Aspect-Oriented Programming M. Sc. Juan Carlos Olivares Rojas Department of Computer and System Instituto Tecnol贸gico de Morelia jcolivar@itmorelia.edu.mx http://antares.itmorelia.edu.mx/~jcolivar/
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Agenda • Introduction • Aspect-Oriented Programming Fundamentals • Examples • Project of Unit 4
Objectives of the Session
• The students will know a new programming paradigm: AOP (Aspect-Oriented Programming). • The students will development a program usin this paradigm or refactoring existing applications.
Software Development Today
Software Evolution Evoluci贸n del SW
Software Evolution Evoluci贸n del SW
Software Development Problems
• A complex system can visualize like as combined implementation of multiple concerns
Software Development Problems class Book { ….. <all things about book> <error handling> … } class Partner { ….. <all things about Partner> <error handling> <access controlling> }
class Rent {….. <all things about Rent> <error handling> <access controlling> }
Software Development Problems class BookStore { private Book [] books ; private Partner [] partners; public BookStore() { â&#x20AC;Ś public void load( Partner p, Book b) { if validControlAccess() then{ // code of the method } else{ throwException(); } }
Access Control
public void addPartner(Partner p){ if validContolAccess() then{ // code of the method } else{ throwException(); } } // the rest of the class methods }
Tyranny of the Dominant Decomposition
â&#x20AC;˘ â&#x20AC;˘
Descomposition by Form, Color or size We must choose only one principal model
Tyranny of the Dominant Decomposition •
Order by Form
•
Order by Color
Color-Form Hierarchy â&#x20AC;˘
We must elect one principal model. In this case: color and later, form
AOP Definition • AOP was created by Gregor Kickzales and his Research Team at Palo Alto Research Center in 1996. • “ An Aspect is a modular unit that is spreand in another functional units. The aspects exist in the design stage as in the implementación stage…” • An Aspect is a concept that it’s difficult encapsulate clear and easily.
AOP â&#x20AC;˘ An aspect is the unit which encapsulate a cross-cutting concern. â&#x20AC;˘ AOP promoves the separation of concerns through mechanisms which abstract and compose this concepts troughout the system.
Traditional Structure of a Compiler PROGRAMA
Lenguaje
Compilador o IntĂŠrprete
EJECUTABLE
Compiling Process in POA PROGRAMA DE COMPONENTES
Lenguaje base
PROGRAMA DE ASPECTOS 1
Lenguaje de aspectos 1
... ...
TEJEDOR (WEAVER)
EJECUTABLE
PROGRAMA DE ASPECTOS N
Lenguaje de aspectos N
AOP Program Structure
Program
AOP Program Structure
POA Concepts JoinPoint
It’s a well-defined position inside of object-oriented code, for instance, the declaración of a method.
Pointcut
It’s a set of conditions applied to a JoinPoint, when the conditions are true, it will active and execute an Execution Point asigned at this PointCut.
Advice
It’s a Fragment of Code tha it’s executed when is actived PointCut.
Aspect
It’s the combination of JoinPoint, Pointcuts and Advices.
An Aspect Definition
Aspect Control { JoinPoint securityOperations = call s BookStore.loan & calls BookStore.addPartner& ... Before securityOperations: { if !=(validControlAcces()) then{ throwsExcepcion(); } }
AOP and OOP Relation OOP: common concerns AOP: crosscuting concerns
Class A
Class A1 Attb1
Clase A2 Attb 3
Attb2 Method 1 Method 1
Method 2
OOP Evolution to AOP
POA Advantages â&#x20AC;˘ A code less complicated, more natural and more reduced. â&#x20AC;˘ More facilities to think about the concerns, since they are separate and dependencies between them are minimal. â&#x20AC;˘ An easier code to debug and to mantein.
AOP Tools • Langauges for Programming Aspects: • AspectJ: A Java Extension. The most popular. • AspectC++, AspectS, CAESAR. • .NET Languages: Weave.NET, Source Weave.
Class Bank Problem public class Bank { // other declarations public double processDebit(long idAccount, double amount) { // openning a transaction try { // retrieve account // business validation // business logic associated with debit // persistencia del nuevo estado // traceo del movimiento para auditoria // cierre exitoso de la transacci贸n (commit) return new amount account; } catch (Exception e) { // trace the audit exception // close abnormal transaction (rollback) // relauch the exception in superior layers } } // other business process declarations }
Transaction Persistence Traceability
Aspectual Descomposition • Separation of concerns • Aims to isolate cross cutting concerns • Each one of these concerns will be implemented in a separate unit.
Aspectual Recomposition
AOP Bank Version cio n sa c nc ia
Tr an d
// another business methods declarations }
ilid a
}
Pe rsi s te
// validaciones del negocio // debit business logic return new amount account;
Tr az ab
public double processDebit(long account, double amount) {
ali d
ad
public class Bank { // other declarations
Hello World with Aspects package mx.edu.itmorelia.aspects; public class HW { private String message; public HW() { this.message = â&#x20AC;&#x153;Hello World"; } public void setMessge(String M){ this.menssage = M; } public String getMessage(){ return this.message; } public void showMessage(){ System.out.println(this.message); } }
Hello World with Aspects package mx.edu.itmorelia.aspects; public class HelloWorld { public static void main(String[] args) { HW H; H= new HW(); H.showMenssage(); } }
Hello World with Aspects package mx.edu.itmorelia.aspects; public aspect Aspect { pointcut messagesToPrint() : call (void HW.showMessage()); before(): messagesToPrint(){ System.out.println(“Hi everybody!"); } after(): messagesToPrint(){ System.out.println(“Chao everybody!"); } }
Alternatives to Aspects • Languages (OO, Componet-Based) • Design Patterns • Reflection
PointCut
PointCut • When a particular methos is executed: – execution(void
Point.setX(int))
• When a method is invocated: call(void Point.setX(int)) • When a error handling is invocated: handler(ArrayOutOfBoundsException) • When the object is actually executed: this(SomeType).
PointCut Examples • When a method belongs to a class: – within(MyClass)
• When the JoinPoint is in the control flow of a call main method we need to use: cflow • The target point refers to any possible JoinPoint
36
Pointcut Designator Wildcards • It’s possible to use wildcards • What do the next instructions do? – – – – – –
execution(* *(..)) call(* set(..)) execution(int *()) call(* setY(long)) call(* Point.setY(int)) call(*.new(int, int)) 37
PointCut call join points
a Line dispatch
execution join points
• JoinPoint Types
– Methods – Constructors – Get/Set – Exception Handler
PointCut Examples • We can applicate the next operations: or (“||”), and (“&&”) and not (“!”).
• Examples: – – – –
target(Point) && call(int *()) call(* *(..)) && (within(Line) || within(Point)) within(*) && execution(*.new(int)) !this(Point) && call(int *(..))
Advice Type • • • • • •
before advice after advice after returning after throwing after around advice
40
Parameterized Advice • We can acces to the context of a JoinPoint as follow: • pointcut
setXY(FigureElement fe, int x, int y): call(void FigureElement.setXY(int, int)) && target(fe) && args(x, y);
• after(FigureElement fe, int x, int y) returning: setXY(fe, x, y) { System.out.println(fe + " moved to (" + x + ", " + y + ")."); } 41
Another Example Display
* FigureElement
Figure makePoint(..) makeLine(..)
Point getX() getY() setX(int) setY(int) moveBy(int, int)
moveBy(int, int)
2
Line getP1() getP2() setP1(Point) setP2(Point) moveBy(int, int)
HistoryUpdating
Another Example HTTPRequest getCookies() getRequestURI()(doc) getSession() getRequestedSessionId() ...
SessionInterceptor requestMap(request) beforeBody(req, resp) ...
Session getAttribute(name) setAttribute(name, val) invalidate() ...
HTTPResponse getRequest() setContentType(contentType) getOutptutStream() setSessionId(id) ... 43
Servlet
Project for Unit 4 • Developping a J2ME project which implements the Triangle and Ecuation2 class. • The validation and error handling process must be programming in aspects. • The development team will have two members exlcusively.
Project for Unit 4 • The project consist in two parts: programming (70%) and modelling (20%) (Aspect extension for UML) • The program must be test on a mobile devices (not emulators) • Deadline: Thursday, December 4 at class.
References • Mejía, P. (2008), Programación Orientada a Aspectos, CINVESTAV, México. • Quintero, A. (2000), Visión General de la Programación Orientada a Aspectos. Languages and Information System Department. Informatic and Estadistic Faculty, Sevilla University, Spain. • Rodriguez M., POA, Gerente Académicas, Microsoft Cono Sur
Relaciones
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