DAO模式

Data Access Object 数据访问对象

工程目录结构：

实现步骤：

1. 新建一个dao的接口，里面声明数据库访问规则。

   package com.veeja.dao;
   
   /**
    * 定义操作数据库的方法
    * @author veeja
    */
   public interface UserDao {
   
   	/**
   	 * 查询所有
   	 */
   	void findAll();
   
   	/**
   	 * 登录方法
   	 * @param username
   	 * @param password
   	 */
   	void login(String username,String password);
   	
   }
   

2. 新建一个dao的实现类，具体实现早前定义的规则。

   public class UserDaoImpl implements UserDao {
   
   	@Override
   	public void findAll() {
   
   		Connection conn = null;
   		Statement st = null;
   		ResultSet rs = null;
   
   		try {
   			// 获取连接对象
   			conn = JDBCUtil.getConn();
   
   			// 创建statement对象
   			st = conn.createStatement();
   						
   			// 执行SQL语句，得到结果集			
   			String sql = "select * from t_user";
   			rs = st.executeQuery(sql);
   			
   			// 遍历结果集
   			while(rs.next())
   			{
   				String username = rs.getString("username");
   				String password = rs.getString("password");
   				System.out.println("username = "+username+"\tpassword = "+password);
   			}	
   		} catch (Exception e) {
   			e.printStackTrace();
   		} finally {
   			JDBCUtil.release(conn, st, rs);
   		}
   	}
   	
   	@Override
   	public void login(String username, String password) {
   		// TODO Auto-generated method stub
   		Connection conn = null;
   		Statement st = null;
   		ResultSet rs = null;
   
   		try {
   			conn = JDBCUtil.getConn();
   			st = conn.createStatement();
   
   			String sql = "select * from t_user where username='" + username + "' and password = '" + password + "'";
   			rs = st.executeQuery(sql);
   
   			if (rs.next()) {
   				System.out.println("登录成功！");
   			} else {
   				System.out.println("登陆失败！");
   			}
   
   		} catch (Exception e) {
   			e.printStackTrace();
   		} finally {
   			JDBCUtil.release(conn, st, rs);
   		}
   	}	
   }
   

3. 直接使用实现。

   public class TestUserDaoImpl {
   
   	@Test
   	public void testFindAll() {
   		UserDao dao = new UserDaoImpl();
   		dao.findAll();
   	}
   
   	@Test
   	public void testLogin() {
   		UserDao dao = new UserDaoImpl();
   		dao.login("zhangsan","10010");
   	}
   }