Spring(九)：Bean的生命周期

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　　Spring Bean的生命周期由多个特定的生命队段组成，可以从两个层面来定义Bean的生命周期。第一层是Bean的作用范围；第二层是实例化Bean所经历的一系列阶段。

BeanFactory中Bean 的生命周期

BeanFactory对Bean的初始化并不是在启动IoC容器时，是在被第一次调用的时候。BeanFactory对于单例(默认singleton)的Bean会进行缓存，第二次用时直接取。
Spring在DefaultSingletonBeanRegistry类中提供了一个用于缓存单例Bean的缓存器，是一个用HashMap实现的缓存器，单例的Bean以beanName为键保存这在这个HashMap中。
BeanFactory-bean-lifeCycle

ApplicationContext中Bean 的生命周期

ApplicationContext则在初始化应用上下文时就实例化所有单例的Bean。如果设置了lazy-init=”true”后，则执行的是懒加载策略，IoC容器启动就不会马上实例化，而是在被调用时实例化。

  1. Bean在应用上下文中的生命周期与在BeanFactory中的生命周期相似，不同的是，如果Bean实现了org.springframework.context.ApplicationContextAware接口，则会增加一个调用该接口方法setApplicationContext()的步骤。
  2. 如果在配置文件(bean.xml)声明了工厂后处理器接口BeanFactoryPostProcessor的实现类，则应用在上下文装载配置文件之后，初始化Bean实例之前将调用postProcessBeanFactory()方法对配置信息进行后处理。工厂后处理器是容器级的，只在应用上下文初始化时调用一次，其目的是完成一些配置文件的加工处理工作。
  3. 另一个不同是ApplicationContext会利用反射机制自动识别出配置文件中定义的BeanPostProcessor，InstantiationAwareBeanPostProcessor，BeanFactoryPostProcessor，并自动将它们注册到应用上下文中；而BeanFactory需要在代码中手工调用addBeanPostProcessor()方法进行注册。
    这些是在应用开发中普遍使用ApplicationContext，而很少使用BeanFactory的原因之一。
  4. 在ApplicationContext中，只需要配置文件中定义工厂后处理器和Bean后处理器，它们就会按预期的方式运行。
    ApplicationConetxt-bean-lifeCycle

示例代码

BeanFactory

  1. Bean
    实现BeanFactoryAware, BeanNameAware, InitializingBean, DisposableBean接口

     package com.smart.beanfactory;
 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;

 //管理Bean生命周期的4个接口
 public class Car implements BeanFactoryAware, BeanNameAware, InitializingBean, DisposableBean {
     private String brand;
     private String color;
     private int maxSpeed;
     private String name;
     private BeanFactory beanFactory;
     private String beanName;

     public Car() {
         System.out.println("调用Car()构造函数。");
     }

     public String getBrand() {
         return brand;
     }

     public void setBrand(String brand) {
         System.out.println("调用setBrand()设置属性。");
         this.brand = brand;
     }

     public String getColor() {
         return color;
     }
     public void setColor(String color) {
         this.color = color;
     }

     public int getMaxSpeed() {
         return maxSpeed;
     }

     public void setMaxSpeed(int maxSpeed) {
         this.maxSpeed = maxSpeed;
     }

     public void introduce(){
         System.out.println("introduce:"+this.toString());
     }

     public String toString() {
         return "brand:" + brand + "/color:" + color + "/maxSpeed:"+ maxSpeed;
     }

     // BeanFactoryAware接口方法
     public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
         System.out.println("调用BeanFactoryAware.setBeanFactory()。");
         this.beanFactory = beanFactory;
     }

     // BeanNameAware接口方法
     public void setBeanName(String beanName) {
         System.out.println("调用BeanNameAware.setBeanName()。");
         this.beanName = beanName;
     }

     // InitializingBean接口方法
     public void afterPropertiesSet() throws Exception {
         System.out.println("调用InitializingBean.afterPropertiesSet()。");
     }

     // DisposableBean接口方法
     public void destroy() throws Exception {
         System.out.println("调用DisposableBean.destory()。");
     }

     //通过<bean>的init-method属性指定初始化方法
     public void myInit() {        
         System.out.println("调用myInit()，将maxSpeed设置为240。");
         this.maxSpeed = 240;
     }
     //通过<bean>的destroy-method属性指定销毁的方法
     public void myDestory() {
         System.out.println("调用myDestroy()。");
     }

     public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
         System.out.println("调用setApplicationContext方法");
     }
 }

  2. MyBeanPostProcessor

     package com.smart.beanfactory;

 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.config.BeanPostProcessor;

 import com.smart.beanfactory.Car;

 public class MyBeanPostProcessor implements BeanPostProcessor{

     public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {        
         if(beanName.equals("car")){
             Car car = (Car)bean;
             if(car.getMaxSpeed() >= 200){
                 System.out.println("调用MyBeanPostProcessor.postProcessAfterInitialization()，将maxSpeed调整为200。");
                 car.setMaxSpeed(200);
             }
         }
         return bean;

     }

     public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {        
         if(beanName.equals("car")){
             Car car = (Car)bean;
             if(car.getColor() == null){
                 System.out.println("调用MyBeanPostProcessor.postProcessBeforeInitialization()，color为空，设置为默认黑色。");
                 car.setColor("黑色");
             }
         }
         return bean;
     }
 }

  3. MyInstantiationAwareBeanPostProcessor

     ``` java
 package com.smart.beanfactory;

 import java.beans.PropertyDescriptor;

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

 public class MyInstantiationAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter{

     //在实例化之前调用
     public Object postProcessBeforeInstantiation(Class beanClass, String beanName) throws BeansException {
         if("car".equals(beanName)){
             System.out.println("MyInstantiationAwareBeanPostProcessor.postProcessBeforeInstantiation");            
         }        
         return null;
     }
     //在实例化后调用
     public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
         if("car".equals(beanName)){
         System.out.println("InstantiationAwareBeanPostProcessor.postProcessAfterInstantiation");
         }
         return true;
     }
     //接口方法：在调置某个属性时调用
     public PropertyValues postProcessPropertyValues(
             PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName)
             throws BeansException {
         if("car".equals(beanName)){
            System.out.println("InstantiationAwareBeanPostProcessor.postProcessPropertyValues");
         }
         return pvs;
     }

     public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
         return bean;
     }

     public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
         return bean;
     }
 }

 ```

  4. MainBeanFactory

     package com.smart.beanfactory;

 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;

 public class MainBeanFactory {

     private static void LifeCycleInBeanFactory(){

        //①下面两句装载配置文件并启动容器
        Resource res = new ClassPathResource("com/smart/beanfactory/beans.xml");

        BeanFactory bf= new DefaultListableBeanFactory();
        XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader((DefaultListableBeanFactory)bf);
        reader.loadBeanDefinitions(res);

        //②向容器中注册MyBeanPostProcessor后处理器
        ((ConfigurableBeanFactory)bf).addBeanPostProcessor(new MyBeanPostProcessor());

        //③向容器中注册MyInstantiationAwareBeanPostProcessor后处理器
        ((ConfigurableBeanFactory)bf).addBeanPostProcessor(
                new MyInstantiationAwareBeanPostProcessor());
        //④第一次从容器中获取car，将触发容器实例化该Bean，这将引发Bean生命周期方法的调用。
        Car car1 = (Car)bf.getBean("car");
        car1.introduce();
        car1.setColor("红色");

        //⑤第二次从容器中获取car，直接从缓存池中获取
        Car car2 = (Car)bf.getBean("car");

        //⑥查看car1和car2是否指向同一引用
        System.out.println("car1==car2:"+(car1==car2));
        //⑦关闭容器
        ((DefaultListableBeanFactory)bf).destroySingletons();

     }
     public static void main(String[] args) {
         LifeCycleInBeanFactory();
     }
 }

  5. bean.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" xmlns:p="http://www.springframework.org/schema/p"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-4.0.xsd">
     <bean id="car" class="com.smart.beanfactory.Car"
           init-method="myInit"
           destroy-method="myDestory"
           p:brand="红旗CA72"
           p:maxSpeed="200"/>

 </beans>

  6. 执行结果

     MyInstantiationAwareBeanPostProcessor.postProcessBeforeInstantiation
 调用Car()构造函数。
 InstantiationAwareBeanPostProcessor.postProcessAfterInstantiation
 InstantiationAwareBeanPostProcessor.postProcessPropertyValues
 调用setBrand()设置属性。
 调用BeanNameAware.setBeanName()。
 调用BeanFactoryAware.setBeanFactory()。
 调用MyBeanPostProcessor.postProcessBeforeInitialization()，color为空，设置为默认黑色。
 调用InitializingBean.afterPropertiesSet()。
 调用myInit()，将maxSpeed设置为240。
 调用MyBeanPostProcessor.postProcessAfterInitialization()，将maxSpeed调整为200。
 introduce:brand:红旗CA72/color:黑色/maxSpeed:200
 car1==car2:true
 调用DisposableBean.destory()。
 调用myDestroy()。

ApplicationContext

  1. Bean
    实现BeanFactoryAware, BeanNameAware, InitializingBean, DisposableBean, ApplicationContextAware接口。

     package com.smart.context;

 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;

 //管理Bean生命周期的4个接口
 public class Car implements BeanFactoryAware, BeanNameAware, InitializingBean, DisposableBean, ApplicationContextAware {
     private String brand;
     private String color;
     private int maxSpeed;
     private String name;
     private BeanFactory beanFactory;
     private String beanName;

     public Car() {
         System.out.println("调用Car()构造函数。");
     }

     public String getBrand() {
         return brand;
     }

     public void setBrand(String brand) {
         System.out.println("调用setBrand()设置属性。");
         this.brand = brand;
     }

     public String getColor() {
         return color;
     }
     public void setColor(String color) {
         this.color = color;
     }

     public int getMaxSpeed() {
         return maxSpeed;
     }

     public void setMaxSpeed(int maxSpeed) {
         this.maxSpeed = maxSpeed;
     }

     public void introduce(){
         System.out.println("introduce:"+this.toString());
     }

     public String toString() {
         return "brand:" + brand + "/color:" + color + "/maxSpeed:"+ maxSpeed;
     }

     // BeanFactoryAware接口方法
     public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
         System.out.println("调用BeanFactoryAware.setBeanFactory()。");
         this.beanFactory = beanFactory;
     }

     // BeanNameAware接口方法
     public void setBeanName(String beanName) {
         System.out.println("调用BeanNameAware.setBeanName()。");
         this.beanName = beanName;
     }

     // InitializingBean接口方法
     public void afterPropertiesSet() throws Exception {
         System.out.println("调用InitializingBean.afterPropertiesSet()。");
     }

     // DisposableBean接口方法
     public void destroy() throws Exception {
         System.out.println("调用DisposableBean.destory()。");
     }

     //通过<bean>的init-method属性指定初始化方法
     public void myInit() {        
         System.out.println("调用myInit()，将maxSpeed设置为240。");
         this.maxSpeed = 240;
     }
     //通过<bean>的destroy-method属性指定销毁的方法
     public void myDestory() {
         System.out.println("调用myDestroy()。");
     }

     public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
         System.out.println("调用setApplicationContext方法");
     }

 }

  2. MyBeanFactoryPostProcessor

     package com.smart.context;

 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

 public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor{

     public void postProcessBeanFactory(ConfigurableListableBeanFactory bf) throws BeansException {
         BeanDefinition bd = bf.getBeanDefinition("car");
         bd.getPropertyValues().addPropertyValue("brand", "奇瑞QQ");
         System.out.println("调用MyBeanFactoryPostProcessor.postProcessBeanFactory()！");
     }
 }

  3. MyBeanPostProcessor

     package com.smart.context;

 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 {        
         if(beanName.equals("car")){
             Car car = (Car)bean;
             if(car.getColor() == null){
                 System.out.println("调用MyBeanPostProcessor.postProcessBeforeInitialization()，color为空，设置为默认黑色。");
                 car.setColor("黑色");
             }
         }
         return bean;
     }
     public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {        
         if(beanName.equals("car")){
             Car car = (Car)bean;
             if(car.getMaxSpeed() >= 200){
                 System.out.println("调用MyBeanPostProcessor.postProcessAfterInitialization()，将maxSpeed调整为200。");
                 car.setMaxSpeed(200);
             }
         }
         return bean;
     }
 }

  4. MainApplicationContext

     package com.smart.context;

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

 public class MainApplicationContext {

      public static void main(String[] args) {
         AbstractApplicationContext ctx = new ClassPathXmlApplicationContext("com/smart/context/bean.xml");
         Car car =ctx.getBean("car",Car.class);
         Car car1 =ctx.getBean("car",Car.class);
         System.out.println("car == car1 : " + (car == car1));
         ctx.close();
     }
 }

  5. bean.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"
     xmlns:p="http://www.springframework.org/schema/p"
     xsi:schemaLocation="http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-4.0.xsd">
    <bean id="car" class="com.smart.context.Car" init-method="myInit" destroy-method="myDestory"
          p:brand="红旗CA72"
          p:maxSpeed="200"/>
    <bean id="myBeanPostProcessor" class="com.smart.context.MyBeanPostProcessor"></bean>     
    <bean id="myBeanFactoryPostProcessor" class="com.smart.context.MyBeanFactoryPostProcessor"></bean>     
 </beans>

  6. 执行结果

     调用MyBeanFactoryPostProcessor.postProcessBeanFactory()！
 调用Car()构造函数。
 调用setBrand()设置属性。
 调用BeanNameAware.setBeanName()。
 调用BeanFactoryAware.setBeanFactory()。
 调用setApplicationContext方法
 调用MyBeanPostProcessor.postProcessBeforeInitialization()，color为空，设置为默认黑色。
 调用InitializingBean.afterPropertiesSet()。
 调用myInit()，将maxSpeed设置为240。
 调用MyBeanPostProcessor.postProcessAfterInitialization()，将maxSpeed调整为200。
 car == car1 : true

 三月 19, 2018 12:13:40 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose
 信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@71be98f5: startup date [Mon Mar 19 00:13:39 CST 2018]; root of context hierarchy

 调用DisposableBean.destory()。
 调用myDestroy()。

代码GitHub

验证代码GitHub库：SpringBeanLifecycle
SpringBeanLifecycle

更多内容请访问：IT源点

注意：本文归作者所有，未经作者允许，不得转载

#BeanFactory #Bean #生命周期 #ApplicationConetxt
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