Spring 依赖注入 构造方法注入

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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd ">
	<bean id="Oracle" class="com.zyl.dao.UserOraDAO" />
	<bean id="Sql" class="com.zyl.dao.UserSqlDAO" />
	<bean id="User" class="com.zyl.manager.UserMessageImpl">
		<!--	<constructor-arg ref="Oracle"/>-->
		<property name="userDao" ref="Oracle" />
	</bean>
</beans>

----------------------------------------------

package com.zyl.Test;



import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.zyl.dao.UserSqlDAO;
import com.zyl.dao.UserOraDAO;
import com.zyl.manager.UserMessage;
import com.zyl.manager.UserMessageImpl;

public class TestMain {

	public static void main(String[] args) {

		/*UserMessage user = new UserMessageImpl(new UserSqlDAO());
		user.save("zyl", "123");*/
		BeanFactory factory= new ClassPathXmlApplicationContext("applicationContext.xml");
		UserMessage user =(UserMessage)factory.getBean("User");
		user.save("zyl","123");
	}
}
----------------------------------

package com.zyl.manager;

public interface UserMessage {
	public void save(String username, String password); 
}
-----------------

package com.zyl.manager;

import com.zyl.dao.UserDAO;
import com.zyl.dao.UserSqlDAO;

public class UserMessageImpl implements UserMessage {
	private UserDAO userDao;
/*	public UserMessageImpl(UserDAO userDao) {
		this.userDao=userDao;
	}*/
	public void save(String username, String password) {
		this.userDao.show(username,password);
	}
	public void setUserDao(UserDAO userDao){
		this.userDao=userDao;
		
	}
}
---------------------------------------
package com.zyl.dao;

public interface UserDAO {
	public void show(String username, String password);
}
----------------
package com.zyl.dao;

public class UserOraDAO implements UserDAO {

	public void show(String username, String password) {
		System.out.println("Oracle"+username+password);
	}

}
----------------
package com.zyl.dao;

public class UserSqlDAO implements UserDAO {

	public void show(String username, String password) {
		System.out.println("Sql"+username+password);
	}

}
------------------------------------