Spring bean的生命周期详解

bean的生命周期
1.实例化bean 即new
2.按照spring上下文对实例化的bean进行配置 即填充属性，也就是IOC/DI（控制反转，依赖注入）
3.如果这个bean实现了BeanNameAware接口，Spring会调用它实现的setBeanName()方法，参数是bean的ID,即Spring将bean的ID传递给setBeanName()方法。（让bean知道自己是谁，即自己的ID）
4.如果bean实现了BeanFactoryAware接口，Spring将调用setBeanFactory(BeanFactory factory)方法，将BeanFactory容器实例传入;(即知道bean自己属于哪个工厂)
5.如果Bean实现了ApplicationContextAware接口，Spring将调用setApplicationContext(ApplicationContext context)方法,传入Spring上下文。
6.如果Bean实现了BeanPostProcessor接口，将会调用postProcessBeforeInialization(Object obj,String s)方法。BeanPostProcessor经常被用作是Bean内容的更改。
7.如果这个Bean在Spring配置文件中配置了init-method属性会自动调用其配置的初始化方法。
8.如果这个Bean实现了BeanPostProcessor接口，将会调用postAfterInitialization(Object obj,String s)方法
备注：当以上工作完成后就可以使用这个Bean了，这个bean是single的，一般调用同一个ID的bean会是在内容地址相同的实例
9.这个Bean会一直留在应用上下文中（ApplicationContext），直到该应用上下文被销毁。
10.如果这个Bean实现了DisposableBean接口，会调用destroy()方法；如果Bean在Spring配置中配置了destroy-method属性，会自动调用其配置的销毁方法。

在Spring框架中，bean的定义，从编写到配置再到最终的getbean调用，框架都有相应的实现规则，具体如下所述。

bean的定义：

 package com.spring.beans;

 import javax.ejb.Init;

 import org.springframework.beans.factory.InitializingBean;

 public class HelloBean implements InitializingBean {

     public HelloBean() {
         System.out.println("构造方法");
     }

     private String name;
     private String nullTest;

     private int age;

     public String getNullTest() {
         return nullTest;
     }

     public void setNullTest(String nullTest) {
         this.nullTest = nullTest;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public int getAge() {
         return age;
     }

     public void setAge(int age) {
         this.age = age;
     }

     public void prints(String str) {
         System.out.println(str + ":hahahah");
     }

     public void init() {
         System.out.println("init");
     }

     @Override
     public void afterPropertiesSet() throws Exception {
         // TODO Auto-generated method stub
         System.out.println("initializing");
     }
 }

BeanPostProcessor定义:

 package com.spring.test;

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

 public class BeanPostProcessor_Imp implements BeanPostProcessor {

     @Override
     public Object postProcessAfterInitialization(Object arg0, String arg1)
             throws BeansException {
         System.out.println("执行后");
         return arg0;
     }

     @Override
     public Object postProcessBeforeInitialization(Object arg0, String arg1)
             throws BeansException {
         System.out.println("执行前");
         return arg0;
     }

 }

测试类的定义：

 package com.spring.test;

 import java.util.List;

 import org.springframework.context.ApplicationContext;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.Resource;

 import com.spring.beans.BigBearBean;
 import com.spring.beans.HelloBean;
 import com.spring.beans.List_Map_Bean;
 import com.spring.beans.smallBearBean;
 import com.spring.interfaces.Animal;

 public class HelloTest {
     public static void main(String[] args) {
         ApplicationContext ctx = new ClassPathXmlApplicationContext(
                 "hellotest.xml");
         HelloBean HB = (HelloBean) ctx.getBean("hello");
         HB.prints("王涛");
         System.out.println(HB.getName() + "\n------------");
     }

 }

配置文件：

 <?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:util="http://www.springframework.org/schema/util"
     xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
     xmlns:p="http://www.springframework.org/schema/p"
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
         http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd
         http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
         http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

     <bean id="hello" class="com.spring.beans.HelloBean" init-method="init">
         <property name="name">
             <value><![CDATA[<wb<t>]]></value>
         </property>
         <property name="age" value="23" />
         <property name="nullTest">
             <value></value>
         </property>
     </bean>
     <bean class="com.spring.test.BeanPostProcessor_Imp"></bean>
 </beans>

运行结果：

 15:38:12,269 INFO  [context.support.ClassPathXmlApplicationContext] Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@61a48515: startup date [Fri Jun 23 15:38:12 CST 2017]; root of context hierarchy
 15:38:12,343 INFO  [factory.xml.XmlBeanDefinitionReader] Loading XML bean definitions from class path resource [hellotest.xml]
 15:38:12,588 INFO  [factory.support.DefaultListableBeanFactory] Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@25ff3700: defining beans [hello,com.spring.test.BeanPostProcessor_Imp#0]; root of factory hierarchy
 构造方法
 执行前
 initializing
 init
 执行后
 王涛:hahahah