Spring @PostConstruct和@PreDestroy實例

在Spring中,既可以實現 InitializingBean和DisposableBean接口或在bean配置文件中指定 init-method 和 destroy-method 在初始化和銷燬回調函數。在這篇文章中,我們將介紹如何使用 @PostConstruct 和 @PreDestroy 註解來做同樣的事情。

注:@PostConstruct和@PreDestroy 標註不屬於 Spring,它是在J2EE庫- common-annotations.jar。

@PostConstruct 和 @PreDestroy

一個 CustomerService Bean使用 @PostConstruct 和 @PreDestroy 註釋

package com.yiibai.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");
}

}

默認情況下,Spring不會意識到@PostConstruct和@PreDestroy註解。要啓用它,要麼註冊「CommonAnnotationBeanPostProcessor」,要麼在bean配置文件的<context:annotation-config />‘ 指定,

1. CommonAnnotationBeanPostProcessor

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

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

2. <context:annotation-config />

<context:annotation-config />

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

執行結果

package com.yiibai.common;

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

import com.yiibai.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();
}

}

輸出結果

Init method after properties are set : im property message
[email protected]
...
INFO: Destroying singletons in org.springframework.beans.factory.
[email protected]:
defining beans [customerService]; root of factory hierarchy
Spring Container is destroy! Customer clean up

initIt()方法(@PostConstruct)被調用時,消息屬性設置後 cleanUp() 方法(@PreDestroy)是在context.close()執行後被調用;

下載源代碼 –  http://pan.baidu.com/s/1qX2W6xI