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();
    }
}