AOP is…let us see!

Objectives

• How to implement AOP using Spring?
• What is AOP?

Environment

• Eclipse (Indigo or any)

Library

• Spring framework 3.x (jars) some of them! 3.x http://www.springsource.org/spring-framework
• Other jars you can find them on http://mvnrepository.com/ or http://www.jarfinder.com

•      aopalliance-1.0.jar
•      aspectjtools-1.6.0.jar
•      cglib-nodep-2.2.3.jar
•      commons-logging-1.1.1.jar

The Story:

Every time a user login we would like to keep a record of his login action.

( 1 ) Create Java Project  & Add jars to lib Folder

• Create a new java project “SpringAOP”
• Create folder “lib”
• Copy jar files to “lib”
• Add jars to the java building path

( 2 ) Java Code (User.java + Logger.java + Main.java)

User.java plain java bean

package com.hmkcode.beans;

public class User {

	//constructor
	public User(){}

	//method login
	public void login(){
		System.out.println("User is trying to login");
	}
}

Logger.java logs user login activity

package com.hmkcode.beans;

import java.util.Calendar;

public class Logger {

    public void log(){
      System.out.println("user has logged in @"+Calendar.getInstance().getTime());
    }
}

Main.java runs the application

package com.hmkcode;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.hmkcode.beans.User;

public class Main {

  public static void main(String args[]){

  // Laod spring-config.xml file
     ApplicationContext ctx = new ClassPathXmlApplicationContext("com/hmkcode/config/spring-config.xml");
      ((User) ctx.getBean("user")).login();
   }
}

( 3 ) XML Configuration File (spring-config.xml)

<?xml version="1.0" encoding="UTF-8"?>
	<beans 	xmlns="http://www.springframework.org/schema/beans"
		xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		xmlns:aop="http://www.springframework.org/schema/aop"
		xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-3.0.xsd


http://www.springframework.org/schema/aop


http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">

		<aop:aspectj-autoproxy />
		<bean id="user" class="com.hmkcode.beans.User" />
		<bean id="logger" class="com.hmkcode.beans.Logger" />

		<aop:config>
			<aop:aspect id="aspectUserLogger" ref="logger" >
     			<!-- @After -->
     			<aop:pointcut id="pointCutAfter"
				expression="execution(* com.hmkcode.beans.User.login(..))" />
     			<aop:after method="log" pointcut-ref="pointCutAfter" />
  			</aop:aspect>
		</aop:config>
</beans>

Place java files and xml file as shown bleow

( 4 ) Test the Application

You should get something similar to the result below (of course, not the same date and time)

( 5 ) What is AOP?

Simply, (after/before) a method “A” is called call another method “B” ! without writing “code” calling B.

AOP = Aspect Oriented Programming

Download Source Code: SpringAOP.zip