE *30 !0) WITH THE CUSTOM TAG SUPPORT CLASSES "UT WHILE THOSE SUPPORT CLASSES AND THESE REQUEST AND RESPONSE WRAPPERS ARE ALL CONVENIENCE CLASSES THE WRAPPERS ARE A LITTLE DIFFERENT BECAUSE THEY WELL WRAP AN OBJECT OF THE TYPE THEY IMPLEMENT )N OTHER WORDS THEY DON T JUST PROVIDE AN INTERFACE IMPLEMENTATION THEY ACTUALLY HOLD A REFERENCE TO AN OBJECT OF THE SAME INTERFACE TYPE TO WHICH THEY DELEGATE METHOD CALLS "Y THE WAY THIS HAS NOTHING WHATSOEVER TO DO WITH THE * 3% hPRIMITIVE WRAPPERv CLASSES LIKE )NTEGER "OOLEAN $OUBLE ETC #REATING A SPECIALIZED VERSION OF A REQUEST OR RESPONSE IS SUCH A COMMON APPROACH WHEN CREATING l LTERS THAT 3UN HAS CREATED FOUR hCONVENIENCEv CLASSES TO MAKE THE JOB EASIER

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WrappER (your custom response object)

WrappEE (the original Container-created response object)

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Chapter 13. The Power of Filters

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)LLQVO I [QUXTM ?ZIXXMZ \W \PM LM[QOV ,ET S ENHANCE 2ACHEL S l RST PSEUDO CODE BY ADDING A WRAPPER

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this LetĂ&#x2022;s subclass fo r our wrapper class es... own evil purpos

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The act of Ă&#x2019;wrappingĂ&#x201C; the response with our custom Wrapper class.

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Now we send this along down the Ă&#x17E;lter chain. None of the components down the chain will ever know that the response object they got was a custom job.

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Chapter 13. The Power of Filters

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)LL IV W]\X]\ [\ZMIU ?ZIXXMZ ,ET S ADD A SECOND 7RAPPER

thod to return Override this me stream. ut tp ou om a cust

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UHWXUQ VHUYOHW*]LS26 ` urn a Ă&#x2019;specialĂ&#x201C;

Ret ServletOutputStream to whoever asks for one.

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Ă&#x2019;WrappingĂ&#x201C; the ServletOutputStream with our custom ServletOutputStream Wrapper class. For now letĂ&#x2022;s assume Gzip ServletOutputStream extends ServletOutputStream.

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Chapter 13. The Power of Filters

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<PM ZMIT KWUXZM[[QWV NQT\MZ KWLM 4IME TO CODE 7E END THIS CHAPTER BY LOOKING AT THE CODE FOR BOTH THE COMPRESSION l LTER AND THE WRAPPER IT USES 7E RE EXPANDING FROM THE PREVIOUS DISCUSSION AND WHILE THERE IS SOME NEW STUFF HERE IT S MOSTLY JUST PLAIN *AVA CODE 4HIS FILTER PROVIDES A MECHANISM TO COMPRESS THE RESPONSE BODY CONTENT 4HIS TYPE OF l LTER WOULD COMMONLY BE APPLIED TO ANY TEXT CONTENT SUCH AS (4-, BUT NOT TO MOST MEDIA FORMATS SUCH AS 0.' OR -0%' BECAUSE THEY ARE ALREADY COMPRESSED SDFNDJH FRP H[DPSOH ZHE LPSRUW MDYD[ VHUYOHW LPSRUW MDYD[ VHUYOHW KWWS LPSRUW MDYD LR LPSRUW MDYD XWLO ]LS *=,32XWSXW6WUHDP

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The init method saves the conĂ&#x17E;g object to the servlet

and a quick reference SXEOLF YRLG LQLW )LOWHU&RQÂż J FIJ context object (for logging purposes). WKURZV 6HUYOHW([FHSWLRQ ^ WKLV FIJ FIJ FW[ FIJ JHW6HUYOHW&RQWH[W FW[ ORJ FIJ JHW)LOWHU1DPH Âł LQLWLDOL]HG Â´ The heart of this Ă&#x17E;lter wraps `

the response object with a Decorator that wraps the output stream with a compression I/O stream. Compression of the output stream is performed

SXEOLF YRLG GR)LOWHU 6HUYOHW5HTXHVW UHT if and only if the client includes an Accept 6HUYOHW5HVSRQVH UHVS Encoding header (speciĂ&#x17E;cally, for gzip). )LOWHU&KDLQ IF

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Does the client accept GZIP compression?

If so, wrap the response object with a compression wrapper.

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Chapter 13. The Power of Filters

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+WUXZM[[QWV NQT\MZ KWLM KWV\

'HEXJJLQJ 7LS 4O TEST THIS l LTER COMMENT OUT THIS LINE OF CODE 9OU SHOULD SEE ILLEGIBLE COMPRESSED DATA IN YOUR BROWSER

response Declare that theGZ IP encoded. content is being

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Chain to the next component.

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A GZIP compression stream must be Ă&#x2019;Ă&#x17E;nishedĂ&#x201C;, which also Ă&#x;ushes the GZIP stream buffer, and sends all of its data to the original response stream. The container handles the rest of the work.

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/NE OF THE HEADERS THAT THE BROWSER SENDS h!CCEPT %NCODING GZIPv TELLS THE SERVER ABOUT THE BROWSER S CAPABILITIES FOR DEALING WITH DIFFERENT TYPES OF CONTENT )F THE SERVER SEES THAT THE BROWSER CAN DEAL WITH COMPRESSED DATA IT WILL PERFORM THE COMPRESSION AND ADD A HEADER h#ONTENT %NCODING GZIPv TO THE RESPONSE 7HEN THE BROWSER RECEIVES THE RESPONSE THE h#ONTENT %NCODING GZIPv HEADER TELLS THE BROWSER TO DE COMPRESS THE DATA BEFORE IT IS DISPLAYED \RX DUH KHUH

Chapter 13. The Power of Filters

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+WUXZM[[QWV _ZIXXMZ KWLM 7E LOOKED AT THE #OMPRESSION l LTER NOW LET S TAKE A LOOK AT THE WRAPPER IT USES 4HIS IS ONE OF THE MOST COMPLICATED TOPICS IN ALL OF SERVLET DOM SO DON T PANIC IF YOU DON T GROK IT THE l RST TIME 4HIS RESPONSE WRAPPER DECORATES THE ORIGINAL RESPONSE OBJECT BY ADDING A COMPRESSION DECORATOR ON THE ORIGINAL SERVLET OUTPUT STREAM SDFNDJH FRP H[DPSOH ZHE 6HUYOHW LPSRUWV LPSRUW MDYD[ VHUYOHW KWWS LPSRUW MDYD[ VHUYOHW , 2 LPSRUWV LPSRUW MDYD LR LPSRUW MDYD XWLO ]LS *=,32XWSXW6WUHDP FODVV &RPSUHVVLRQ5HVSRQVH:UDSSHU H[WHQGV +WWS6HUYOHW5HVSRQVH:UDSSHU ^

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The compressed output stream for the servlet response.

The PrintWriter object to the compressed output stream.

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The super constructor performs the Decorator responsibility of storing a reference to the object being decorated, in this case the HTTP response object.

Ignore this methodĂ&#x2018;the output will be compressed.

This decorator method, used by the Ă&#x17E;lter, gives the compression Ă&#x17E;lter a handle on the GZIP output stream so that the Ă&#x17E;lter can Ă&#x2019;Ă&#x17E;nishĂ&#x201C; and Ă&#x;ush the GZIP stream.

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Chapter 13. The Power of Filters

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+WUXZM[[QWV _ZIXXMZ KWLM KWV\ Provide access to a decorated servlet output stream.

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Wrap the original servlet output VWUHDP8VHG VHUYOHW*]LS26 stream with our compression ` servlet output stream. UHWXUQ VHUYOHW*]LS26 ` decorated

Provide access to a print writer.

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To make a print writer, we have JHW2XWSXW6WUHDP

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Chapter 13. The Power of Filters

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*=,32XWSXW6WUHDP LQWHUQDO*]LS26

Keep a reference to the raw GZIP stream. This instance variable is package-private to allow the compression response wrapper access to this variable..

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This method implements the compression decoration by delegating the write() call to the GZIP compression stream, which is wrapping the original ServletOutputStream, (which in turn is ultimately wrapping the TCP network output stream to the client).

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Chapter 13. The Power of Filters

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Chapter 13. The Power of Filters

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7HICH ARE TRUE ABOUT lLTERS #HOOSE ALL THAT APPLY

R ! ! lLTER CAN ACT ON ONLY THE REQUEST OR RESPONSE OBJECT NOT BOTH

R " 4HE GHVWUR\ METHOD IS ALWAYS A CONTAINER CALLBACK METHOD

R # 4HE GR)LOWHU METHOD IS ALWAYS A CONTAINER CALLBACK METHOD

R $ 4HE ONLY WAY A lLTER CAN BE INVOKED IS THROUGH A DECLARATION IN THE $$

R % 4HE NEXT lLTER IN A lLTER CHAIN CAN BE SPECIlED EITHER BY THE PREVIOUS lLTER OR IN THE $$

7HICH ARE TRUE ABOUT DECLARING lLTERS IN THE $$ #HOOSE ALL THAT APPLY

R ! 5NLIKE SERVLETS lLTERS #!../4 DECLARE INITIALIZATION PARAMETERS R " &ILTER CHAIN ORDER IS ALWAYS DETERMINED BY THE ORDER THE ELEMENTS APPEAR IN THE $$

R # ! CLASS THAT EXTENDS AN !0) REQUEST OR RESPONSE WRAPPER CLASS MUST BE DECLARED IN THE $$

R $ ! CLASS THAT EXTENDS AN !0) REQUEST OR RESPONSE WRAPPER CLASS IS USING THE )NTERCEPTING &ILTER PATTERN

R % &ILTER CHAIN ORDER IS AFFECTED BY WHETHER lLTER MAPPINGS ARE DECLARED VIA XUO SDWWHUQ! OR VIA VHUYOHW QDPH!

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Chapter 13. The Power of Filters

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'IVEN THIS METHOD IN AN OTHERWISE PROPERLY DElNED )LOWHU IMPLEMENTATION SXEOLF YRLG GR)LOWHU 6HUYOHW5HTXHVW UHT 6HUYOHW5HVSRQVH UHVSRQVH )LOWHU&KDLQ FKDLQ WKURZV ,2([FHSWLRQ 6HUYOHW([FHSWLRQ ^ +WWS6HUYOHW5HTXHVW UHTXHVW +WWS6HUYOHW5HTXHVW UHT +WWS6HVVLRQ VHVVLRQ UHTXHVW JHW6HVVLRQ 2EMHFW XVHU VHVVLRQ JHW$WWULEXWH Â³XVHUÂ´ LI XVHU QXOO ^ 8VHU5HTXHVW XUHT QHZ 8VHU5HTXHVW UHTXHVW XVHU FKDLQ GR)LOWHU XUHT UHVSRQVH ` HOVH ^ 5HTXHVW'LVSDWFKHU UG UHTXHVW JHW5HTXHVW'LVSDWFKHU Â³ ORJLQ MVSÂ´ UG IRUZDUG UHTXHVW UHVSRQVH ` ` 7HICH IS TRUE

R ! !N EXCEPTION WILL ALWAYS BE THROWN IF LINE EXECUTES R " ,INE IS INVALID BECAUSE UHTXHVW MUST BE PASSED AS THE lRST ARGUMENT

R # 4HIS LINE FKDLQ GR)LOWHU UHTXHVW UHVSRQVH MUST BE INSERTED SOMEWHERE IN THE HOVH BLOCK

R $ 4HIS METHOD DOES NOT PROPERLY IMPLEMENT )LOWHU GR)LOWHU BECAUSE THE METHOD SIGNATURE IS INCORRECT

R % .ONE OF THE ABOVE

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Chapter 13. The Power of Filters

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'IVEN A PARTIAL DEPLOYMENT DESCRIPTOR Â¿OWHU! Â¿OWHU QDPH!0\ )LOWHU Â¿OWHU QDPH! Â¿OWHU FODVV!FRP H[DPSOH 0\)LOWHU Â¿OWHU FODVV! Â¿OWHU! Â¿OWHU PDSSLQJ! Â¿OWHU QDPH!0\ )LOWHU Â¿OWHU QDPH! XUO SDWWHUQ! P\ XUO SDWWHUQ! Â¿OWHU PDSSLQJ! VHUYOHW! VHUYOHW QDPH!0\ 6HUYOHW VHUYOHW QDPH! VHUYOHW FODVV!FRP H[DPSOH 0\6HUYOHW VHUYOHW FODVV! VHUYOHW! VHUYOHW PDSSLQJ! VHUYOHW QDPH!0\ 6HUYOHW VHUYOHW QDPH! XUO SDWWHUQ! P\ XUO SDWWHUQ! VHUYOHW PDSSLQJ! 7HICH IS TRUE #HOOSE ALL THAT APPLY

R ! 4HE lLE IS INVALID BECAUSE THE 52, PATTERN P\ IS MAPPED TO BOTH A SERVLET AND A lLTER

R " 4HE lLE IS INVALID BECAUSE NEITHER THE SERVLET NAME NOR THE lLTER NAME IS ALLOWED TO CONTAIN SPACES

R # 4HE lLTER 0\)LOWHU WILL BE INVOKED AFTER THE 0\6HUYOHW SERVLET FOR EACH REQUEST THAT MATCHES THE PATTERN P\

R $ 4HE lLTER 0\)LOWHU WILL BE INVOKED BEFORE THE 0\6HUYOHW SERVLET FOR EACH REQUEST THAT MATCHES THE PATTERN P\

R % 4HE lLE IS INVALID BECAUSE THE Â¿OWHU! ELEMENT MUST CONTAIN A VHUYOHW QDPH! ELEMENT THAT DElNES WHICH SERVLET THE lLTER SHOULD BE APPLIED TO

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Chapter 13. The Power of Filters

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7HICH ABOUT lLTERS ARE TRUE #HOOSE ALL THAT APPLY

R ! &ILTERS MAY BE USED TO CREATE REQUEST OR RESPONSE WRAPPERS R " 7RAPPERS MAY BE USED TO CREATE REQUEST OR RESPONSE lLTERS R # 5NLIKE SERVLETS ALL lLTER INITIALIZATION CODE SHOULD BE PLACED IN THE CONSTRUCTOR SINCE THERE IS NO LQLW METHOD

R $ &ILTERS SUPPORT AN INITIALIZATION MECHANISM THAT INCLUDES AN LQLW METHOD THAT IS GUARANTEED TO BE CALLED BEFORE THE lLTER IS USED TO HANDLE REQUESTS

R % ! lLTER S GR)LOWHU METHOD MUST CALL GR)LOWHU ON THE INPUT )LOWHU&KDLQ OBJECT IN ORDER TO ENSURE THAT ALL lLTERS HAVE A CHANCE TO EXECUTE

R & 7HEN CALLING GR)LOWHU ON THE INPUT )LOWHU&KDLQ A lLTER S GR)LOWHU METHOD MUST PASS IN THE SAME 6HUYOHW5HTXHVW AND 6HUYOHW5HVSRQVH OBJECTS THAT WERE PASSED INTO IT

R ' ! lLTER S GR)LOWHU MAY BLOCK FURTHER REQUEST PROCESSING

7HICH ARE TRUE ABOUT THE SERVLET 7RAPPER CLASSES #HOOSE ALL THAT APPLY

R ! 4HEY PROVIDE THE ONLY MECHANISM FOR WRAPPING 6HUYOHW5HVSRQVH OBJECTS

R " 4HEY CAN BE USED TO DECORATE CLASSES THAT IMPLEMENT )LOWHU

R # 4HEY CAN BE USED EVEN WHEN THE APPLICATION DOES ./4 SUPPRT (440

R $ 4HE !0) PROVIDES WRAPPERS FOR 6HUYOHW5HTXHVW 6HUYOHW5HVSRQVH AND )LOWHU&KDLQ OBJECTS

R % 4HEY IMPLEMENT THE )NTERCEPTING &ILTER PATTERN R & 7HEN YOU SUBCLASS A WRAPPER CLASS YOU MUST OVERRIDE AT LEAST ONE OF THE WRAPPER CLASS S METHODS

\RX DUH KHUH

Chapter 13. The Power of Filters

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7HICH ARE TRUE ABOUT lLTERS #HOOSE ALL THAT APPLY

R ! ! lLTER CAN ACT ON ONLY THE REQUEST OR RESPONSE OBJECT

NOT BOTH

R " 4HE GHVWUR\ METHOD IS ALWAYS A CONTAINER CALLBACK METHOD

R # 4HE GR)LOWHU METHOD IS ALWAYS A CONTAINER CALLBACK -Option C is incorrect, doFilter is both METHOD

a callback and an inline method.

R $ 4HE ONLY WAY A lLTER CAN BE INVOKED IS THROUGH A DECLARATION IN THE $$

rect, the order

E is incor R % 4HE NEXT lLTER IN A lLTER CHAIN CAN BE SPECIlED EITHER -Optionter execution is always BY THE PREVIOUS lLTER OR IN THE $$

of Ă&#x17E;l . determined in the DD

7HICH ARE TRUE ABOUT DECLARING lLTERS IN THE $$ #HOOSE ALL THAT APPLY

R ! 5NLIKE SERVLETS lLTERS #!../4 DECLARE INITIALIZATION PARAMETERS R " &ILTER CHAIN ORDER IS ALWAYS DETERMINED BY THE ORDER THE ELEMENTS APPEAR IN THE $$

R # ! CLASS THAT EXTENDS AN !0) REQUEST OR RESPONSE WRAPPER CLASS MUST BE DECLARED IN THE $$

R $ ! CLASS THAT EXTENDS AN !0) REQUEST OR RESPONSE WRAPPER CLASS IS USING THE )NTERCEPTING &ILTER PATTERN

R % &ILTER CHAIN ORDER IS AFFECTED BY WHETHER lLTER MAPPINGS ARE

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-Option B is incorrect, because <url-pattern> mappings will be chained before <servlet-name> mappings. -Option D is incorrect, wrappers are examples of the Decorator pattern.

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Chapter 13. The Power of Filters

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R ! !N EXCEPTION WILL ALWAYS BE THROWN IF LINE EXECUTES R " ,INE IS INVALID BECAUSE UHTXHVW MUST BE PASSED AS THE lRST ARGUMENT

ect as quest. A is incorrrw -Option lt fo ard a re to er Ă&#x17E; a for

-Option B is incorrect because it is valid for a Ă&#x17E;lter to wrap a request (note that UserRequest must implement ServletRequest).

R # 4HIS LINE FKDLQ GR)LOWHU UHTXHVW UHVSRQVH -Option C is incorrect because the MUST BE INSERTED SOMEWHERE IN THE HOVH BLOCK

R $ 4HIS METHOD DOES NOT PROPERLY IMPLEMENT )LOWHU GR)LOWHU BECAUSE THE METHOD SIGNATURE IS INCORRECT

doFilter method is NOT required to call chain.doFilter().

-Option D is incorrect because the method signature is correct.

R % .ONE OF THE ABOVE

\RX DUH KHUH

Chapter 13. The Power of Filters

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A is incorrect because this is R ! 4HE lLE IS INVALID BECAUSE THE 52, PATTERN P\ -Option syntax used to map a Ă&#x17E;lter to proper IS MAPPED TO BOTH A SERVLET AND A lLTER

the same pattern as a servlet.

R " 4HE lLE IS INVALID BECAUSE NEITHER THE SERVLET NAME -Option B is incorrect because NOR THE lLTER NAME IS ALLOWED TO CONTAIN SPACES

R # 4HE lLTER 0\)LOWHU WILL BE INVOKED AFTER THE 0\6HUYOHW SERVLET FOR EACH REQUEST THAT MATCHES THE PATTERN P\

there is no such restriction.

-Option C is incorrect because Ă&#x17E;lters are executed before servlets, not after.

R $ 4HE lLTER 0\)LOWHU WILL BE INVOKED BEFORE THE 0\6HUYOHW SERVLET FOR EACH REQUEST THAT MATCHES THE PATTERN P\

R % 4HE lLE IS INVALID BECAUSE THE ÂżOWHU! ELEMENT MUST -Option E is incorrect because CONTAIN A VHUYOHW QDPH! ELEMENT THAT DElNES WHICH SERVLET THE lLTER SHOULD BE APPLIED TO

either a <servlet-name> element or a <url-pattern> may be used within a <Ă&#x17E;lter-mapping> element.

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Chapter 13. The Power of Filters

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7HICH ABOUT lLTERS ARE TRUE #HOOSE ALL THAT APPLY

R ! &ILTERS MAY BE USED TO CREATE REQUEST OR RESPONSE WRAPPERS -Option B is incorrect because R " 7RAPPERS MAY BE USED TO CREATE REQUEST OR RESPONSE lLTERS the terminology is reversed. R # 5NLIKE SERVLETS ALL lLTER INITIALIZATION CODE SHOULD BE PLACED IN

-Option C is incorrect because there is an init() method that should be used for Ă&#x17E;lter initialization.

THE CONSTRUCTOR SINCE THERE IS NO LQLW METHOD

R $ &ILTERS SUPPORT AN INITIALIZATION MECHANISM THAT INCLUDES AN LQLW METHOD THAT IS GUARANTEED TO BE CALLED BEFORE THE lLTER IS USED TO HANDLE REQUESTS

R % ! lLTER S GR)LOWHU METHOD MUST CALL GR)LOWHU ON THE -Option E is incorrect because INPUT )LOWHU&KDLQ OBJECT IN ORDER TO ENSURE THAT ALL lLTERS HAVE A CHANCE TO EXECUTE

R & 7HEN CALLING GR)LOWHU ON THE INPUT )LOWHU&KDLQ A lLTER S GR)LOWHU METHOD MUST PASS IN THE SAME 6HUYOHW5HTXHVW AND 6HUYOHW5HVSRQVH OBJECTS THAT WERE PASSED INTO IT

R ' ! lLTER S GR)LOWHU MAY BLOCK FURTHER REQUEST PROCESSING

calling doFilter() is not necessary if a Ă&#x17E;lter wishes to block further request processing.

-Option F is incorrect because the Ă&#x17E;lter may choose to Ă&#x2019;wrapĂ&#x201C; the request or the response object and pass those instead.

7HICH ARE TRUE ABOUT THE SERVLET 7RAPPER CLASSES #HOOSE ALL THAT APPLY

(API)

-Option A is incorrect because you can create your own wrapper class.

R ! 4HEY PROVIDE THE ONLY MECHANISM FOR WRAPPING 6HUYOHW5HVSRQVH OBJECTS

R " 4HEY CAN BE USED TO DECORATE CLASSES THAT IMPLEMENT -Option B is incorrect because these classes

are used to wrap requests and responses.

)LOWHU

R # 4HEY CAN BE USED EVEN WHEN THE APPLICATION DOES ./4 SUPPRT (440

R $ 4HE !0) PROVIDES WRAPPERS FOR 6HUYOHW5HTXHVW -Option D is incorrect because the API r. 6HUYOHW5HVSRQVH AND )LOWHU&KDLQ OBJECTS

does NOT provide a FilterChain wrappe

R % 4HEY IMPLEMENT THE )NTERCEPTING &ILTER PATTERN -Option E is incorrect because these wrappers

implement the Decorator pattern..

R & 7HEN YOU SUBCLASS A WRAPPER CLASS YOU MUST OVERRIDE AT LEAST ONE OF THE WRAPPER CLASS S METHODS

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Chapter 14. Enterprise Design Patterns

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Chapter 14. Enterprise Design Patterns Head First Servlets and JSP By Bert Bates, Kathy Sierra, Bryan Basham ISBN: 0596005407 Publisher:Prepared for Augusto Jaramillo Forcada, Safari ID: augustojf.cv@gmail.com O'Reilly Print Publication Date: 8/1/2004 User number: 729515 Copyright 2007, Safari Books Online, LLC. This PDF is exclusively for your use in accordance with the Safari Terms of Service. No part of it may be reproduced or transmitted in any form by any means without the prior written permission for reprints and excerpts from the publisher. Redistribution or other use that violates the fair use priviledge under U.S. copyright laws (see 17 USC107) or that otherwise violates the Safari Terms of Service is strictly prohibited.

Chapter 14. Enterprise Design Patterns

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4HE OBJECTIVES IN THIS SECTION ARE COVERED COMPLETELY IN THIS CHAPTER .O MAKE THAT -/2% THAN COMPLETELY 4HE EXAM QUESTIONS ON PATTERNS ARE THE LEAST TRICKY OF ALL THE POSSIBLE QUESTIONS YOU LL SEE ON THE EXAM SO YOU CAN ALMOST RELAX IN THIS SECTION )F YOU RE ALREADY FAMILIAR WITH THE FUNDAMENTAL ENTERPRISE DESIGN PATTERNS YOU CAN PROBABLY ANSWER THE EXAM QUESTIONS ON PATTERNS

!ND ALTHOUGH 3TRUTS IS NOT ON THE EXAM THIS CHAPTER ALSO INCLUDES AN INTRODUCTION TO 3TRUTS CURRENTLY THE MOST COMMONLY USED FRAMEWORK FOR AN -6# WEB APPLICATION

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Chapter 14. Enterprise Design Patterns

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?MJ [Q\M PIZL_IZM KIV OM\ KWUXTQKI\ML )N THE 2EAL 7ORLD WEB APPS CAN GET COMPLICATED ! POPULAR WEB SITE CAN GET HUNDREDS OF THOUSANDS OF HITS PER DAY 4O HANDLE THIS KIND OF VOLUME MOST BIG WEB SITES CREATE COMPLEX HARDWARE ARCHITECTURES IN WHICH THE SOFTWARE AND DATA IS DISTRIBUTED ACROSS MANY MACHINES ! COMMON ARCHITECTURE YOU RE PROBABLY QUITE FAMILIAR WITH IS CONl GURING THE HARDWARE IN LAYERS OR hTIERSv OF FUNCTIONALITY !DDING MORE COMPUTERS TO A TIER IS KNOWN AS HORIZONTAL SCALING AND IS CONSIDERED ONE OF THE BEST WAYS TO INCREASE THROUGHPUT :HE EURZVHU

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Chapter 14. Enterprise Design Patterns

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?MJ IXXTQKI\QWV [WN\ _IZM KIV OM\ KWUXTQKI\ML !S WE VE SEEN IT S VERY COMMON FOR A WEB APPLICATION TO BE MADE UP OF MANY DIFFERENT KINDS OF SOFTWARE COMPONENTS 4HE WEB TIER FREQUENTLY CONTAINS (4-, PAGES *30S SERVLETS CONTROLLERS MODEL COMPONENTS IMAGES AND SO ON 4HE BUSINESS TIER CAN CONTAIN %*"S LEGACY APPLICATIONS LOOKUP REGISTRIES AND IN MOST CASES DATABASE DRIVERS AND DATABASES

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Chapter 14. Enterprise Design Patterns

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4]KSa NWZ ][ _M PI^M 2 -- XI\\MZV[ 4HE GOOD NEWS IS THAT A LOT OF PEOPLE HAVE BEEN USING * %% CONTAINERS TO SOLVE THE VERY SAME PROBLEMS YOU RE LIKELY TO ENCOUNTER 4HEY FOUND REOCCURING THEMES IN THE NATURE OF THE PROBLEMS THEY WERE DEALING WITH AND THEY CAME UP WITH REUSABLE SOLUTIONS TO THESE PROBLEMS 4HESE DESIGN PATTERNS HAVE BEEN USED TESTED AND RElNED BY OTHER DEVELOPERS SO YOU DON T HAVE TO REINVENT THE WHEEL

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4HE MOST IMPORTANT JOB FOR A WEB APP IS TO PROVIDE THE END USER WITH A RELIABLE USEFUL AND CORRECT EXPERIENCE )N OTHER WORDS THE PROGRAM MUST SATISFY THE FUNCTIONAL REQUIREMENTS SUCH AS hSELECT A BEER STYLEv OR hADD MALT TO MY SHOPPING CARTv /NCE YOU VE MADE SURE THAT THE SYSTEM SUPPORTS THE USE CASES YOU LL MOST LIKELY BE FACED WITH ANOTHER SET OF REQUIREMENTSÂ&#x2C6;REQUIREMENTS FOR WHAT HAPPENS BEHIND THE SCENES I E THE NON FUNCTIONAL REQUIREMENTS

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Chapter 14. Enterprise Design Patterns

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8MZNWZUIVKM IVL \PM Â¹QTQ\QM[Âº (ERE ARE THREE OF THE MOST IMPORTANT NON FUNCTIONAL REQUIREMENTS YOU RE LIKELY TO FACE

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)OH[LELOLW\ 0DLQWDLQDELOLW\ DQG ([WHQVLELOLW\ &LEXIBILITY 9OU NEED TO CHANGE YOUR SYSTEM WITHOUT GOING THROUGH SOME BIG DEVELOPMENT CYCLE 9OU MIGHT NEED TO SWAP IN THE hLIMITED TIME SPECIAL OFFERv COMPONENTS FOR A BIG SALE 9OU MIGHT lND A BUG IN A NEW COMPONENT AND NEED TO SWAP IN THE OLDER COMPONENT TEMPORARILY 9OU NEED YOUR SYSTEM TO BE mEXIBLE -AINTAINABILITY 9OU MIGHT NEED TO CHANGE DATABASE VENDORS AND UPDATE YOUR SYSTEM QUICKLY 9OU MIGHT GET OBSCURE BUGS AND NEED TO TRACK THEM DOWN !3!0 4HE ADMINS MIGHT DECIDE TO RESTRUCTURE THE COMPANY S NAMING SERVICE AND YOU LL HAVE TO ADJUSTÂ&#x2C6;RIGHT NOW 9OU NEED YOUR SYSTEM TO BE MAINTAINABLE %XTENSIBILITY 4HE GUYS OVER IN MARKETING MIGHT NEED A NEW FEATURE TO LAND THAT BIG CLIENT 9OUR USERS MIGHT DEMAND THAT YOU SUPPORT A BRAND NEW FEATURE THAT THEIR BROWSERS HAVE 9OUR SYSTEM HAD BETTER BE EXTENSIBLE

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Chapter 14. Enterprise Design Patterns

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)TQOVQVO W]Z ^MZVIK]TIZ[ !LL OF THE * %% PATTERNS RELY HEAVILY ON COMMON SOFTWARE DESIGN PRINCIPLES YOU RE PROBABLY VERY FAMILIAR WITH )N THE NEXT FEW PAGES WE mING AROUND SEVERAL TERMS FOR THESE DESIGN PRINCIPLES $IFFERENT PEOPLE AND BOOKS MIGHT HAVE DIFFERENT PERSPECTIVES ON THE SAME TERMS SO WE RE GIVING YOU OUR DElNITIONS NOW SO THAT YOU LL KNOW WHAT WE MEAN

&RGH WR LQWHUIDFHV !S YOU RECALL AN INTERFACE IS A KIND OF A CONTRACT BETWEEN TWO OBJECTS 7HEN A CLASS IMPLEMENTS AN INTERFACE IT S SAYING IN EFFECT h-Y OBJECTS CAN SPEAK YOUR LANGUAGE v !NOTHER HUGE BENElT OF INTERFACES IS POLYMORPHISM -ANY CLASSES CAN IMPLEMENT THE SAME INTERFACE 4HE CALLING OBJECT DOESN T CARE WHO IT S TALKING TO AS LONG AS THE CONTRACT IS UPHELD &OR EXAMPLE THE WEB CONTAINER CAN USE ANY COMPONENT THAT IMPLEMENTS THE 3ERVLET INTERFACE

6HSDUDWLRQ RI &RQFHUQV &RKHVLRQ 7E ALL KNOW THAT WHEN WE SPECIALIZE THE CAPABILITIES OF OUR SOFTWARE COMPONENTS THEY GET EASIER TO CREATE MAINTAIN AND REUSE ! NATURAL FALLOUT OF SEPARATING CONCERNS IS THAT COHESION TENDS TO INCREASE #OHESION MEANS THE DEGREE TO WHICH A CLASS IS DESIGNED FOR ONE COHESIVE TASK OR PURPOSE

+LGH &RPSOH[LW\ (IDING COMPLEXITY OFTEN GOES HAND IN HAND WITH SEPARATING CONCERNS &OR INSTANCE IF YOUR SYSTEM NEEDS TO COMMUNICATE WITH A LOOKUP SERVICE IT S BEST TO HIDE THE COMPLEXITY OF THAT OPERATION IN A SINGLE COMPONENT AND ALLOW ALL THE OTHER COMPONENTS THAT NEED ACCESS TO THE LOOKUP SERVICE TO USE THAT SPECIALIZED COMPONENT 4HIS APPROACH SIMPLIlES ALL OF THE SYSTEM COMPONENTS THAT ARE INVOLVED

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Chapter 14. Enterprise Design Patterns

22 GHVLJQ SULQFLSOHV

5WZM LM[QOV XZQVKQXTM[ /RRVH &RXSOLQJ "Y THEIR VERY NATURE // SYSTEMS INVOLVE OBJECTS TALKING TO EACH OTHER "Y CODING TO INTERFACES YOU CAN REDUCE THE NUMBER OF THINGS THAT ONE CLASS NEEDS TO KNOW ABOUT ANOTHER CLASS TO COMMUNICATE WITH IT 4HE LESS TWO CLASSES KNOW ABOUT EACH OTHER THE MORE LOOSELY COUPLED THEY ARE TO EACH OTHER ! VERY COMMON APPROACH WHEN CLASS ! WANTS TO USE METHODS IN CLASS " IS TO CREATE AN INTERFACE BETWEEN THE TWO /NCE CLASS " IMPLEMENTS THIS INTERFACE CLASS ! CAN USE CLASS " VIA THE INTERFACE 4HIS IS USEFUL BECAUSE LATER ON YOU CAN USE AN UPDATED CLASS " OR EVEN AN ENTIRELY DIFFERENT CLASS AS LONG AS IT UPHOLDS THE CONTRACT OF THE INTERFACE

5HPRWH 3UR[\ 4ODAY WHEN A WEB SITE GROWS THE ANSWER IS TO LASH TOGETHER MORE SERVERS AS OPPOSED TO UPGRADING A SINGLE HUGE MONOLITHIC SERVER 4HE OUTCOME IS THAT *AVA OBJECTS ON DIFFERENT MACHINES IN THEIR OWN SEPARATE HEAPS HAVE TO COMMUNICATE WITH EACH OTHER ,EVERAGING THE POWER OF INTERFACES A REMOTE PROXY IS AN OBJECT LOCAL TO THE hCLIENTv OBJECT THAT PRETENDS TO BE A REMOTE OBJECT 4HE PROXY IS REMOTE IN THAT IT IS REMOTE FROM THE OBJECT IT IS EMULATING 4HE CLIENT OBJECT COMMUNICATES WITH THE PROXY AND THE PROXY HANDLES ALL THE NETWORKING COMPLEXITIES OF COMMUNICATING WITH THE ACTUAL hSERVICEv OBJECT !S FAR AS THE CLIENT OBJECT IS CONCERNED IT S TALKING TO A LOCAL OBJECT

,QFUHDVH 'HFODUDWLYH &RQWURO $ECLARATIVE CONTROL OVER APPLICATIONS IS A POWERFUL FEATURE OF * %% #ONTAINERS -OST COMMONLY THIS DECLARATIVE CONTROL IS IMPLEMENTED USING THE APPLICATION S DEPLOYMENT DESCRIPTOR OR $$ -ODIFYING THE $$ GIVES US THE POWER TO CHANGE SYSTEM BEHAVIORS WITHOUT CHANGING CODE 4HE $$ IS AN 8-, lLE THAT CAN BE MAINTAINED AND UPDATED BY NON PROGRAMMERS 4HE MORE THAT WE WRITE OUR WEB APPLICATIONS TO LEVERAGE THE POWER OF THE $$ THE MORE ABSTRACT AND GENERIC OUR CODE BECOMES

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Chapter 14. Enterprise Design Patterns

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8I\\MZV[ \W []XXWZ\ ZMUW\M UWLMT KWUXWVMV\[ 7E VE TALKED AT A VERY THEORETICAL LEVEL ABOUT HOW * %% PATTERNS CAN HELP SIMPLIFY COMPLEX WEB APPLICATIONS 7E VE ALSO TALKED ABOUT THE SOFTWARE DESIGN PRINCIPLES THAT UNDERLIE * %% PATTERNS 7ITH THAT FOUNDATION IN PLACE LET S GET OUR FEET WET BY TALKING ABOUT A FEW OF THE SIMPLER * %% PATTERNS !LL THREE OF THE PATTERNS WE RE ABOUT TO DISCUSS SHARE THE GOAL OF MAKING REMOTE MODEL COMPONENTS MANAGEABLE

$ )DEOH 7KH %HHU $SS *URZV /NCE UPON A TIME THERE WAS A SMALL DOT COM THAT HAD A WEBSITE THAT OFFERED HOME BREWING RECIPES ADVICE INGREDIENTS AND SUPPLIES FOR BEER AlCIONADOS "EING A SMALL COMPANY WITH BIG PLANS THEY HAD ONLY ONE PRODUCTION SERVER TO SUPPORT THE SITE BUT THEY HAD CREATED TWO SEPARATE SOFTWARE DEVELOPMENT TEAMS TO GROW THE APPLICATION 4HE lRST TEAM KNOWN AS THE h7EB $ESIGNERSv FOCUSED THEIR ATTENTIONS ON THE VIEW COMPONENTS OF THE SYSTEM 4HE SECOND TEAM KNOWN AS THE h"USINESS 4EAMv FOCUSED ON THE CONTROLLER COMPONENTS 2ACHEL S FOCUS AND THE MODEL COMPONENTS +IM S AREA 3HUIRUPDQFH LV UHDOO\ EHFRPLQJ D ELJ LVVXH :HÂ·YH JRW D VPDOO EXGJHW IRU KDUGZDUH QRZ EXW , NQRZ ZHÂ·OO KDYH WR EH UHDG\ WR VSOLW RII PRUH SLHFHV RI WKH DSS ZKHQ WKH WLPH FRPHV

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Chapter 14. Enterprise Design Patterns

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0W_ \PM *][QVM[[ <MIU []XXWZ\[ \PM _MJ LM[QOVMZ[ _PMV \PM 5>+ KWUXWVMV\[ IZM Z]VVQVO WV WVM 2>5 !S LONG AS THE BUSINESS GUYS KEEP THE INTERFACES TO THEIR MODEL COMPONENTS CONSISTENT EVERYONE WILL BE HAPPY 4HE TWO KEY INTERFACE POINTS IN THEIR DESIGN ARE WHEN THE CONTROLLER l RST INTERACTS WITH A MODEL COMPONENT STEPS AND BELOW AND THEN LATER WHEN A *30 VIEW INTERACTS WITH THE BEAN IT NEEDS STEPS AND BELOW

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Chapter 14. Enterprise Design Patterns

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Chapter 14. Enterprise Design Patterns

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4YPICALLY IN * %% APPLICATIONS THERE WILL BE A NUMBER OF COMPONENTS THAT ALL USE THE SAME *.$) SERVICE 7HILE A COMPLEX APPLICATION MIGHT USE SEVERAL DIFFERENT REGISTRIES SUCH AS *.$) AND 5$$) FOR WEB SERVICE ENDPOINTS AN INDIVIDUAL COMPONENT WILL TYPICALLY NEED ACCESS TO ONLY ONE REGISTRY )N GENERAL A SINGLE 3ERVICE ,OCATOR WILL SUPPORT A SINGLE SPECIl C REGISTRY

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Cohesion is increased for all of these Business Delegates.

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7ELL THERE ARE OTHER *AVA RELATED REGISTRIES BESIDES *.$)Â&#x2C6;2-) AND *INI COME TO MIND /F THOSE THREE *.$) IS PROBABLY THE BEST CHOICE FOR MOST WEB APPS IT S EASY AND POWERFUL !LTHOUGH THE AUTHORS WOULD PERSONALLY LOVE TO SEE *INI TAKE ITS RIGHTFUL PLACE IN THE DISTRIBUTED WORLD 9OU MIGHT ALSO BE DEALING WITH NON *AVA REGISTRIES LIKE 5$$) )N ANY CASE THE PATTERNS WILL STILL WORK EVEN THOUGH THE CODE CHANGES OF COURSE

)T SEEMS LIKE THESE PATTERNS ARE FOREVER ADDING A NEW LAYER OF OBJECTS TO THE ARCHITECTURE 7HY IS THIS APPROACH SO COMMON

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,ET S TAKE THE 3ERVICE ,OCATOR AS AN EXAMPLE )N THE EVENT THAT YOUR REGISTRY GETS A NEW NETWORK ADDRESS AND OR REGISTRY INTERFACE IT S FAR EASIER TO MODIFY A SINGLE 3ERVICE ,OCATOR THAN CHANGE A WHOLE FLOTILLA OF "USINESS $ELEGATES )N GENERAL SEPARATION OF CONCERNS BUYS US A LOT OF FLEXIBILITY AND MAINTAINABILITY

)N YOUR EXAMPLES SO FAR YOU VE TAKEN 0/*/S THAT WERE LOCAL AND MADE THEM REMOTE )SN T IT MORE LIKELY THAT ) LL BE FACED WITH INTEGRATING EXISTING %*"S INTO MY WEB APP

"Y 0/*/S WE ASSUME YOU MEAN h0LAIN /LD *AVA /BJECTSv OF COURSE !ND YES IT IS LIKELY THAT YOU LL BE INTEGRATING %*"S INTO YOUR APP !ND IN FACT THAT S YET ANOTHER REASON TO USE THESE TWO PATTERNS YOUR CONTROLLER AND VIEW SHOULD NEVER HAVE TO CARE WHETHER THE MODEL IS A LOCAL *AVA"EAN A REMOTE 0/*/ OR AN ENTERPRISE *AVA"EAN %*" 7ITHOUT USING 3ERVICE,OCATOR AND "USINESS $ELEGATE THAT DIFFERENCE MEANS A LOTÂ&#x2C6; ENTERPRISE BEANS AND PLAIN OLD REMOTE OBJECTS DON T USE THE SAME LOOKUP CODE 5SING THESE PATTERNS YOU CAN ENCAPSULATE THE ISSUES RELATED TO HOW AND WHERE THE MODEL IS DISCOVERED AND USED AND KEEP THE CONTROLLER HAPPY AND CLUELESS SO THAT YOU WON T HAVE TO CHANGE YOUR CONTROLLER CODE WHEN THE BUSINESS GUYS CHANGE THINGS AND MOVE THINGS AROUND ON THE BUSINESS TIER 9OU LL UPDATE ONLY THE 3ERVICE ,OCATOR AND POSSIBLY THE "USINESS $ELEGATE

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Chapter 14. Enterprise Design Patterns

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Chapter 14. Enterprise Design Patterns

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<PMZMÂ¼[ OWWL VM_[ IVL JIL VM_[ 4HE PREVIOUS ARCHITECTURE SUCCEEDS IN HIDING COMPLEXITY FROM BOTH THE CONTROLLERS AND THE *30S !ND IT MAKES GOOD USE OF THE "USINESS $ELEGATE AND 3ERVICE ,OCATOR PATTERNS

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Chapter 14. Enterprise Design Patterns

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calls validate(). Struts provides ActionErrors to manage validation errors.

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Chapter 14. Enterprise Design Patterns

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Chapter 14. Enterprise Design Patterns

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e the -This pattern (among others), helps separat tasks performed by application developers from the tasks performed by web designers.

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