Using annotation for configuring advices

We again take example of before advice.

Now we add @Aspect at the bean level. But on the method of the Aspect class, we can have annotations depending on what type of method or better advice they are. For before type advice we have @Before annotation.

Creating the aspect class

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

@Aspect
public class LoggingAspect {

    //TODO: Try other pointcut expressions also as mentioned in slide no. 203-207
    @Before("execution(public * apply*(..))")
    public void log(JoinPoint joinPoint) {
        System.out.println("common logging code executed for : "+joinPoint);
    }    
}

Now the bean class is quite cleaner, as we are annotation:

<?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/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

    <aop:aspectj-autoproxy />
    
    <bean id="customerService" class="service.CustomerServiceImpl" />
    
    <bean id="loggingAspect" class="ex2.LoggingAspect" />

</beans>

Here we are simply logging a simple text before entering the methods. Consider the case when we want to print about arguments.

This is where JoinPoint object comes into picture.

More about JoinPoint Object

Changing the before advice to take care of arguments , etc of the methods.

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

@Aspect
public class LoggingAspect2 {

    @Before("execution(public * apply*(..))")
    public void log(JoinPoint joinPoint) {
        Object proxyObject = joinPoint.getThis();
        Object targetBean = joinPoint.getTarget();
        Object[] args = joinPoint.getArgs();
        Signature signature = joinPoint.getSignature();
        //some logging code here
    }
}

In the above xml file just change the class name of LoggingAspect to LoggingAspect2.

As the names of the method suggest :

• this : The current executing object that has been intercepted


• target : The target of the execution (typically our object)


• args -  method args


• signature - method signation of the joinpoint

One of the reason why aspectJ was adopted by the spring was because of v.powerful and easy to learn pointcut expression, which define where our aspects will execute.