spring中ref标签的用法

1、作用

将对象值注入到对应的属性，依赖于配置标签实现

2、属性

bean：通过该属性可以引用同一容器或父容器中的bean对象
parent：引用父容器中的bean

3、用法

bean属性用法比较简单，这里就不再介绍，主要讲一下parent属性的用法

前提

一个Boss类中有name，Car属性，对应一个BossBean.xml配置文件
一个Car类中有brand、price、color属性，对应一个CarBean.xml配置文件

需求

在BossBean.xml配置文件中引用CarBean.xml配置文件的bean

Boos类

package com.yl.bean;

public class Boss {
    private String name;
    private Car car;

    public Boss() {
    }

    public Boss(String name, Car car) {
        this.name = name;
        this.car = car;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Car getCar() {
        return car;
    }

    public void setCar(Car car) {
        this.car = car;
    }
}

Car类

package com.yl.bean;

public class Car {
    private String brand;
    private Integer price;
    private String color;

    public Car() {
    }

    public Car(String brand, Integer price, String color) {
        this.brand = brand;
        this.price = price;
        this.color = color;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }

    public Integer getPrice() {
        return price;
    }

    public void setPrice(Integer price) {
        this.price = price;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }
}

BossBean.xml配置文件（父容器）

<?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">

    <!--Boss-->
    <bean id="boss" class="com.yl.bean.Boss">
        <property name="name" value="yl001"></property>
        
        <property name="car">
            <!--引用父容器中的car-->
            <ref parent="car"></ref>
        </property>
    </bean>

</beans>

CarBean.xml配置文件（子容器）

<?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">

    <!--Car-->
    <bean id="car" class="com.yl.bean.Car">
        <property name="brand" value="兰博基尼"></property>
        <property name="color" value="红色"></property>
        <property name="price" value="1000000"></property>
    </bean>

</beans>

4、测试类

 public static void main(String[] args) {
        //父容器 (CarBean)
        ApplicationContext parentCtx=new ClassPathXmlApplicationContext("CarBean.xml");
        //子容器(BoosBean)关联父容器
        ApplicationContext childCtx=new ClassPathXmlApplicationContext(new String[] {"BossBean.xml"},parentCtx);

        Boss boss= (Boss) childCtx.getBean("boss");
        System.out.println("老板名 ="+boss.getName());
        System.out.println("所用的车 ="+boss.getCar().getBrand());
    }

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