Introduction to Aspect Oriented Programming

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Introduction toAspect Oriented Programming

• Presented By
• Kotaiah Choudary. Ravipati
• M.Tech IInd Year.
• School of Info. Tech.

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Contents

• Introduction
• AOP Methodology
• AOP Languages
• AspectJ

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Programming Methodologies
Introduction
4
Present Design Problem
Introduction

• The architects dilemma
• How much design is too much?

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Terminology
Introduction

• 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

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Terminology cont
Introduction

• 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

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Typical Application
Introduction
Accounting
ATM
Database
Logging
Persistence
System
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Implementation by Traditional Languages
Introduction
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Implementation by AOP
Introduction
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AOP Methodology
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?

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AOP Development Stages
AOP Methodology
Integrating all concerns
Identify concerns
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AOP Languages
AOP Languages

• AOP Language Specification
• Describes the language constructs and syntax
• Specification for implementing the individual
  concerns and rules for weaving different concerns

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AOP Languages cont
AOP Languages

• 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.

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AspectJ
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

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AspectJ cont
AspectJ

• 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

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Example
AspectJ

• Public class Logging//class
• public void check( )
• System.out.println("Inside Logging Class
  Method")
• public class ATM //class
• public 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( ) //Advice
• System.out.println( I am from Log aspect")
• Logging logg new Logging()
• logg.check()

Name of Pointcut
before after around
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Example cont
AspectJ

• 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

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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.asp2
• http//en.wikipedia.org/wiki/Aspect_oriented_progr
  amming
• Erik Putrycz, Guy Bernard, IEEE 2002, Using
  Aspect Oriented Programming to build a portable
  load balancing service