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Spring @PostConstruct and @PreDestroy example

2015-08-21 19:36 501 查看
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()
;
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