MyJDBC_qiu

package com.qiuchanghong.myjdbc.ch1; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; public class Userqjdbc implements Userq { public void delUser(String username) { //定义链接对象 Connection connection=null; PreparedStatement statement=null; //定义SQL语句 String sql="delete fron user where username=?"; try { //获得链接 connection=MySQLConnect.getIntence(); //获得SQL语句对象 statement=connection.prepareStatement(sql); //填充SQL对象参数 statement.setString(1, username); //删除指定的记录 statement.executeUpdate(); //提交记录 connection.commit(); } catch(SQLException a) { a.printStackTrace(); } finally { try { if(connection!=null) connection.close(); if(statement!=null) statement.close(); } catch(SQLException b) { System.out.println("关闭数据库出错，请与系统管理员联系！"); b.printStackTrace(); } } } public int insertUser(User user) { //定义返回值 int value=-1; //定义连接对象 Connection connection=null; PreparedStatement statement=null; //定义sql语句 String sql="insert user(username ,password,falg)values (?,?,?)"; try { //获得连接对象 connection=MySQLConnect.getIntence(); //获得SQL语句对象 statement=connection.prepareStatement(sql); //填充SQL对象参数 statement.setString(1, user.getUsername()); statement.setString(2, user.getPassword()); statement.setString(3, user.getFlag()); // 往User表中添加一条记录 value = statement.executeUpdate(); // 提交 connection.commit(); // 返回结果 return value; } catch(SQLException e) { e.printStackTrace(); } finally { try { if(statement != null) statement.close(); if(connection != null) connection.close(); } catch(SQLException e) { System.out.println("关闭数据库出错，请与系统管理员联系！"); e.printStackTrace(); } } return value; } public int updateUser(User user) { //定义一个返回值 int value=-1; //定义一个连接对象 Connection connection=null; PreparedStatement statement=null; //定义一个查寻语句 String sql="update user set username=?,password=?,flag=?"; try { //获得链接对象 connection=MySQLConnect.getIntence(); //获得SQL语句对象 statement=connection.prepareStatement(sql); //填充SQL对象参数 statement.setString(1, user.getUsername()); statement.setString(2, user.getPassword()); statement.setString(3, user.getFlag()); //修改表中制定的值 value=statement.executeUpdate(); //提交 connection.commit(); return value; } catch(SQLException e) { e.printStackTrace(); } finally { try { if(statement!=null) statement.close(); if(connection!=null) connection.close(); } catch(SQLException f) { System.out.println("关闭数据库出错，请与系统管理员联系！"); f.printStackTrace(); } } return value; } public List<User> getAllUsers() { // 定义返回值 List<User> users = new ArrayList<User>(); String sql = "select * from user"; // 定义连接对象 Connection connection = null; PreparedStatement statement = null; ResultSet resultSet = null; try { connection = MySQLConnect.getIntence(); statement = connection.prepareStatement(sql); // 获得查询结果 resultSet = statement.executeQuery(); // 处理结果集 while(resultSet.next()) { // 定义User对象 User user = new User(); // 用查询出来的记录填充User对象 user.setUsername(resultSet.getString("username")); user.setPassword(resultSet.getString("password")); user.setFlag(resultSet.getString("flag")); // 将User对象放入集合中 users.add(user); } return users; } catch(SQLException e) { e.printStackTrace(); } finally { try { if(resultSet != null) resultSet.close(); if(statement != null) statement.close(); if(connection != null) connection.close(); } catch(SQLException e) { System.out.println("关闭数据库出错，请与系统管理员联系！"); e.printStackTrace(); } } return users; } }