spring原理

1、spring框架什么时候被加载？

（1）ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml")执行的时候，

spring容器对象被创建。

（2）同时，applicationContext.xml里面配置的对象被创建到内存中。（内存模型类似于HashMap）。容器利用反射机制创建bean的实例。如下图

2、spring中配置的bean怎样被创建？

3、bean与bean之间的关系怎样维护？

代码结构图：

applicationContext代码

 <?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.spring.service.SpringService" id="springService">
     <property name="userName" value="lvyf"/>
     <property name="tService" ref="testService"></property>
 </bean>

 <bean class="com.spring.service.TestService" id="testService">
     <property name="pwd" value="123456"/>
 </bean>
 </beans>

SpringService代码

 package com.spring.service;

 public class SpringService {
     private String userName;

     private TestService tService;

     public TestService gettService() {
         return tService;
     }

     public void settService(TestService tService) {
         this.tService = tService;
     }

     public String getUserName() {
         return userName;
     }

     public void setUserName(String userName) {
         this.userName = userName;
     }

     public void sayHello() {
         System.out.println("hello world " + userName);
         tService.getPasswd();
     }

 }

TestService代码

 package com.spring.service;

 public class TestService {
     private String pwd;

     public String getPwd() {
         return pwd;
     }

     public void setPwd(String pwd) {
         this.pwd = pwd;
     }

     public void getPasswd(){
         System.out.println(pwd);
     }
 }

Run代码

 package com.run;

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

 import com.spring.service.SpringService;

 public class Run {

     public static void testRun(){
         //1、创建spring的IOC容器对象
         @SuppressWarnings("resource")
         ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext-bean.xml");
         //2、从IOC容器获取spring bean实例
         //SpringService sService = (SpringService)ac.getBean("springService");
         SpringService sService = (SpringService)ac.getBean(SpringService.class);
         //3、调用sayHello方法
         sService.sayHello();
     }

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