Short description of Spring AOP.

AOP stand for Aspect Oriented Programming 

Aspect - It is concept which a developer wants to implements globally i.e. Think of this as the general feature you want to apply globally to your application (logging etc).
Advice - Code that is used to implement Aspect. A chunk of code that is invoked during program execution, and is a piece of the logic for implementing your aspect.
Joinpoint - A single location in the code where an advice should be executed (such as field access, method invocation , constructor invocation, etc.).
Pointcut - A pointcut is a set of many joinpoints where an advice should be executed.
Targets/Target Objects - The objects you want to apply an aspect or set of aspects to
Introduction - This is the ability to add methods to an object.

Lets take a simple example


==Interface
package springExample;

public interface Adder {

    public int add(int a,int b);

}

==Implementation class

package springExample;

public class AdderImpl implements Adder {

    public int add(int a, int b){
        return a+b;
    }

}
==Execution class

package springExample;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.*;

public class AdderTest {

    public static void main(String args[]){

        Resource resource = new FileSystemResource("src/SpringHelloWorld.xml");    
        BeanFactory factory = new XmlBeanFactory(resource);
       // XmlBeanFactory beanFactory = new XmlBeanFactory(new ClassPathResource("SpringHelloWorld.xml"));
        Adder adder = (Adder)factory.getBean("adder");
        int result = adder.add(10,11);
        System.out.println("Result = " + result);

        result = adder.add(0,0);
        System.out.println("Result = " + result);
    }
}

==AfterAdvice

package springExample;

import java.lang.reflect.Method;

import org.springframework.aop.AfterReturningAdvice;

public class LogAfterReturningAdvice implements AfterReturningAdvice{

    public void afterReturning(Object returnValue, Method method, Object[] args,

    Object target) throws Throwable {

        System.out.println("After Normal Return from Method");

    }

}

==ThrowAdvice

package springExample;

import java.lang.reflect.Method;

import org.springframework.aop.ThrowsAdvice;

public class LogAfterThrowsAdvice implements ThrowsAdvice{

    public void afterThrowing(Method method, Object[] args, Object target,

    Exception exception){

        System.out.println("Exception is thrown on method " + method.getName());

    }

}

==Around Advice

package springExample;

import java.lang.reflect.Method;

import net.sf.cglib.proxy.MethodInterceptor;

import net.sf.cglib.proxy.MethodProxy;

import org.aopalliance.intercept.MethodInvocation;

public class LogAroundAdvice implements MethodInterceptor{

    public Object invoke(MethodInvocation methodInvocation) throws Throwable {

        Object arguments[] = methodInvocation.getArguments();

        int number1 = ((Integer)arguments[0]).intValue();

        int number2 = ((Integer)arguments[1]).intValue();

        if (number1 == 0 && number2 == 0){

            throw new Exception("Dont know how to add 0 and 0!!!");

        }

        return methodInvocation.proceed();

    }

@Override

public Object intercept(Object arg0, Method arg1, Object[] arg2,

MethodProxy arg3) throws Throwable {

// TODO Auto-generated method stub

return null;

}

}

==Before Advice

package springExample;

import java.lang.reflect.Method;

import org.springframework.aop.MethodBeforeAdvice;

public class LogBeforeCallAdvice implements MethodBeforeAdvice

{

    public void before(Method method, Object[] args, Object target) {

        System.out.println("Before Calling the Method>>>>>>>>>>>..");

        System.out.println("method>>>>>>>>>>>>>>"+method.getName());

        for(int i=0;i

        {

        System.out.println("args>>>>>>>>>>>>>>"+args[i].toString());

        }

        System.out.println("target>>>>>>>>>>>>>>" + target.getClass().getName());

    }

}

===XML

===========Out Put

Before Calling the Method>>>>>>>>>>>..

method>>>>>>>>>>>>>>add

args>>>>>>>>>>>>>>10

args>>>>>>>>>>>>>>11

target>>>>>>>>>>>>>>springExample.AdderImpl

After Normal Return from Method

Result = 21

Before Calling the Method>>>>>>>>>>>..

method>>>>>>>>>>>>>>add

args>>>>>>>>>>>>>>0

args>>>>>>>>>>>>>>0

target>>>>>>>>>>>>>>springExample.AdderImpl

After Normal Return from Method

Result = 0