Spring容器类扫描注解_spring 扫描容器-优快云博客

1、component

package Class_Scan_Annotation;

import org.springframework.stereotype.Component;

import javax.annotation.Resource;

/**
 * Created by Administrator on 2019/6/1.
 */

@Component("person")
public class Person {
    @Resource(name = "student")
//    @Autowired 按照类型匹配
//    @Qualifier("student") 按照name匹配
    private Student student;

    public Student getStudent() {
        return student;
    }
}

2、component

package Class_Scan_Annotation;

import org.springframework.stereotype.Component;

/**
 * Created by Administrator on 2019/5/29.
 */
@Component("student")
public class Student {
    public void say() {
        System.out.println("你好学生！");
    }
}

3、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"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">
    <!--
        component:把一个类放入到Spring容器中，该类就是一个component
        在base-package指定的包及子包下 扫描 所有的类
    -->
    <context:component-scan base-package="Class_Scan_Annotation"></context:component-scan>
</beans>

4、单元测试

package Class_Scan_Annotation;

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

public class AnnotationTest {
    @Test
    public void testAnnotation() {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("Class_Scan_Annotation/DI_Annotation.xml");
        Person person = (Person) context.getBean("person");
        person.getStudent().say();
    }
}

5、输出
学生你好
6、原理

* 原理
 * 1、启动spring容器，spring容器解析配置文件
 * 2、当解析到 <context:component-scan base-package="Class_Scan_Annotation"></context:component-scan>
 *      就会在上面指定的包及子包中扫描所有的类，看那些类上面有@component注解
 * 3、如果有component注解，则由如下的规则
 *          @component
 *          public class PersionDaoImpl{
 *
 *          }
 *          ==
 *          <bean id="persionDaoImpl" class ="XXXX"></bean>
 *          id的值，把类的第一个字母变成小写，其他的字母不变
 *           @component(name="persionDao")
 *          public class PersionDaoImpl{
 *
 *          }
 *          ==
 *          <bean id="persionDao" class ="XXXX"></bean>