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最近项目中需要对mysql进行操作，数据库的知识早在本科毕业那会就忘光了，这几年开发都没接触到数据库的操作。
借这个机会重新学习，数据库访问层是对数据库操作的一个封装，屏蔽底层的数据操作细节，通过使用DAO对数据库进行增删改查操作。
本文将以项目中的一小部分为例，介绍如何编写数据库访问层：
1. 实体类对象
1 public class CheckInfo { 2 private Integer id; 3 private String userName; 4 private Timestamp checkTime; 5 6 public Integer getId() { 7 return id; 8 } 9 10 public void setId(Integer id) { 11 this.id = id; 12 } 13 14 public String getUserName() { 15 return userName; 16 } 17 18 public void setUserName(String userName) { 19 this.userName = userName; 20 } 21 22 public Timestamp getCheckTime() { 23 return checkTime; 24 } 25 26 public void setCheckTime(Timestamp checkTime) { 27 this.checkTime = checkTime; 28 } 29 30 @Override 31 public String toString() { 32 return "CheckInfo [id=" + id + ", userName=" + userName 33 + ", checkTime=" + checkTime + "]"; 34 } 35 36 }
2. 获取数据库连接工具类ConnectionUtil
1 public class ConnectionUtil { 2 3 public Connection getConnection() { 4 String username = "root"; 5 String password = "123456"; 6 String url="jdbc:mysql://localhost:3306/checkin"; 7 String driver="com.mysql.jdbc.Driver"; 8 9 try { 10 Class.forName(driver); 11 return DriverManager.getConnection(url, username, password); 12 } catch (ClassNotFoundException e) { 13 e.printStackTrace(); 14 } catch (SQLException e) { 15 e.printStackTrace(); 16 } 17 return null; 18 } 19 }
3. 数据访问层接口
1 public interface CheckInfoDAO { 2 3 public boolean save(CheckInfo checkInfo); 4 public List<CheckInfo> listCheckInfo(); 5 6 }
4. 数据访问层实现
1 public class CheckInfoDAOImpl implements CheckInfoDAO { 2 3 @Override 4 public boolean save(CheckInfo checkInfo) { 5 boolean flag = false; 6 ConnectionUtil connUtil = new ConnectionUtil(); 7 Connection conn = null; 8 9 conn = connUtil.getConnection(); 10 11 PreparedStatement stmt = null; 12 String sql = "insert into checkinfo values(name, time) values(" 13 + checkInfo.getUserName() + "," + checkInfo.getCheckTime() 14 + ")"; 15 try { 16 stmt = conn.prepareStatement(sql); 17 flag = stmt.execute(); 18 } catch (SQLException e) { 19 e.printStackTrace(); 20 } 21 22 return flag; 23 } 24 25 @Override 26 public List<CheckInfo> listCheckInfo() { 27 List<CheckInfo> checkInfos = new ArrayList<CheckInfo>(); 28 29 ConnectionUtil connUtil = new ConnectionUtil(); 30 Connection conn = null; 31 32 conn = connUtil.getConnection(); 33 34 PreparedStatement stmt = null; 35 String sql = "select * from checkinfo"; 36 ResultSet resultSet = null; 37 38 try { 39 stmt = conn.prepareStatement(sql); 40 resultSet = stmt.executeQuery(); 41 while(resultSet.next()) { 42 CheckInfo ci = new CheckInfo(); 43 ci.setId(resultSet.getInt(1)); 44 ci.setUserName(resultSet.getString(2)); 45 ci.setCheckTime(resultSet.getTimestamp(3)); 46 checkInfos.add(ci); 47 } 48 } catch (SQLException e) { 49 e.printStackTrace(); 50 } 51 52 return checkInfos; 53 } 54 55 }
mysql中的datetime类型对应于java的TimeStamp类型。
5.测试类
1 public class TestCase { 2 3 public static void main(String[] args) { 4 5 testListCheckInfo(); 6 } 7 8 private static void testListCheckInfo() { 9 CheckInfoDAO checkInfoDAO = new CheckInfoDAOImpl(); 10 List<CheckInfo> checkInfos = checkInfoDAO.listCheckInfo(); 11 12 for (CheckInfo checkInfo : checkInfos) { 13 System.out.println(checkInfo); 14 } 15 } 16 17 }
数据库建表语句：
1 create table if not exists checkinfo ( 2 id int(10) not null primary key auto_increment, 3 userid varchar(40), 4 time datetime 5 );
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原文地址：http://www.cnblogs.com/feiling/p/4385248.html
