什么是自动装配

根据指定的装配规则（属性名称或者属性类型），Spring自动将匹配的属性值进行注入

前面使用的装配方式都是手动装配

package com.test3;

public class Emp {
    private String name;
    private Dpt dpt;

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

    public void setDpt(Dpt dpt) {
        this.dpt = dpt;
    }

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

    public void test(){
        System.out.println(dpt);
    }
}

package com.test3;

public class Dpt {
    private String name;

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

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

<?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="emp" class="com.test3.Emp">
        <property name="dpt" ref="dpt"/>
    </bean>
    <bean id="dpt" class="com.test3.Dpt"/>
</beans>

package com.test3;

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

import static org.junit.Assert.*;

public class EmpTest {

    @Test
    public void test1() {
        ApplicationContext context = new ClassPathXmlApplicationContext("spring9.xml");
        Emp emp = context.getBean("emp", Emp.class);
        System.out.println("emp = " + emp);
    }
}

演示自动装配

<?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">
    <!--
        实现自动装配
        bean标签有一个属性autowire，配置自动装配
        autowire属性有两个常用的值：
            byName 根据属性名称注入
                注入的bean的id值和类属性名称一致
            byType 根据属性类型注入
                注入的bean的class不能相同
    -->
    <!--<bean id="emp" class="com.test3.Emp" autowire="byName">
        <property name="dpt" ref="dpt"/>
    </bean>-->
    <bean id="emp" class="com.test3.Emp" autowire="byType">
        <!--<property name="dpt" ref="dpt"/>-->
    </bean>
    <bean id="dpt" class="com.test3.Dpt"/>
</beans>