关于spring bean的生命周期,是深入学习spring的基础,也是难点,本篇文章将采用代码+图文结论的方式来阐述spring bean的生命周期,
本篇文章将阐述清楚下图。
1.程序目录结构
2.applicationContext.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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> <bean class="com.demo.dao.UserDao" id="userDao" scope="singleton" init-method="myInit" destroy-method="myDestroy"> <property name="userName" value="Alan_beijing"/> </bean> <bean class="com.demo.dao.MyBeanPostProcessor" id="myBeanPostProcessor"/> </beans>
3.UserDao.java
package com.demo.dao; import org.springframework.beans.BeansException; import org.springframework.beans.factory.*; import org.springframework.beans.factory.config.BeanPostProcessor; import org.springframework.context.ApplicationContext; import org.springframework.context.ApplicationContextAware; import org.apache.log4j.Logger; public class UserDao implements BeanNameAware, BeanFactoryAware, ApplicationContextAware, InitializingBean, DisposableBean{ private String userName; private int count = 0; public String getUserName() { return userName; } //2.属性注入,注入属性为userName public void setUserName(String userName) { count++; System.out.println(count + ":注入属性userName="+userName); this.userName = userName; } //1.无参构造函数,实例化时调用该构造函数 public UserDao() { count++; System.out.println(count + ":调用构造函数UserDao()"); } //3.实现BeanNameAware,获取bean id public void setBeanName(String s) { count++; System.out.println(count + ":调用setBeanName()获取bean id,bean id=" + s); } //4.实现BeanFactoryAware,获取bean工厂 public void setBeanFactory(BeanFactory beanFactory) throws BeansException { count++; System.out.println(count + ":调用setBeanFactory()获取bean工厂,beanFactory=" + beanFactory); } //5.实现ApplicationContextAware,获取bean上下文 public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { count++; System.out.println(count + ":调用setApplicationContext()获取bean上下文,applicationContext=" + applicationContext); } //6.实现InitializingBean,获取afterPropertiesSet public void afterPropertiesSet() throws Exception { count++; System.out.println(count + ":调用afterPropertiesSet()"); } //7.自定义初始化方法myInit() public void myInit() { count++; System.out.println(count + ":调用自定义myInit()"); } //8.实现DisposableBean,获取destroy() public void destroy() throws Exception { count++; System.out.println(count + ":destroy()"); } //9.自定义销毁方法myDestroy() public void myDestroy() { count++; System.out.println(count + ":调用自定义destroy()"); } }
4.MyBeanPostProcessor.java
package com.demo.dao; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanPostProcessor; public class MyBeanPostProcessor implements BeanPostProcessor { public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { System.out.println("=====调用postProcessBeforeInitialization()====="); return bean; } public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { System.out.println("=====调用postProcessAfterInitialization()====="); return bean; } }
1.test.java
package com.demo.test; import com.demo.dao.UserDao; import org.junit.Test; import org.springframework.context.support.AbstractApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MyTest { @Test public void test() { //定义容器并初始化 //ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); AbstractApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); applicationContext.getBean(UserDao.class); //只有关闭容器时,才会调用destroy方法 applicationContext.registerShutdownHook(); } }
2.测试结果
三 分析
通过如上测试结果,bean生命周期流程大致如下:
1.装配bean
bean装配为bean生命周期第一环节。所谓装配bean,指将java对象转换为bean的过程。在该示例中,UserDao.jave和MyBeanPostProcessor通过xml方式转化为bean。
注意:spring框架支持四种方式装配bean:xml方式,java代码方式,自动装配和混合装配方式
2.加载applicationContext.xml并实例化
加载并实例化bean为bean生命周期的第二环节。本文示例通过ClassPathXmlApplicationContext()来加载并,当bean为singleton时,该过程就实例化对象,而不需要等待
调用applicationContext.getBean()获取bean时才实例化对象,这与prototype是不一样的。
3.属性注入
bean属性注入为bean生命周期第三环节,采用反射方式注入bean.
4.实现BeanNameAware,获取bean id
该过程为bean生命周期的第四环节,实现该接口,可以获取bean的id
5.实现BeanFactoryAware,获取bean 工厂
该过程为bean生命周期第五环节,通过实现BeanFactoryAware获取bean工厂
6.实现ApplicationContextAware,获取运用上下文
该过程为bean生命周期第六环节,通过实现ApplicationContextAware接口,获取bean上下文
7.调用Bean后置处理器,before
该过程为bean生命周期第七环节,通过实现后置处理器BeanPostProcessor获取before和after,该过程是通过AOP方式实现的,在before和after之间,发生如下8,9过程。
8.实现InitializingBean的afterPropertiesSet(),获取初始化方法
该过程为bean生命周期第八环节,通过实现InitializingBean,获取afterPropertiesSet()
9.调用自定义初始化方法,init-method
该过程为bean生命周期第九环节,实现自定义初始化方法
10.调用Bean后置处理器after
该过程为bean生命周期第十环节,后置处理器最后环节
11.关闭容器AbstractApplicationContext.registerShutDownHook()
该环节为bean生命周期第十一环节,关闭容器
12.调用DisposableBean的destroy()
该过程为bean生命周期第十二环节,实现DisposableBean接口,调用destroy()
13.调用定制化销毁方法destroy-method
该过程为bean生命周期最后环节,调用自定义销毁方法destroy-method
三 版权区