注解模式2(自动注入和多个实现接口的子类的用法)

1、配置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:mvc="http://www.springframework.org/schema/mvc"
	xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xmlns:c="http://www.springframework.org/schema/c"
	xmlns:cache="http://www.springframework.org/schema/cache"
	xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
		http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache-4.0.xsd
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd">
	
	<context:component-scan base-package="com.wh"></context:component-scan> 
	
</beans>

2、编写接口

package com.wh.zhujie;

import org.springframework.stereotype.Repository;

@Repository
public interface IDao {
	
	String info();

}

3、编写实现接口的不同子类

package com.wh.zhujie;

import org.springframework.stereotype.Repository;

@Repository
public class MySqlDaoImpl implements IDao {

	@Override
	public String info() {
		return "mySqlDaoImpl";
	}

}

package com.wh.zhujie;

import org.springframework.stereotype.Repository;

@Repository
public class OracleDaoImpl implements IDao {

	@Override
	public String info() {
		return "OracleDaoImpl";
	}

}

4、编写service层的类

package com.wh.zhujie;

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

/**
 * @Resource(name="mySqlDaoImpl")     手动注入
 * @Autowire                          自动注入
 * 
 * 若出现一个接口对应多个不同的子类实现时，可以通过
 * @Qualifier(value="oracleDaoImpl")
 * 来确定使用哪个子类实现
 */

@Service
public class UserService {
	@Autowired
	@Qualifier(value="oracleDaoImpl")
	private IDao dao;

	public String info() {
		return dao.info();
	}

	public IDao getDao() {
		return dao;
	}

	public void setDao(IDao dao) {
		this.dao = dao;
	}

}

5、编写测试类

package com.wh.zhujie;

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

public class TestMVC {

	public static void main(String[] args) {
		ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext.xml");
		UserService us=(UserService)ac.getBean("userService");
		System.out.println(us.info());
	}

	/**
	 * 运行结果：
	 *    OracleDaoImpl
	 */
}