Spring AOP - XML Based Before Advice

Before is an advice type which ensures that an advice runs before the method execution. Following is the syntax of before advice.

Syntax

<aop:config>
   <aop:aspect id = "log" ref = "logging">
      <aop:PointCut id = "PointCut-id" expression = "execution( expression )"/>    
      <aop:before PointCut-ref = "PointCut-id" method = "methodName"/>
   </aop:aspect>
</aop:config>

Where,

• PointCut-id − id of the PointCut.

• methodName − Method name of the function to be called before a called function.

To understand the 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 a working Eclipse IDE in place and use the following steps to create a Spring application.

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

package com.howcodex;

public class Logging {

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

Following is the content of the Student.java file.

package com.howcodex;

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;
   }
   
   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.howcodex;

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:config>
      <aop:aspect id = "log" ref = "logging">
         <aop:PointCut id = "selectAll" 
            expression = "execution(* com.howcodex.Student.getName(..))"/>
         <aop:before PointCut-ref = "selectAll" method = "beforeAdvice"/>
      </aop:aspect>
   </aop:config>

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

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

Run Project

Once you are done 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, it will print the following message.

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