java web实现用户登录注册.rar

package com.ljb.dao; import com.ljb.model.User;;import java.sql.*; public class UserSelectdao { public User selectUserByName(String username){ User user=null; try { Class.forName("com.mysql.jdbc.Driver"); } catch (ClassNotFoundException e) { e.printStackTrace(); } Connection conn=null; PreparedStatement ps=null; ResultSet rs=null;//结果集合对象，用于封装数据库查询结果 String sql=""; try { conn= DriverManager.getConnection("jdbc:mysql://localhost:3306/login","root","password"); sql="select * from user where username=?"; ps=conn.prepareStatement(sql); ps.setString(1,username); rs=ps.executeQuery();//执行数据库的查询语句并返回查询结果 while(rs.next()) {//让光标向下移动一次并判断下一个元素是否有值，有值则返回真 user =new User(); user.setUsername(rs.getString("username")); user.setPassword(rs.getString("password")); } } catch (SQLException throwables) { throwables.printStackTrace(); } finally { if(rs!=null){ try { rs.close(); } catch (SQLException throwables) { throwables.printStackTrace(); } } if(ps!=null){ try{ ps.close(); }catch(SQLException e){ e.printStackTrace(); } } if(conn!=null){ try{ conn.close(); }catch(SQLException e){ e.printStackTrace(); } } } return user; } }