Sunday, 18 November 2018

Spring AOP AspectJ @Before Annotation Example [Apply to multiple methods] | Spring Tutorial

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Mastering @Before with Multiple Methods

Hello developers! Today we are diving deep into Spring Aspect-Oriented Programming (AOP). Specifically, we'll learn how to apply the @Before annotation to multiple methods at once. This is a massive time-saver for any Java programmer!

Why Apply Advice to Multiple Methods?

In a real-world application, you might have hundreds of methods. If you want to log a message or check security before every single one of them, adding code to each method individually is a nightmare. AOP allows you to define this logic in one place and apply it everywhere with a single rule.

The Power of Pointcut Expressions

The secret to targeting multiple methods lies in the Pointcut Expression. Instead of naming one specific method, we can use wildcards. For example:

execution(* add*()): This targets any method that starts with the word "add".
execution(* com.service.*.*(..)): This targets every single method inside the service package!

Setting Up Your Project

In the video, we walk through setting up an EmployeeService. We then create a LoggingAspect class where we use the @Before annotation. By carefully writing our expression, we can make our logging code run before addEmployee(), modifyEmployee(), and deleteEmployee() all at once!

Key Benefits of This Approach

By mastering multiple method targeting, you keep your Business Logic 100% clean. Your service classes don't need to know anything about logging or security—they just focus on their main job. This makes your code easier to maintain, test, and scale.

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Spring AOP AspectJ @Before Annotation Example [Apply to multiple methods] | 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>

        <!-- Spring AOP + AspectJ -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-aop</artifactId>

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

        </dependency>

        <dependency>

            <groupId>org.aspectj</groupId>

            <artifactId>aspectjrt</artifactId>

            <version>1.9.1</version>

        </dependency>

        <dependency>

            <groupId>org.aspectj</groupId>

            <artifactId>aspectjweaver</artifactId>

            <version>1.9.1</version>

        </dependency>

    </dependencies>

</project>

EmployeeService.java

package com.ram.service;

public class EmployeeService

{

    public void addEmployee()

    {

        System.out.println("addEmployee() method is called \n");

    }

    public void addEmployee(String name, int age)

    {

        System.out.println(

                "addEmployee(String name, int age) method is called \n");

    }

    public void modifyEmployee()

    {

        System.out.println("modifyEmployee() method is called \n ");

    }

    public void deleteEmployee()

    {

        System.out.println("deleteEmployee() method is called \n ");

    }

}

LoggingAspect.java

package com.ram.Aspect;

import org.aspectj.lang.JoinPoint;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Before;

@Aspect

public class LoggingAspect

{

    @Before("execution(* com.ram.service.EmployeeService.*Employee(..))")

    public void logBefore(JoinPoint joinPoint)

    {

        System.out.print("logBefore() is running!");

        System.out.println(", before "

                + joinPoint.getSignature().getName() + " method");

    }

}

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"

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

    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

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

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

    <aop:aspectj-autoproxy />

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

    <!-- Aspect -->

    <bean id="logAspect" class="com.ram.Aspect.LoggingAspect" />

</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("employeeService", EmployeeService.class);

        employeeService.addEmployee();

        employeeService.addEmployee("Peter", 45);

        employeeService.modifyEmployee();

        employeeService.deleteEmployee();

    }

}

Output

Nov 03, 2018 10:47:42 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@4bf558aa: startup date [Sat Nov 03 10:47:42 IST 2018]; root of context hierarchy

Nov 03, 2018 10:47:42 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

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

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

logBefore() is running!, before addEmployee method

addEmployee() method is called

logBefore() is running!, before addEmployee method

addEmployee(String name, int age) method is called

logBefore() is running!, before modifyEmployee method

modifyEmployee() method is called

logBefore() is running!, before deleteEmployee method

deleteEmployee() method is called