BeanPostProcessor :- It is an interface that defines callback methods by which you can provide your own instantiation logic and your own custom logic before and after the bean creation. along with this you can perform some additional logic or your own task before and after initializing the bean.

BeanPostProcessor Example

Bean_Post_Process.java

package com.manish;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

public class Bean_Post_Process implements BeanPostProcessor {

    @Override
    public Object postProcessAfterInitialization(Object bean, String name)
            throws BeansException {
        // TODO Auto-generated method stub
        System.out.println("After Intializing the Bean:="+name);
        return bean;
    }

    @Override
    public Object postProcessBeforeInitialization(Object bean, String name)
            throws BeansException {
        // TODO Auto-generated method stub
        System.out.println("Before Intializing the Bean:="+name);
        return bean;
    }




}

Student.java

package com.manish;

public class Student 
{
    private int id;
    private String name;


    Student()
    {
        System.out.println("Student Bean");
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    public void init()
    {
        System.out.println("Initializing Bean Student");
    }

    public void destroy()
    {
        System.out.println("Destroy Bean Student");
    }



}

app-context.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:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">

   <context:annotation-config/>

 <bean id="student" class="com.manish.Student" init-method="init" destroy-method="destroy">
    <property name="id" value="1216"></property>
    <property name="name" value="manish"></property>

</bean> 




</beans>

App.java

package com.app;

    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.AbstractApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    import com.manish.Course;
    import com.manish.Student;

    public class App {

        /**
         * @param args
         */
        public static void main(String[] args) {
            // TODO Auto-generated method stub

            AbstractApplicationContext ctx=new ClassPathXmlApplicationContext(new String[]{"app-context.xml"});


            Student stu=(Student)ctx.getBean("student");


            System.out.println("Rollno:="+stu.getId());
            System.out.println("Name:="+stu.getName());
            ctx.registerShutdownHook();



        }

    }

Output:-

      Student Bean
Initializing Bean Student
Rollno:=1216
Name:=manish
Destroy Bean Student

The above example show that how the BeanPostProcessor interface can be used and to override it's callback methods postProcessAfterInitialization and postProcessBeforeInitialization.

These callbacks methods can be called after creating and before deletion of an bean