Spring学习02——控制反转、依赖注入

有两个人，张三和李四

package com.su.service;

public class ZhangSan implements Tester{
    
    public void test(){
        System.out.println("张三-测试程序");
    }
}

package com.su.service;

public class Lisi implements Tester{
    
    public void test(){
        System.out.println("李四-测试程序");
    }
}

有一个Tester接口，张三和李四都实现了这个接口

package com.su.service;

public interface Tester {
    public void test();
}

测试工作类

package com.su.service;

public class JavaWork {
    
    private Tester tester;
    
    public void setTester(Tester tester) {
        this.tester = tester;
    }



    public void doTest(){
//        ZhangSan zhangsan=new ZhangSan();
//        zhangsan.test();
        tester.test();
    }
}

主管负责分配谁去测试（通过setTester，即控制权交给主管，而非每次换人去测试，都要在JavaWork的doTest类中new出人，这就是控制反转）

package com.su.test;

import com.su.service.JavaWork;
import com.su.service.Lisi;

public class Test {
    /**
     * 主管执行命令
     */
    public static void main(String[] args) {
        JavaWork javaWork=new JavaWork();
//        javaWork.setTester(new ZhangSan());
        javaWork.setTester(new Lisi());
        javaWork.doTest();
    }
}

而spring帮助我们做的就是这个，在xml文件中通过配置(spring管理bean)，分配测试人员

<?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 id="zhangsan" class="com.su.service.ZhangSan"></bean>
  
    <bean id="lisi" class="com.su.service.Lisi"></bean>
  
    <bean id="javaWork" class="com.su.service.JavaWork">
        <property name="tester" ref="lisi"></property>
    </bean>
  
</beans>

package com.su.test;

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

import com.su.service.JavaWork;

public class Test2 {
    public static void main(String[] args) {
        ApplicationContext ac=new ClassPathXmlApplicationContext("beans.xml");
        JavaWork javaWork=(JavaWork)ac.getBean("javaWork");
        javaWork.doTest();
    }
}