Spring学习笔记之bean生命周期

时间：2020-10-13 10:06:30|栏目：JAVA代码|点击：次

前言

上一篇文章主要学习了下bean的配置、注入、自定义属性编辑器，今天来熟悉bean的生命周期。

任何一个事物都有自己的生命周期，生命的开始、生命中、生命结束。大家最熟悉的应该是servlet 的生命周期吧。和 servlet 一样 spring bean 也有自己的生命周期。

在开发中生命周期是一个很常见的名词，基本每种编程语言都能找到与它关联的。关于bean的生命周期我在网上也找了好多，基本都差不多。这里我主要是想通过代码来验证，毕竟学的知识都是一样的，都是学的Java，最重要的是动手练习，这样印象更深。

下面是它生命周期的描述，我们通过demo来进行验证。

下图是它执行的顺序。

一、创建LiftCycle类实现BeanFactoryAware,BeanNameAware,InitializingBean,DisposableBean,ApplicationContextAware5个接口方法

package Cuiyw.Spring.Service;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
public class LifeCycle implements BeanFactoryAware,BeanNameAware,InitializingBean,DisposableBean,ApplicationContextAware{
 
 private String name;
 public String getName() {
 System.out.println("getName name="+name);
 return name;
 }
 public void setName(String name) {
  System.out.println("setName name="+name);
 this.name = name;
 }
 public void afterPropertiesSet() throws Exception {
 // TODO Auto-generated method stub
  System.out.println("InitializingBean.afterPropertiesSet()");
 }
 public void setBeanName(String arg0) {
 // TODO Auto-generated method stub
 System.out.println("BeanNameAware.setBeanName");
 }
 public void setBeanFactory(BeanFactory arg0) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("BeanFactoryAware.setBeanFactory");
 }
 public void destroy() throws Exception {
 // TODO Auto-generated method stub
 System.out.println("DisposableBean.destroy");
 }
 public void myInit() {
 System.out.println("【init-method】调用<bean>的init-method属性指定的初始化方法");
 }
 public void myDestory() {
 System.out.println("【destroy-method】调用<bean>的destroy-method属性指定的初始化方法");
 }
 public void setApplicationContext(ApplicationContext arg0) throws BeansException {
 // TODO Auto-generated method stub
  System.out.println("ApplicationContextAware.setApplicationContext");
 } 
}

二、注册InstantiationAwareBeanPostProcessor接口

package Cuiyw.Spring.Service;

import java.beans.PropertyDescriptor;

import org.springframework.beans.BeansException;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor;

public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor{
 public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("InstantiationAwareBeanPostProcessor.postProcessAfterInitialization");
 return bean;
 }
 public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("InstantiationAwareBeanPostProcessor.postProcessBeforeInitialization");
 return bean;
 }
 public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("InstantiationAwareBeanPostProcessor.postProcessAfterInstantiation");
 return true;
 }
 public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("InstantiationAwareBeanPostProcessor.postProcessBeforeInstantiation");
 return null;
 }
 public PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean,
  String beanName) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("InstantiationAwareBeanPostProcessor.postProcessPropertyValues");
 return pvs;
 }
}

三、注册BeanPostProcessor接口

其实InstantiationAwareBeanPostProcessor继承BeanPostProcessor，所以在上面我也实现了BeanPostProcessor接口的方法

package Cuiyw.Spring.Service;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
public class MyBeanPostProcessor implements BeanPostProcessor {
 public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("BeanPostProcessor.postProcessAfterInitialization ");
 return bean;
 }
 public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("BeanPostProcessor.postProcessBeforeInitialization");
 return bean;
 }
}

四、注册BeanFactoryPostProcessor接口

package Cuiyw.Spring.Service;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
 public void postProcessBeanFactory(ConfigurableListableBeanFactory arg0) throws BeansException {
 // TODO Auto-generated method stub
 System.out.println("BeanFactoryPostProcessor.postProcessBeanFactory");
 }
}

五、在上下文中配置

这里还是在上一个博客demo的基础上进行修改，为了有其他干扰，我先把service去掉了。

<?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 id="beanPostProcessor" class="Cuiyw.Spring.Service.MyBeanPostProcessor"></bean>
<bean id="instantiationAwareBeanPostProcessor" class="Cuiyw.Spring.Service.MyInstantiationAwareBeanPostProcessor"></bean>
<bean id="beanFactoryPostProcessor" class="Cuiyw.Spring.Service.MyBeanFactoryPostProcessor"></bean>
<bean id="lifeCycle" class="Cuiyw.Spring.Service.LifeCycle" init-method="myInit" destroy-method="myDestory">
<property name="name" value="cuiyw1"></property>
</bean>
</beans>

六、在main中使用bean

package Cuiyw.SpringAop;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import Cuiyw.Spring.IService.IService;
import Cuiyw.Spring.Service.LifeCycle;

public class App 
{
 public static void main( String[] args )
 {
 ApplicationContext context=new ClassPathXmlApplicationContext(new String[]{"ApplicationContext.xml"});
 BeanFactory factory=context;
 LifeCycle lifeCycle=factory.getBean("lifeCycle",LifeCycle.class);
 lifeCycle.setName("cuiyw2");
  System.out.println("lifeCycle.name="+lifeCycle.getName());
 ((ClassPathXmlApplicationContext)factory).registerShutdownHook(); 
 /*service=(IService)factory.getBean("ServiceA");
 service.service("Cuiyw ServiceA"); 
 service=(IService)factory.getBean("ServiceImpl");
 service.service("Cuiyw ServiceImpl"); */
 }
}

七、输入打印结果

可以发现输出的顺序和上面图的顺序基本一致。

总结

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