Monday, 12 November 2018

Spring AOP After Advice Example | Spring Tutorial

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Mastering Spring AOP: After Advice Explained

Aspect-Oriented Programming (AOP) is a powerful way to handle cross-cutting concerns like logging, security, or transaction management. In this guide, we dive deep into one of the most useful types of advice: After Advice.

What is After Advice?

In Spring AOP, After Advice is logic that executes immediately after a "join point" (usually a method execution) finishes. Think of it as a "finally" block in Java—it runs regardless of whether the method completed successfully or threw an exception.

Why Use After Advice?

It’s perfect for cleanup tasks! Whether you need to close a database connection, release a resource, or log that a method attempt has finished, After Advice keeps your business logic clean by separating these repetitive tasks into a single Aspect.

Practical Example

Using the @After annotation, you can target specific methods or entire packages. This tutorial shows you exactly how to set up your pointcuts so your advice triggers exactly when you need it to, making your application more modular and easier to maintain.

Key Takeaway: After Advice ensures your "teardown" logic always runs, providing a safety net for your application's state management.

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Spring AOP After Advice Example | Spring Tutorial

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ram.core</groupId>

    <artifactId>SpringDemo</artifactId>

    <packaging>jar</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>SpringDemo</name>

    <url>http://maven.apache.org</url>

    <properties>

        <spring.version>5.0.5.RELEASE</spring.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <!-- Spring 5 dependencies -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>${spring.version}</version>

        </dependency>

    </dependencies>

</project>

EmployeeService.java

package com.ram.service;

public class EmployeeService

{

    public String getEmployeeName(int age)

    {

        System.out.println("Get Employee Information");

        if(age == 28)

        {

            return "Peter";

        }

        return "Dave";

    }

}

LoggingAdvice.java

package com.ram.Advice;

import java.lang.reflect.Method;

import org.springframework.aop.AfterReturningAdvice;

public class LoggingAdvice implements AfterReturningAdvice

{

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

            Object target) throws Throwable

    {

        System.out.println("Logging advice is applied after the method "

                + method.getName() + " in the target Object "

                + target.getClass().getName());

        for (Object object : args)

        {

            System.out.println(object);

        }

        System.out.println("returnValue = " + returnValue);

    }

}

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 

    xmlns:context="http://www.springframework.org/schema/context"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

    http://www.springframework.org/schema/beans/spring-beans-4.3.xsd

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

    http://www.springframework.org/schema/context/spring-context-4.3.xsd">

    <bean id="employeeService" class="com.ram.service.EmployeeService"></bean>

    <bean id="loggingAdvice" class="com.ram.Advice.LoggingAdvice"></bean>

    <bean id="employeeServiceProxy" class="org.springframework.aop.framework.ProxyFactoryBean">

        <property name="target" ref="employeeService"></property>

        <property name="interceptorNames">

            <list>

                <value>loggingAdvice</value>

            </list>

        </property>

    </bean>

</beans>

App.java

package com.ram.core;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ram.service.EmployeeService;

public class App

{

    public static void main(String[] args)

    {

        ApplicationContext context = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

        System.out.println("---------------------------------------");

        EmployeeService employeeService = context.getBean("employeeServiceProxy",

                EmployeeService.class);

        employeeService.getEmployeeName(28);

    }

}

Output

Oct 12, 2018 8:06:21 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@6ebc05a6: startup date [Fri Oct 12 08:06:21 IST 2018]; root of context hierarchy

Oct 12, 2018 8:06:22 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [applicationContext.xml]

---------------------------------------

Get Employee Information

Logging advice is applied after the method getEmployeeName in the target Object com.ram.service.EmployeeService

28

returnValue = Peter