How to implement After Advice using @AspectJ Annotation-Driven AOP in Java ?.

A simple application to demonstrate how to implement After Advice using @AspectJ Annotation-Driven AOP in Java.

Step 1:- Create a Interface Sum.java

package com.hubberspot.aspectj.annotation.afteradvice;

// Its a simple interface for the Sum service.
// It contains one single method called as addition().
// This method takes in two arguments both of the type
// int.
public interface Sum {

 public int addition(int a , int b);

}

Step 2:- SumImpl.java Service Implementation Class

package com.hubberspot.aspectj.annotation.afteradvice;

// It is the implementation class for the 
// Sum service. It just calculates and returns 
// sum of two numbers passed to it as arguments.

public class SumImpl implements Sum {

 @Override
 public int addition(int a, int b) {
  System.out.println("Addition method called ...");
  return (a + b);

 }

}


Step 3:- After Advice Implementation class

package com.hubberspot.aspectj.annotation.afteradvice;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;

//@Aspect annotation treats this Java class as 
//Aspect. Its not ordinary POJO class.

@Aspect
public class AfterSumAdvice {

 // Method after() is a after advice
 // implemented by providing @After annotation.
 // This annotation takes in Pointcut expression, which 
 // indicates when this advice executes.
 // This Pointcut expression tells that after() advice
 // will execute addition method of Sum interface.
 // The after advice takes in JoinPoint which here represents
 // method execution.

 @After("execution(* com.hubberspot.aspectj.annotation.afteradvice.Sum.addition(..))")
 public void after(JoinPoint joinPoint) {

  System.out.println("Call after addition method ...");

 }

}


Step 4 :- Spring Configuration file


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<?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-3.1.xsd
   http://www.springframework.org/schema/aop
   http://www.springframework.org/schema/aop/spring-aop-3.1.xsd">

   <aop:aspectj-autoproxy></aop:aspectj-autoproxy>

     <!-- Implementation Class -->
     <bean id="sum" class="com.hubberspot.aspectj.annotation.afteradvice.SumImpl" />

     <bean id="afterAdvice"
 class="com.hubberspot.aspectj.annotation.afteradvice.AfterSumAdvice" />

</beans>



Step 5:- Test class

package com.hubberspot.aspectj.annotation.afteradvice;

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

public class SumTest {

 public static void main(String[] args) {

  // ApplicationContext is a Spring interface which 
  // provides with the configuration for an application. 
  // It provides us with all the methods that BeanFactory 
  // provides. It loads the file resources in a older 
  // and generic manner. It helps us to publish events to the
  // listener registered to it. It also provides quick support
  // for internationalization. It provides us with the object 
  // requested, it reads the configuration file and provides
  // us with the necessary object required.
  // We are using concrete implementation of AbstractApplicationContext
  // here called as ClassPathXmlApplicationContext because this 
  // bean factory reads the xml file placed in the classpath of 
  // our application. We provide ClassPathXmlApplicationContext
  // with a configuration file called as before_advice.xml placed
  // at classpath of our application. 

  ApplicationContext context = 
    new ClassPathXmlApplicationContext("after_advice.xml");

  // In order to get a object instantiated for a particular bean 
  // we call getBean() method of ClassPathXmlApplicationContext
  // passing it the id for which the object is to be needed. 
  // Here getBean() returns an Object. We need to cast it back 
  // to the Sum object. Without implementing new keyword we 
  // have injected object of Sum just by reading an xml 
  // configuration file.

  Sum sum = (Sum)context.getBean("sum");

  int result = sum.addition(5, 10);

  System.out.println("Result = " + result);


 }

}

Output of the program :