Bean的自动装配

环境搭建：一个人有两个宠物

1. Dog.java

public class Dog {
    public void bark(){
        System.out.println("miao");
    }
}

2. Cat.java

public class Cat {
    public void bark(){
        System.out.println("wang");
    }
}

3. Person.java

public class Person {

    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;
    }

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

4.beans.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/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="cat" class="com.zhoutianhao.pojo.Cat"/>
    <bean id="dog" class="com.zhoutianhao.pojo.Dog"/>

    <bean id="person" class="com.zhoutianhao.pojo.Person">
        <property name="name" value="zhoutianhao"/>
        <property name="dog" ref="dog"/>
        <property name="cat" ref="cat"/>
    </bean>
</beans>

5. MyTest.java

public class MyTest {
    @Test
    public void test1(){
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");

        Person person = context.getBean("person", Person.class);
        person.getDog().bark();
        person.getCat().bark();
    }
}

byName自动装配

    <bean id="cat" class="com.zhoutianhao.pojo.Cat"/>
    <bean id="dog" class="com.zhoutianhao.pojo.Dog"/>
    
    <!--
    byName : 会自动在容器上下文中查找，和自己对象set方法后面的值对应的 beanid
    -->
    <bean id="person" class="com.zhoutianhao.pojo.Person" autowire="byName">
        <property name="name" value="周天豪"/>
    </bean>

byType自动装配

    <bean id="cat" class="com.zhoutianhao.pojo.Cat"/>
    <bean id="dog1121" class="com.zhoutianhao.pojo.Dog"/>
    
    <!--
    byType : 会自动在容器上下文中查找，和自己对象属性类型相同的bean
    -->
    <bean id="person" class="com.zhoutianhao.pojo.Person" autowire="byType">
        <property name="name" value="周天豪"/>
    </bean>

小结

• byName：需要保证所有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的类型一致！