概述

自动装配是Spring满足bean依赖一种方式，Spring会在上下文中自动寻找，并自动给bean装配属性

自动装配有两种方式：

  1. ByName

    根据Setter方法名指定自动装配的bean的id，例如：Setter的方法名为setDog1，所以bean的id就必须为dog1

  2. ByType

    需要保证所有bean的class唯一，即不可以存在相同类型的bean

代码实现

测试环境

一个People有Dog和Cat

手动装配

People实体类

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package com.ledao.entity;

/**
 * @author LeDao
 * @company
 * @create 2022-02-15 18:13
 */
public class People {

    private String name;
    private Dog dog;
    private Cat cat;

    public String getName() {
        return name;
    }

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

    public Dog getDog() {
        return dog;
    }

    public void setDog(Dog dog) {
        this.dog = dog;
    }

    public Cat getCat() {
        return cat;
    }

    public void setCat(Cat cat) {
        this.cat = cat;
    }

    @Override
    public String toString() {
        return "People{" +
                "name='" + name + '\'' +
                ", dog=" + dog +
                ", cat=" + cat +
                '}';
    }
}

Dog实体类

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package com.ledao.entity;

/**
 * @author LeDao
 * @company
 * @create 2022-02-15 18:14
 */
public class Dog {

    private String name;

    public Dog() {
        System.out.println("狗吃骨头");
    }

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "Dog{" +
                "name='" + name + '\'' +
                '}';
    }
}

Cat实体类

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package com.ledao.entity;

/**
 * @author LeDao
 * @company
 * @create 2022-02-15 18:14
 */
public class Cat {

    private String name;

    public Cat() {
        System.out.println("猫吃鱼");
    }

    public String getName() {
        return name;
    }

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

    @Override
    public String toString() {
        return "Dog{" +
                "name='" + name + '\'' +
                '}';
    }
}

ApplicationContext.xml

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<?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="dog" class="com.ledao.entity.Dog">
        <property name="name" value="小花"/>
    </bean>

    <bean id="cat" class="com.ledao.entity.Cat">
        <property name="name" value="小哈"/>
    </bean>

    <bean id="people" class="com.ledao.entity.People">
        <property name="name" value="小明"/>
        <property name="dog" ref="dog"/>
        <property name="cat" ref="cat"/>
    </bean>
</beans>

测试代码

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import com.ledao.entity.People;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author LeDao
 * @company
 * @create 2022-02-12 15:56
 */
public class MyTest {

    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("ApplicationContext.xml");
        People people = context.getBean("people", People.class);
        System.out.println(people);
    }
}

结果

image-20220215192042401

自动装配

ByName方式

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<?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="dog" class="com.ledao.entity.Dog">
        <property name="name" value="小哈1"/>
    </bean>
    <bean id="dog2" class="com.ledao.entity.Dog">
        <property name="name" value="小哈2"/>
    </bean>
    <bean id="cat" class="com.ledao.entity.Cat">
        <property name="name" value="小花1"/>
    </bean>

    <bean id="people" class="com.ledao.entity.People" autowire="byName">
        <property name="name" value="tom"/>
    </bean>
</beans>

ByType方式

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<?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="dog1" class="com.ledao.entity.Dog">
        <property name="name" value="小哈1"/>
    </bean>
    <bean id="cat" class="com.ledao.entity.Cat">
        <property name="name" value="小花1"/>
    </bean>

    <bean id="people" class="com.ledao.entity.People" autowire="byType">
        <property name="name" value="tom"/>
    </bean>
</beans>