【Spring】@Component组件

大前提：

添加了相关的约束文件以及注解支持

<?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/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
             http://www.springframework.org/schema/context
             http://www.springframework.org/schema/context/spring-context.xsd">


    <context:annotation-config/>




</beans>

package org.example.eneity;


import org.springframework.stereotype.Component;

@Component
public class User {
    public String name="张三";

}

public String name=" 张三 ”可以如下这么写

package org.example.entity;


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

@Component
public class User {
    @Value("张三")
    public String name;

}

@Componen注解的作用相当于创建了一个bean

@Component = <bean id =" user " class=" org.example.eneity.User " />

beans.xml

<context:component-scan base-package="org.example.entity"/>

它的作用是：指定扫描这个包，在这个包下的注解会生效

测试


public class Test10 {
    public static void main(String[] args) {
    ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
    User user=(User) context.getBean("user");
        System.out.println(user.name);
    }
}