Spring 的DI 依赖注入

UserDao.java

package com.atguigu.Ioc_02;

public class UserDao {
}

UserService.java

package com.atguigu.Ioc_02;

public class UserService {
    private UserDao userDao;

    private int age;
    private String name;

    public UserService(UserDao userDao){
        this.userDao = userDao;
    }

    public UserService(int age, String name, UserDao userDao){
        this.age = age;
        this.name = name;
        this.userDao = userDao;
    }
}

MovieFinder.java

package com.atguigu.Ioc_02;

public class MovieFinder {
}

SimpleMovieLister.java

package com.atguigu.Ioc_02;

public class SimpleMovieLister {
    private MovieFinder movieFinder;

    private String movieName;

    public void setMovieFinder(MovieFinder movieFinder){
        this.movieFinder = movieFinder;
    }

    public void setMovieName(String movieName){
        this.movieName = movieName;
    }
}

resources文件夹下的 xml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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    引用 和 被引用的组件，必须全部在Ioc容器中，不能乡愁

 	springIoc是一个高级容器，内部会有缓存动作，
         1、先创建对象（Ioc）
         2、再进行属性赋值（DI）


    1、单个构造函数参数注入
    <bean id="userDao" class="com.atguigu.Ioc_02.UserDao" />
    <bean id="userService" class="com.atguigu.Ioc_02.UserService">
        <!--
            <constructor-arg：构造函数传值 DI的配置
                value = 直接属性值(String name = "二狗子"，int age = 18)
                ref = 其他bean的Id
        -->
        <constructor-arg ref="userDao"/>
    </bean>

    2、多个构造函数参数注入
    <bean id="userService1" class="com.atguigu.Ioc_02.UserService">
        方案1：按照，构造函数参数的顺序，填写值
        <constructor-arg value="18"/>
        <constructor-arg value="二狗子"/>
        <constructor-arg ref="userDao"/>
    </bean>

    <bean id="userService2" class="com.atguigu.Ioc_02.UserService">
        方案2：按照，构造函数参数的名字(name=构造参数的参数名)，填写值
        <constructor-arg name="age" value="18"/>
        <constructor-arg name="name" value="二狗子"/>
        <constructor-arg name="userDao" ref="userDao"/>
    </bean>

    <bean id="userService3" class="com.atguigu.Ioc_02.UserService">
        方案3：按照，构造函数参数的下角标（从左到右，从0开始），填写值
                因为，public UserService(int age, String name, UserDao userDao)
                所以，age的下角标是0，name的下角标是1，userDao的下角标是2
        <constructor-arg index="0" value="18"/>
        <constructor-arg index="1" value="二狗子"/>
        <constructor-arg index="2" ref="userDao"/>
    </bean>

    3、触发setter方法，进行依赖注入
    <bean id="movieFinder" class="com.atguigu.Ioc_02.MovieFinder"/>
    <bean id="simpleMovieLister" class="com.atguigu.Ioc_02.SimpleMovieLister">
        name: 属性名（setter方法的 去掉“set”和首字母小写的值）
                如：public void setMovieFinder(MovieFinder movieFinder)
                此时，name = movieFinder

             value=“直接属性值” 和 ref=“其他bean的Id”，
             value、ref这两二选一
        <property name="movieFinder" ref="movieFinder"></property>
        <property name="movieName" value="西红柿首富"></property>
    </bean>


</beans>