Introduction to Aspect Oriented Programming Presented By: Kotaiah Choudary. Ravipati M.Tech IInd...

Introduction to

Aspect Oriented Programming

Presented By:Kotaiah Choudary. Ravipati

M.Tech IInd Year.

School of Info. Tech.

19 August 2005 Aspect Oriented Programming 2

Contents

• Introduction

• AOP Methodology

• AOP Languages

• AspectJ

19 August 2005 Aspect Oriented Programming 3

Programming Methodologies

m/c Programming

Assembly Programming

Procedural Programming

OO Programming

AO Programming

Programming Methodologies Evaluation

Concern Abstraction

Function Abstractio

n

Object Abstraction

Introduction

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Present Design Problem

• The architect’s dilemma– How much design is too much?

Introduction

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Terminology

• Concern– A specific requirement or consideration that must be

addressed in order to satisfy the overall system goal– E.g. Banking system:

Customer and Account management, Interbanking transactions, ATM transactions,

Persistence of all entities, Transaction integrity, Authorization of access to various services, Logging, Security, Error checking, Policy enforcement

Introduction

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Terminology cont

• Core concerns– Central functionality of a Business logic (single

module)– Customer and Account management, Interbanking

transactions, ATM transactions

• Crosscut concerns– System-level, peripheral requirements (multiple

modules)– Persistence of all entities, Transaction integrity,

Authorization of access to various services, logging, Security, Error checking, Policy enforcement

Introduction

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Typical Application

Accounting

ATM

Database

System

Introduction

Persistence Logging

Business Logic

Concern

Persistence

LoggingImplementation

modules

Accounting

ATM

Database

System

Persistence

Logging

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Implementation by Traditional Languages

Accounting Module

ATM Module

Database Module

Logging Module

API invocations

Introduction

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Implementation by AOP

Accounting Module

ATM Module

Database Module

Logging ModuleLogging Aspect

APIInvocation

Automatically Weaving Invocations

Aspect: A modular unit of crosscutting concern implementation

Introduction

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AOP Methodology

• The idea behind AOP is “Separation of concern”

• AOP builds upon Existing Methodologies (OOP, Procedural programming), augmenting them with concepts and constructs in order to modularize crosscutting concerns.

• Now, concern consists of what?

AOP Methodology

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AOP Development StagesAOP Methodology

Business Logic

Security

Logging

Persistence

Identify concerns

Integrating all concerns

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AOP Languages

• AOP Language Specification– Describes the language constructs and

syntax– Specification for implementing the

individual concerns and rules for weaving different concerns

AOP Languages

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AOP Languages cont

• AOP language implementation– Verifies the code and translates the code into

an executable form– Implementation done by two steps

• Combining individual concerns using the weaving rules - Weaving

• Then converting result into executable code.

• Some AOP Languages– AspectJ, Aspect#, AspectC++, PHPaspect.

AOP Languages

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AspectJ

• Aspect-oriented extension to Java language• Language Specification• Language Implementation

– Concern by Java Language– Weaving rules by extension Tools

• Crosscutting in AspectJ– Implementation of the weaving rules by the compiler – 2 Types:

• Dynamic Crosscutting– Weaving of new Behavior into execution of program

• Static Crosscutting– weaving of modifications into the static structure, to support the

Dynamic Crosscutting

AspectJ

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AspectJ cont

• Crosscutting Elements– Join Point

• Well-defined points in the execution of a program

– Pointcut• A means of referring to collections of join points and certain values at

those join points

– Advice• Method-like constructs to define additional behavior at join points

– Introduction• Instruction that changes to the classes, interfaces of the system

– Compile time Declaration• Instruction for adding compile time warnings and errors to the system

– Aspect• Unit of modular crosscutting implementation

AspectJ

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ExamplePublic class Logging{//classpublic void check( ) {

System.out.println("Inside Logging Class Method"); }}

public class ATM { //classpublic void foo(int number, String name) {

System.out.println("Inside foo Method"); }public static void main(String[] args) {

MyClass myObject = new MyClass( ); myObject.foo(1, “SIT"); } }

public aspect Log { //Aspect pointcut callPointcut( ) : call(void ATM.foo(int, String)); //Pointcut

before( ) : callPointcut( ) { //AdviceSystem.out.println( “I am from Log aspect"); Logging logg= new Logging();logg.check(); } }

AspectJ

Name of Pointcut

beforeafteraround

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Example cont

• Compile– ajc ATM.java Log. java – output:

• ATM.class Log.class

• Run– java ATM– Output:

• I am from Log aspect Inside foo Method

Here let us assume Logging class already compiled

AspectJ

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References

• AspectJ Cookbook , O'Reilly, December 2004• Aspectj In Action - Practical Aspect-Oriented Programming,

2003• http://www.codeproject.com/gen/design/aop.asp#2• http://en.wikipedia.org/wiki/Aspect_oriented_programming• Erik Putrycz, Guy Bernard, IEEE 2002, Using Aspect

Oriented Programming to build a portable load balancing service