基于注解的方式装配bean

<?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">

	<!-- 开启注解扫描 -->
	<context:component-scan base-package="com.learn.spring" ></context:component-scan>

</beans>

package com.learn.spring.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;

import com.learn.spring.service.UserService;

/**
 * 表现层的组件
 * 
 * @Controller的作用:
 * 	  等价于在xml配置文件中: <bean id="userController" class="com.learn.spring.controller.UserController"></bean>
 * @Controller注解默认的id值是类名首字母小写,如果想要自己指定，可以使用value属性来指定
 * @Controller(value="id") / @Controller("id")
 */
@Controller  
//@Component
public class UserController {
	
	@Autowired(required=false)  // 默认情况下，required=true,代表@AutoWired标注的属性必须被装配.
	                            //可以改为required=false，有就装配，没有就算了.
	private UserService userService ;
	
	public void login(){
		System.out.println("UserController  login .....");
		userService.Handlelogin();
	}

}

package com.learn.spring.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;

import com.learn.spring.dao.UserDao;

/**
 * 业务层的组件
 *
 */
@Service
public class UserService {
	
	/**
	 *@AutoWired 优先采用类型的匹配的方式进行bean的装配. 如果有多个类型兼容的bean匹配了,会使用
	 *			 属性名 与bean的id值进行匹配. 
	 */
	@Autowired
	@Qualifier("userDaoMyBatisImpl") //进一步的指定要装配的bean的id值.
	private UserDao userDao ;
	
	public void Handlelogin(){
		System.out.println("UserService  handleLogin ....");
		//处理登录的逻辑
		userDao.getUserByUsernameAndPassword();
	}
}

package com.learn.spring.dao;

public interface UserDao {
	public void getUserByUsernameAndPassword();	
	
}

package com.learn.spring.dao;

import org.springframework.stereotype.Repository;

@Repository
public class UserDaoJdbcImpl  implements UserDao{
	
	public void getUserByUsernameAndPassword(){
		System.out.println("UserDaoJdbcImpl getUserByUsernameAndPassword......");
	}
}

package com.learn.spring.test;

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

import com.learn.spring.controller.UserController;
import com.learn.spring.dao.UserDao;
import com.learn.spring.service.UserService;

public class TestAnnotation {
	public static void main(String[] args) {
		//.1实例化ioc容器
		ApplicationContext ctx = 
				new ClassPathXmlApplicationContext("applicationContext.xml");
		//2.获取bean
		UserController  userController =(UserController) ctx.getBean("userController");
		System.out.println("userController:" + userController);
		
		userController.login();
	}
}