JAVAweb实现简单的登录注册以及表格填报功能（学生初学者水平）

package com.tongji.dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import com.tongji.util.UserException; import com.tongji.util.MessageException; import com.tongji.util.DBUtil; import com.tongji.model.User; import sun.net.www.content.text.plain; public class UserDaoImpl implements IUserDao { @Override public void add(User user) { //获得链接对象 Connection connection = DBUtil.getConnection(); //准备sql语句 String sql ="select count(*) from t_user where username= ?"; //创建语句传输对象 PreparedStatement preparedStatement = null; ResultSet resultSet = null; try { preparedStatement = connection.prepareStatement(sql); preparedStatement.setString(1, user.getUsername()); //接收结果集 resultSet = preparedStatement.executeQuery(); //遍历结果集 while(resultSet.next()) { if (resultSet.getInt(1) > 0) { throw new UserException("用户已存在") ; } } sql = "insert into t_user(username,password,ptname,year,month,day,jsfiled) values (?,?,?,?,?,?,?)"; preparedStatement = connection.prepareStatement(sql); preparedStatement.setString(1, user.getUsername()); preparedStatement.setString(2, user.getPassword()); preparedStatement.setString(3, user.getPtname()); preparedStatement.setString(4, user.getYear()); preparedStatement.setString(5, user.getMonth()); preparedStatement.setString(6, user.getDay()); preparedStatement.setString(7, user.getJsfiled()); preparedStatement.executeUpdate(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally { //关闭资源 DBUtil.close(resultSet); DBUtil.close(preparedStatement); DBUtil.close(connection); } } public User login(String username, String password) { Connection connection = DBUtil.getConnection(); //String sql = "select * from t_user where username=? and password=?"; String sql = "select * from t_user where username=?"; PreparedStatement preparedStatement = null; ResultSet resultSet = null; User user = null; try { preparedStatement = connection.prepareStatement(sql); preparedStatement.setString(1, username); //preparedStatement.setString(2, password); resultSet = preparedStatement.executeQuery(); while (resultSet.next()) { user = new User(); user.setId(resultSet.getInt("id")); user.setUsername(resultSet.getString("username")); user.setPassword(resultSet.getString("password")); user.setPtname(resultSet.getString("ptname")); user.setYear(resultSet.getString("year")); user.setMonth(resultSet.getString("month")); user.setDay(resultSet.getString("day")); user.setJsfiled(resultSet.getString("jsfiled")); } if (user == null) { throw new MessageException("用户不存在!"); } if (!user.getPassword().equals(password) ) { throw new MessageException("密码错误!"); } }catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(resultSet); DBUtil.close(preparedStatement); DBUtil.close(connection); } return user; } public int id(String username, String password) { Connection connection = DBUtil.getConnection(); //String sql = "select * from t_user where username=? and password=?"; String sql = "select * from t_user where username=?"; PreparedStatement preparedStatement = null; ResultSet resultSet = null; User user = null; int id = 1; try { preparedStatement = connection.prepareStatement(sql); preparedStatement.setString(1, username); //preparedStatement.setString(2, password); resultSet = preparedStatement.executeQuery(); while (resultSet.next()) { user = new User(); user.setId(resultSet.getInt("id")); user.setUsername(resultSet.getString("username")); user.setPassword(resultSet.getString("password")); user.setPtname(resultSet.getString("ptname")); user.setYear(resultSet.getString("year")); user.setMonth(resultSet.getString("month")); user.setDay(resultSet.getString("day")); user.setJsfiled(resultSet.getString("jsfiled")); id = resultSet.getInt("id"); } if (user == null) { throw new MessageException("用户不存在!"); } if (!user.getPassword().equals(password) ) { throw new MessageException("密码错误!"); } }catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(resultSet); DBUtil.close(preparedStatement); DBUtil.close(connection); } return id; } }