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How to implement After Throwing Advice using Classic Spring Proxy-Based AOP in Java ?.

A simple application to demonstrate how to implement After Throwing Advice using Classic Spring Proxy-Based AOP in Java.

Step 1:- Divide.java Interface

package com.hubberspot.classic.aop.afterthrowsadvice;

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

public interface Divide {

 public int divide(int a , int b);

}




Step 2:- DivideImpl.java Service Implementation Class

package com.hubberspot.classic.aop.afterthrowsadvice;

// It is the implementation class for the 
// Division service. It just calculates and returns 
// division of two numbers passed to it as arguments.
// If denominator passed to it as zero than 
// new ArithmeticException() is thrown.

public class DivideImpl implements Divide {

 @Override
 public int divide(int a, int b) {

  if(b != 0) {

   return a/b;

  }

  else {

   throw new ArithmeticException();

  }

 }

}




Step 3:- After Throwing Advice Implementation class

package com.hubberspot.classic.aop.afterthrowsadvice;

import java.lang.reflect.Method;
import org.springframework.aop.ThrowsAdvice;

// This class is a simple After Throwing Advice which implements 
// interface called as ThrowsAdvice. This interface is the 
// marker interface that provides Spring additional info 
// for handling a thrown exception. We have defined a method 
// by name afterThrowing.

public class AfterThrowsDivisionAdvice implements ThrowsAdvice {

 // All the parameters to this method are optional except 
 // Exception exception that indicates which exception is to be
 // handled by this advice.

 public void afterThrowing(Method method, Object[] args, Object target, 
   Exception exception) {

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

 }

}




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">


<!-- After Throwing Advice:- Advice is been configured as beans -->
<bean id="afterThrowsDivision"
class="com.hubberspot.classic.aop.afterthrowsadvice.AfterThrowsDivisionAdvice" />

<!-- Implementation Class -->
<bean id="divideImpl" class="com.hubberspot.classic.aop.afterthrowsadvice.DivideImpl" />

<!-- Proxy Implementation Class:- This configuration binds advices to the 
implementation code using a proxy factory bean. In order to apply the advice 
final bean has to be proxied. Spring's ProxyFactoryBean is a factory that 
creates a proxy which implies one or more interceptors to bean -->

<bean id="divide" class="org.springframework.aop.framework.ProxyFactoryBean">
  
<!-- This proxy bean definition has three properties 
  
1. target :- It tells ProxyFactoryBean to which bean it will be 
making proxy. 
  
2. intercepterNames :- Interceptor Names property is configured 
as a list of interceptor or advices which is being applied to 
this proxy. 
  
3. proxyInterfaces :- It just tells to ProxyFactoryBean that 
which interface Proxy bean has to implement. 
  
-->
  
  
 <property name="target">
  <ref bean="divideImpl" />
 </property>

 <property name="interceptorNames">
  <list>
   <value>afterThrowsDivision</value>
  </list>
 </property>

 <property name="proxyInterfaces">
  <value>com.hubberspot.classic.aop.afterthrowsadvice.Divide</value>
        </property>
</bean>
</beans>



Step 5:- Test class

package com.hubberspot.classic.aop.afterthrowsadvice;

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

public class DivisionTest {

 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 after_throwing_advice.xml placed
  // at classpath of our application.


  ApplicationContext context = 
    new ClassPathXmlApplicationContext("after_throwing_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 Divide object. Without implementing new keyword we 
  // have injected object of Divide just by reading an xml 
  // configuration file.

  Divide divide = (Divide)context.getBean("divide");

  int result = divide.divide(10 , 5);

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

  result = divide.divide(10, 0);

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


 }

}




Output of the program : 


 
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