Spring Bean的生命周期

Spring Bean的生命周期

一、概述

二、注入单向对象引用属性时

2.1原理

注入单向对象引用属性时，从容器中 getBean 获取后通过 set 方法反射设置进去，如果容器中没有，则先创建被注入对象 Bean 实例（完成整个生命周期）后，在进行注入操作。

2.2实验

1.要注入的属性在要创建bean的前面

applicationContext.xml:

<beanclass="com.itheima.service.impl.UserServiceImpl2"id="userService"><property name="userDao"ref="userDao"/><property name="userName"value="MM"/></bean><bean id="userDao"class="com.itheima.dao.impl.UserDaoImpl"init-method="init"></bean>

测试：

packagecom.itheima.test;importcom.alibaba.druid.pool.DruidDataSource;importcom.itheima.beans.OthrerBean;importcom.itheima.beans.Xxxbean;importcom.itheima.dao.UserDao;importcom.itheima.dao.impl.UserDaoImpl;importcom.itheima.dao.personDao;importcom.itheima.service.UserService;importcom.mysql.jdbc.Connection;importorg.apache.ibatis.io.Resources;importorg.apache.ibatis.session.SqlSession;importorg.apache.ibatis.session.SqlSessionFactory;importorg.apache.ibatis.session.SqlSessionFactoryBuilder;importorg.springframework.beans.factory.config.BeanDefinition;importorg.springframework.beans.factory.support.DefaultListableBeanFactory;importorg.springframework.beans.factory.xml.XmlBeanDefinitionReader;importorg.springframework.context.ApplicationContext;importorg.springframework.context.support.ClassPathXmlApplicationContext;importjavax.xml.bind.annotation.XmlAccessOrder;importjava.io.IOException;importjava.io.InputStream;importjava.sql.DriverManager;publicclassBeanFactoryTest{publicstaticvoidmain(String[]args)throwsException{ApplicationContextapplicationContext=newClassPathXmlApplicationContext("applicationContext_beanfac.xml");UserServiceuserService=applicationContext.getBean(UserService.class);}}

结果：

直接从BeanDefinitionMap中拿了

2.要注入的属性在要创建bean的后面

applicationContext.xml:

<bean id="userDao"class="com.itheima.dao.impl.UserDaoImpl"init-method="init"></bean><beanclass="com.itheima.service.impl.UserServiceImpl2"id="userService"><property name="userDao"ref="userDao"/><property name="userName"value="MM"/></bean>

结果：

在创建userService发现需要userDao属性但是BeanDefinitionMap中没有，就停下来先创建userDao，然后再继续注册。

三、注入双向对象引用属性

源码流程（由于源码剖析较为繁琐，篇幅太大，所以在这里就没有过多的阐述了，不过下面的图片是较为详细的，可以依据下面的图片自行进行剖析）：

四、Aware接口

Aware接口在开发中虽然不常用，但是它的思想却经常用在很多框架进行底层注入bean，常用的Aware接口如下：

实验：

UserServiceImpl：

packagecom.itheima.service.impl;importcom.itheima.dao.UserDao;importcom.itheima.service.UserService;importorg.springframework.beans.BeansException;importorg.springframework.beans.factory.BeanFactory;importorg.springframework.beans.factory.BeanFactoryAware;importorg.springframework.beans.factory.BeanNameAware;importorg.springframework.context.ApplicationContext;importorg.springframework.context.ApplicationContextAware;importorg.springframework.web.context.ServletContextAware;importjavax.servlet.ServletContext;importjava.util.List;importjava.util.Map;importjava.util.Properties;importjava.util.Set;//@Service("userService")publicclassUserServiceImpl2implementsUserService,ServletContextAware,BeanFactoryAware,ApplicationContextAware,BeanNameAware{@Overridepublicvoidshow2(){// 打印集合// System.out.println(userDaoList);// System.out.println(stringList);// 打印集合// System.out.println(userDaoSet);//// 打印集合// System.out.println(stringSet);// System.out.println(userDaoMap);// System.out.println(properties);System.out.println(userDao);}@Overridepublicvoidshow1(){// 打印集合}publicUserServiceImpl2(){// System.out.println("userService已经加载，已执行构造函数");}privateUserDaouserDao;publicvoidsetUserDao(UserDaouserDao){// System.out.println("userServerce执行注入UserDao的操作，即执行set方法");this.userDao=userDao;}@OverridepublicvoidsetBeanFactory(BeanFactorybeanFactory)throwsBeansException{System.out.println(beanFactory);}@OverridepublicvoidsetBeanName(Strings){System.out.println(s);}@OverridepublicvoidsetApplicationContext(ApplicationContextapplicationContext)throwsBeansException{System.out.println(applicationContext);}@OverridepublicvoidsetServletContext(ServletContextservletContext){System.out.println(servletContext);}}

测试：

packagecom.itheima.test;importcom.alibaba.druid.pool.DruidDataSource;importcom.itheima.beans.OthrerBean;importcom.itheima.beans.Xxxbean;importcom.itheima.dao.UserDao;importcom.itheima.dao.impl.UserDaoImpl;importcom.itheima.dao.personDao;importcom.itheima.service.UserService;importcom.mysql.jdbc.Connection;importorg.apache.ibatis.io.Resources;importorg.apache.ibatis.session.SqlSession;importorg.apache.ibatis.session.SqlSessionFactory;importorg.apache.ibatis.session.SqlSessionFactoryBuilder;importorg.springframework.beans.factory.config.BeanDefinition;importorg.springframework.beans.factory.support.DefaultListableBeanFactory;importorg.springframework.beans.factory.xml.XmlBeanDefinitionReader;importorg.springframework.context.ApplicationContext;importorg.springframework.context.support.ClassPathXmlApplicationContext;importjavax.xml.bind.annotation.XmlAccessOrder;importjava.io.IOException;importjava.io.InputStream;importjava.sql.DriverManager;publicclassBeanFactoryTest{publicstaticvoidmain(String[]args)throwsException{ApplicationContextapplicationContext=newClassPathXmlApplicationContext("applicationContext_beanfac.xml");UserServiceuserService=applicationContext.getBean(UserService.class);}}

结果：

由于是没有配置web环境，所以servletContext没有打印出来。