Transcript Aspect Oriented Programming

Introduction to
Aspect Oriented Programming
Presented By:
Kotaiah Choudary. Ravipati
M.Tech IInd Year.
School of Info. Tech.
Contents
•
•
•
•
Introduction
AOP Methodology
AOP Languages
AspectJ
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Introduction
Programming Methodologies
Concern
Abstraction
AO Programming
Function
Abstractio
n
OO Programming
Object
Abstraction
Procedural Programming
Assembly Programming
m/c Programming
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Programming Methodologies
Evaluation
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Introduction
Present Design Problem
• The architect’s dilemma
– How much design is too much?
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Introduction
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
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Introduction
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
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Introduction
Typical Application
Business Logic
Concern
Accounting
ATM
Logging
Persistence
Database
Logging
Persistence
Implementation
modules
System
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Introduction
Implementation by Traditional
Languages
API
invocations
Accounting Module
ATM Module
Logging Module
Database Module
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Introduction
Implementation by AOP
Automatically Weaving
Invocations
Accounting Module
API
Invocation
ATM Module
Logging Aspect
Logging Module
Database Module
Aspect: A modular unit of crosscutting concern
implementation
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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 Methodology
AOP Development Stages
Security
Business
Logic
Identify
concerns
Integrating all
concerns
Logging
Persistence
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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
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.
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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
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
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AspectJ
Example
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"); } }
Name of
Pointcut
public aspect Log { //Aspect
pointcut callPointcut( ) : call(void ATM.foo(int, String)); //Pointcut
before( ) : callPointcut( ) { //Advice
System.out.println( “I am from Log aspect");
before
Logging logg= new Logging();
after
logg.check(); } }
around
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AspectJ
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
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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
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