A Brief Introduction to AspectOriented Programming Zhenxiao Yang

A Brief Introduction to Aspect-Oriented Programming Zhenxiao Yang

Historical View Of Languages n n n Procedural language Functional language Object-Oriented language

Procedural Language n n Also named imperative language Describe n n An explicit sequence of steps to follow to produce a result Examples: Basic, Pascal, C

Functional Language Also named declarative language Describe n n n relationships between variables in terms of functions or inference rules. Examples n n n Prolog: Logical programming language Haskell: Functional language

Object-Oriented Programming n Describe n n n A set of objects And communications among them to produce a result Basic features n n n Encapsulation Inheritance Polymorphism

OOP (cont’d) n Example languages n n n First OOP language: SIMULA-67 (1970) Smalltalk, C++, Java Many other: n n Ada, Object Pascal, Objective C, DRAGOON, BETA, Emerald, POOL, Eiffel, Self, Oblog, ESP, POLKA, Loops, Perl, VB Are OOP languages procedural?

We Need More n The nice things about OOP n n Modular structure The problems of OOP n n Issues distributed in different modules result in tangled code. Example: logging

We Need More (cont’d) n We need a solution to this tangled-code problem n One of the sound answer is Aspect. Oriented Programming

Basic Concepts in AOP n n n cross-cut aspect joint pointcut advice introduction

Aspect. J by Example

Aspect. J by Example (cont’d) n n n Define pointcuts Define advice Introduction

Pointcuts n pointcut n n n pointcut move(): call(void Figure. Element. set. XY(int, int)) || call(void Point. set. X(int)) || call(void Point. set. Y(int)) || call(void Line. set. P 1(Point)) || call(void Line. set. P 2(Point)); pointcut produce call(void Figure. make*(. . )) pointcut set. XY(Figure. Element fe, int x, int y): call(void fe. set. XY(x, y));

Advices n Advice n n after(): move(){ System. out. println(“A figure element moved. ”); } after (Figure. Element fe, int x, int y): set. XY(fe, x, y){ System. out. println(fe + “ moved to ” +x, + “ , ” + y); }

Aspects aspect Figure. Log{ pointcut set. XY(Figure. Element fe, int x, int y): calls(void fe. set. XY(x, y)); after(Figure. Element fe, int x, int y): set. XY(fe, x, y){ System. out. println(fe + " moved to (" + x + ", " + y + "). "); } }

Introduction n n Add members to a set of Classes Change inheritance structure of classes

Introduction (cont’d) aspect Point. Observing { private Vector Point. observers = new Vector(); public static void add. Observer(Point p, Screen s) { p. observers. add(s); } public static void remove. Observer(Point p, Screen s) { p. observers. remove(s); }. . }

Introduction (cont’d) public class A 1{ function foo(){…} } public class A 2{ function foo(){…; super. foo(); …} } public class A 3{ function foo(){…; super. foo(); …} } aspect A 1 A 2 A 3{ declare parents: A 2 extends A 1; declare parents: A 3 extends A 2; }

Introduction (cont’d) public class A 1{ function foo(){…} } public class A 2{ function foo(){…; super. foo(); …} } public class A 3{ function foo(){…; super. foo(); …} } aspect A 1 A 3 A 2{ declare parents: A 3 extends A 1; declare parents: A 2 extends A 3; }

What Can Aspect. J Do for Us n Developing n n Production n n Tracing, Logging, and Profiling Pre- and Post-Conditions Contract Enforcement Change Monitoring Synchronization Context Passing Providing Consistent Behavior Introduction

Conclusion and Open Issues n AOP vs OOP n n n AOP also has runtime overhead n n n AOP is not substitute of OOP AOP makes OOP more powerful We should use OOP as much as possible Reuse of aspects Tool support

Related Work n n Aspect. J Reflection and meta-object protocols n n Meta-object provides mechanism to control over base-objects Subject-Oriented Programming n

Thank You!