三种装配Bean

1、在xml中显式装配在之前的配置都是用xml显式装配
2、在java中显式装配
3、隐式的自动装配bean

环境搭建

实体类

package com.my.pojo;

public class Cat {
    
    
    public void shout(){
    
    
        System.out.println("miaomiao");
    }
}

public class Dog {
    
    
    public void shout(){
    
    
        System.out.println("wangwang");
    }
}


package com.my.pojo;

public class People {
    
    

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

    public String getName() {
    
    
        return name;
    }

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

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

配置

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

    <bean id="people" class="com.my.pojo.People">
        <property name="name" value="奥特曼"/>
        <property name="dog" ref="dog"/>
        <property name="cat" ref="cat"/>
    </bean>

</beans>

测试运行


import com.my.pojo.People;
import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    
    
    @Test
    public void test(){
    
    
        ApplicationContext context =  new ClassPathXmlApplicationContext("beans.xml");
        People people = context.getBean("people", People.class);
        people.getDog().shout();
        people.getCat().shout();
    }
}

wangwang
miaomiao

java中显式装配

完全不使用Spring配置，全权交给java实现
JavaConfig是Spring的一个子项目：在Spring4之后成为一个核心功能
在这里插入图片描述

package com.my.pojo;


import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;


// 等价于在配置文件中的<bean id="user" class="com.my.pojo.User"/>
@Component
public class User {
    
    
    @Value("lalalala")
    public String name ;

}


package com.my.config;


import com.my.pojo.User;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MyConfig {
    
    

    @Bean
    public User getUser(){
    
    
        return new User();
    }

}


import com.my.config.MyConfig;
import com.my.pojo.User;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class MyTest {
    
    
    @Test
    public void Test(){
    
    
        ApplicationContext context =  new AnnotationConfigApplicationContext(MyConfig.class);
        User user = (User) context.getBean("getUser");
        System.out.println(user.getName());

    }
}