Spring AOP Examples

Create a maven project and add following dependencies.

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.sks</groupId>
  <artifactId>aoptutorial</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  
  <dependencies>
  	<dependency>
  		<groupId>org.springframework</groupId>
  		<artifactId>spring-context</artifactId>
  		<version>4.2.0.RELEASE</version>
  	</dependency>
  	
  	<dependency>
  		<groupId>org.aspectj</groupId>
  		<artifactId>aspectjrt</artifactId>
  		<version>1.7.4</version>
  	</dependency>
  	
  	<dependency>
  		<groupId>org.aspectj</groupId>
  		<artifactId>aspectjtools</artifactId>
  		<version>1.7.4</version>
  	</dependency>
  
  
  </dependencies>
</project>

Before Advice example

Let’s create one class called Employee.

package com.sks;

public class Employee {
	
	private String name;
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

EmployeeBeforeAspect.java

package com.sks.aspect;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

@Aspect
public class EmployeeBeforeAspect {
	
	//In the below execution expression * means any return type
	@Before("execution(* com.sks.Employee.getName())")
	public void getNameBeforeAdvice() {
		System.out.println("Executing \"Advice\" before getName method of Employee class.");
	}
}

applicationContext.xml file

<?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:p="http://www.springframework.org/schema/p"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xsi:schemaLocation="http://www.springframework.org/schema/beans 
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">

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

	<bean id="emp" class="com.sks.Employee">
		<property name="name" value="Arjun"></property>
	</bean>

	<bean id="empBeforeAspect" class="com.sks.aspect.EmployeeBeforeAspect" />
</beans>

Main method class for testing

package com.sks;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class EmployeeTesting {

	public static void main(String[] args) {

		ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

		Employee e = (Employee) context.getBean("emp");
		e.setName("Arjun");
		System.out.println("Name : " + e.getName());
		
		context.close();
	}
}

Output:

In the below example, you can see that before getName() method is invoked on Employee object ‘e’, getNameBeforeAdvice() has been executed.

More AOP expressions

@Before("execution(* com.sks.Employee.get*())")

Defining point cut and join point

We can define point cut expressions like below.

package com.sks.aspect;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;

@Aspect
public class EmployeeBeforeAspect {

	@Before("getNamePointCut()")
	public void getNamePointcutAdvice() {
		System.out.println("Executing pointcut advice for getEmployee method.");
	}
	
	@Before("getNamePointCut())")
	public void getNameJointPointAdvice(JoinPoint joinPoint) {

		System.out.println("Executing join point advice at location : " + joinPoint.toString());
	}

	@Pointcut("execution(* com.sks.service.EmployeeService.getEmployee())")
	public void getNamePointCut() {

	}
	
}	

After Advice example

package com.sks.aspect;

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

@Aspect
public class EmployeeAfterAspect {
	
	@After("args(name,surname)")
	public void getNameAfterAdvice(String name, String surname) {
		
		System.out.println("After advice being executed.");
		System.out.println("Passed argument are : " + name + " " + surname);
	}
	
}

After Throwing Advice example

In this example, we will throw one exception forcefully so that the advice is executed

package com.sks;

public class Employee {
	
	private String name;
	private String surName;

	public void setName(String name) throws Exception {
		this.name = name;
		if(name.equals("Amar")) {
			
			throw new Exception();
			
		}
	}
	
	public void setFullName(String name, String surName) {
		this.name = name;
		this.surName = surName;
	}
	
	//getter and setter methods
	
	@Override
	public String toString() {
		return "Employee [name=" + name + ", surName=" + surName + "]";
	}

}

package com.sks.aspect;

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

@Aspect
public class EmployeeAfterAspect {
		
	@AfterThrowing("within(com.sks..*)")
	public void logException(JoinPoint joinPoint) {
		System.out.println("Exception is thrown in class at : " + joinPoint.toString());
		
	}
}

Around Advice example

package com.sks.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;

@Aspect
public class EmployeeAroundAspect {
		
	@Around("execution(* *.getName())")
	public Object getNameAroudAdvice(ProceedingJoinPoint proceedingJoinPoint) {
		
		Object result = null;
		System.out.println("Before executing around advice for getName method.");
		
		try {
			result = proceedingJoinPoint.proceed();
		} catch (Throwable e) {
			e.printStackTrace();
		}
		
		System.out.println("After executing around advice for getName method.");
		
		return result;
	}
}