Spring AOP - Custom Annotation


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As per pointcut expressions in may be the case that they get applied to some other beans for which advice is not intended. For example, consider the following expression:

execution(* com.tutorialspoint.*.getAge(..)) 

A new spring bean added with getAge() method and the advice will start getting applied to it although it may not be intended. To achieve it, we can create a custom annotation and annotate the methods on which the advice is to be applied.

@Before("@annotation(com.tutorialspoint.Loggable)")

To understand above mentioned concepts related to @Before Advice, let us write an example which will implement @Before Advice. To write our example with few advices, let us have working Eclipse IDE in place and follow the following steps to create a Spring application:

StepDescription
1Update the project Student created under chapter Spring AOP - Application.
2Update the bean configuration and run the application as explained below.

Here is the content of Logging.java file. This is actually a sample of aspect module which defines methods to be called at various points.

package com.tutorialspoint;

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

@Aspect
public class Logging {

   /** 
    * This is the method which I would like to execute
    * before a selected method execution.
    */
   @Before("@annotation(com.tutorialspoint.Loggable)")
   public void beforeAdvice(){
      System.out.println("Going to setup student profile.");
   }  
}

Following is the content of the Loggable.java file:

package com.tutorialspoint;

public @interface Loggable {

}

Following is the content of the Student.java file:

package com.tutorialspoint;

public class Student {
   private Integer age;
   private String name;

   public void setAge(Integer age) {
      this.age = age;
   }
   public Integer getAge() {
	  System.out.println("Age : " + age );
      return age;
   }
   
   public void setName(String name) {
      this.name = name;
   }
   @Loggable
   public String getName() {
      System.out.println("Name : " + name );
      return name;
   }
   
   public void printThrowException(){
	   System.out.println("Exception raised");
       throw new IllegalArgumentException();
   }
}

Following is the content of the MainApp.java file:

package com.tutorialspoint;

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

public class MainApp {
   public static void main(String[] args) {
      ApplicationContext context = 
             new ClassPathXmlApplicationContext("Beans.xml");

      Student student = (Student) context.getBean("student");

      student.getName();
      student.getAge();     
   }
}

Following is the configuration file Beans.xml:

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

   <aop:aspectj-autoproxy/>

   <!-- Definition for student bean -->
   <bean id="student" class="com.tutorialspoint.Student">
      <property name="name"  value="Zara" />
      <property name="age"  value="11"/>      
   </bean>

   <!-- Definition for logging aspect -->
   <bean id="logging" class="com.tutorialspoint.Logging"/> 
      
</beans>

Run Project

Once you are done with creating source and configuration files, run your application. Right click on MainApp.java in your application and use run as Java Application command. If everything is fine with your application, this will print the following message:

Going to setup student profile.
Name : Zara
Age : 11


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