Spring @PostConstruct and @PreDestroy example

In Spring, you can either implements InitializingBean and DisposableBean interface or specify the init-method and destroy-method in bean configuration file for the initialization and destruction callback function. In this article, we show you how to use annotation @PostConstruct and @PreDestroy to do the same thing.

Note
The @PostConstruct and @PreDestroy annotation are not belong to Spring, it’s located in the J2ee library – common-annotations.jar.

@PostConstruct and @PreDestroy

A CustomerService bean with @PostConstruct and @PreDestroy annotation

package com.mkyong.customer.services;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

public class CustomerService
{
	String message;
	
	public String getMessage() {
	  return message;
	}

	public void setMessage(String message) {
	  this.message = message;
	}
	
	@PostConstruct
	public void initIt() throws Exception {
	  System.out.println("Init method after properties are set : " + message);
	}
	
	@PreDestroy
	public void cleanUp() throws Exception {
	  System.out.println("Spring Container is destroy! Customer clean up");
	}
	
}

By default, Spring will not aware of the @PostConstruct and @PreDestroy annotation. To enable it, you have to either register ‘CommonAnnotationBeanPostProcessor‘ or specify the ‘<context:annotation-config />‘ in bean configuration file,

1. CommonAnnotationBeanPostProcessor

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
	http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

	<bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" />

	<bean id="customerService" class="com.mkyong.customer.services.CustomerService">
		<property name="message" value="i'm property message" />
	</bean>
		
</beans>

2. <context:annotation-config />

<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-2.5.xsd
	http://www.springframework.org/schema/context
	http://www.springframework.org/schema/context/spring-context-2.5.xsd">

	<context:annotation-config />

	<bean id="customerService" class="com.mkyong.customer.services.CustomerService">
		<property name="message" value="i'm property message" />
	</bean>
		
</beans>

Run it

package com.mkyong.common;

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

import com.mkyong.customer.services.CustomerService;

public class App 
{
    public static void main( String[] args )
    {
    	ConfigurableApplicationContext context = 
    	  new ClassPathXmlApplicationContext(new String[] {"Spring-Customer.xml"});
	
    	CustomerService cust = (CustomerService)context.getBean("customerService");
    	
    	System.out.println(cust);
    	
    	context.close();
    }
}

Output

Init method after properties are set : im property message
com.mkyong.customer.services.CustomerService@47393f
...
INFO: Destroying singletons in org.springframework.beans.factory.
support.DefaultListableBeanFactory@77158a: 
defining beans [customerService]; root of factory hierarchy
Spring Container is destroy! Customer clean up

The initIt() method (@PostConstruct) is called, after the message property is set, and the cleanUp() method (@PreDestroy) is call after the context.close();