目录结构

导入pom.xml依赖包

 <dependencies><!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc --><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>5.2.0.RELEASE</version></dependency><!--        aop--><!-- https://mvnrepository.com/artifact/org.aspectj/aspectjweaver --><dependency><groupId>org.aspectj</groupId><artifactId>aspectjweaver</artifactId><version>1.9.19</version><scope>runtime</scope></dependency><!-- https://mvnrepository.com/artifact/junit/junit --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.13.2</version><scope>test</scope></dependency></dependencies>

People类，人可以有多个宠物

package com.qing;public class People {private Cat cat;private Dog dog;private String name;public Cat getCat() {return cat;}public void setCat(Cat cat) {this.cat = cat;}public Dog getDog() {return dog;}public void setDog(Dog dog) {this.dog = dog;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic String toString() {return "People{" +"cat=" + cat +", dog=" + dog +", name='" + name + '\'' +'}';}
}

Cat类

package com.qing;public class Cat {public void shout(){System.out.println("喵");}
}

Dog类

package com.qing;public class Dog {public void shout(){System.out.println("汪");}
}

applicationContext.xml

<?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/beanshttps://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="cat" class="com.qing.Cat"></bean><bean id="dog" class="com.qing.Dog"></bean><bean id="people" class="com.qing.People"><property name="name" value="你好呀"></property><property name="cat" ref="cat"></property><property name="dog" ref="dog"></property></bean></beans>

测试代码

import com.qing.People;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;public class MyTest {@Testpublic void test(){ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");People people = context.getBean("people", People.class);people.getDog().shout();people.getCat().shout();}
}

byName自动装配

 byName：会自动在容器上下文查找，和自己这个对象的set方法后面值对应的bean中的id

如果id不满足对象的名字，则会报错；例如：dog222不满足对象的id名字

byType自动装配

 byType：会自动在容器上下文中查找，和自己对象属性相同的bean，可以省略id

不能有两个一样的id，属性名可以不同

注解实现自动装配

导入约束，并开启注解的支持

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beanshttps://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttps://www.springframework.org/schema/context/spring-context.xsd"><bean id="cat" class="com.qing.Cat"></bean><bean id="dog" class="com.qing.Dog"></bean><bean id="people" class="com.qing.People"></bean>
<!--    开启注解的支持--><context:annotation-config/></beans>

在属性上配置注解

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

 如果@Autowired自动装配的环境比较复杂，自动装配无法通过一个注解@Autowired完成的时候，我们可以使用@Qualifier(value="xxx")去配置@Autowired的使用，指定一个唯一的bean对象注入

总结：

• byname需要保证所有的bean的id唯一，并且这个bean需要和自动注入的属性的set方法的值一致
• bytype需要保证所有bean的class唯一，并且这个bean需要和自动注入的属性类型一致

所有的类都需装入spring里面，所有的bean都需要去容器去获取，容器获取的bean是一个对象