【尚硅谷】spring学习笔记（12）：在 classpath 中扫描组件

组件扫描(component scanning): Spring 能够从 classpath 下自动扫描, 侦测和实例化具有特定注解的组件.

特定组件包括:

@Component: 基本注解, 标识了一个受 Spring 管理的组件
@Respository: 标识持久层组件
@Service: 标识服务层(业务层)组件
@Controller: 标识表现层组件

对于扫描到的组件, Spring 有默认的命名策略: 使用非限定类名, 第一个字母小写. 也可以在注解中通过 value 属性值标识组件的名称

当在组件类上使用了特定的注解之后, 还需要在 Spring 的配置文件中声明 <context:component-scan> ：
base-package 属性指定一个需要扫描的基类包，Spring 容器将会扫描这个基类包里及其子包中的所有类.
当需要扫描多个包时, 可以使用逗号分隔.
如果仅希望扫描特定的类而非基包下的所有类，可使用 resource-pattern 属性过滤特定的类，示例：

<context:include-filter> 子节点表示要包含的目标类
<context:exclude-filter> 子节点表示要排除在外的目标类
<context:component-scan> 下可以拥有若干个 <context:include-filter> 和 <context:exclude-filter> 子节点

<context:include-filter> 和 <context:exclude-filter> 子节点支持多种类型的过滤表达式：

package com.atguigu.spring.beans.annotation;

import org.springframework.stereotype.Component;

@Component
public class TestObject {

}

package com.atguigu.spring.beans.annotation.controller;

import org.springframework.stereotype.Controller;

@Controller
public class UserController {
	public void execute() {
		System.out.println("UserController execute...");
	}

}

package com.atguigu.spring.beans.annotation.repository;

public interface UserRepository {
   void save();
}

package com.atguigu.spring.beans.annotation.repository;

import org.springframework.stereotype.Repository;

@Repository("userRepository")
public class UserRepositoryImpl implements UserRepository {

	@Override
	public void save() {
		System.out.println("UserRepository Save...");
	}
}

package com.atguigu.spring.beans.annotation.service;

import org.springframework.stereotype.Service;

@Service("userService")
public class UserService {
	
	public void add() {
		System.out.println("UserService add...");
	}
	
}

<?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-4.0.xsd">

    <!-- 指定Spring IOC 容器扫描的包 -->
   <!-- <context:component-scan base-package="com.atguigu.spring.beans.annotation"></context:component-scan> --> 
   <!-- <context:component-scan 
               base-package="com.atguigu.spring.beans.annotation"
               resource-pattern="repository/*.class"></context:component-scan>-->
               
    <!--<context:component-scan base-package="com.atguigu.spring.beans.annotation">
             <context:exclude-filter type="annotation" 
             expression="org.springframework.stereotype.Repository"/>
        </context:component-scan>-->
        
    <!-- <context:component-scan base-package="com.atguigu.spring.beans.annotation" use-default-filters="false">
             <context:include-filter type="annotation" 
             expression="org.springframework.stereotype.Repository"/>
        </context:component-scan> -->
        
     <!-- <context:component-scan base-package="com.atguigu.spring.beans.annotation" >
             <context:exclude-filter type="assignable" 
             expression="com.atguigu.spring.beans.annotation.repository.UserRepository"/>
        </context:component-scan> -->
        
          <context:component-scan base-package="com.atguigu.spring.beans.annotation" use-default-filters="false">
             <context:include-filter type="assignable" 
             expression="com.atguigu.spring.beans.annotation.repository.UserRepository"/>
        </context:component-scan> 
</beans>

package com.atguigu.spring.beans.annotation;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


import com.atguigu.spring.beans.annotation.controller.UserController;
import com.atguigu.spring.beans.annotation.repository.UserRepository;
import com.atguigu.spring.beans.annotation.service.UserService;

public class Main {
	public static void main(String[] args) {
		ApplicationContext apl = new ClassPathXmlApplicationContext("beans-annotation.xml");
//		TestObject to = (TestObject) apl.getBean("testObject");
//		System.out.println(to);
//		
//		UserController userController = (UserController) apl.getBean("userController");
//		System.out.println(userController);
//		
//		UserService userService = (UserService) apl.getBean("userService");
//		System.out.println(userService);
		
		UserRepository userRepository = (UserRepository) apl.getBean("userRepository");
		System.out.println(userRepository);
	}

}

结果：

六月 14, 2018 6:26:15 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@6193b845: startup date [Thu Jun 14 18:26:15 CST 2018]; root of context hierarchy
六月 14, 2018 6:26:16 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [beans-annotation.xml]
com.atguigu.spring.beans.annotation.repository.UserRepositoryImpl@2f943d71

【尚硅谷】spring学习笔记（12）：在 classpath 中扫描组件

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