JDBC+MySQL 之 DAO模式

约定不等于承诺〃 2021-06-24 16:10 423阅读 0赞

# DAO模式 #

> Data Access Object 数据访问对象

## 工程目录结构： ##

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## 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");
        	}
        }

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