Spring @PostConstruct and @PreDestroy example

from: http://www.mkyong.com/spring/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.

NoteThe @PostConstruct and @PreDestroy annotation are not belong to Spring, 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 messagecom.mkyong.customer.services.CustomerService@47393f...INFO: Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@77158a: defining beans [customerService]; root of factory hierarchySpring 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();