1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2 pageEncoding="UTF-8"%> 3 <!DOCTYPE html> 4 <html> 5 <head> 6 <meta charset="UTF-8"> 7 <title>Insert title here</title> 8 </head> 9 <body> 10 <form action="Check.jsp" method="post"> 11 姓名：<input type="text" name="uname"></br> 12 密码：<input type="password" name="upwd"></br> 13 <input type="submit" value="登录"> 14 </form> 15 </body> 16 </html>
1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2 pageEncoding="UTF-8"%> 3 <%@page import="dn.studyjavaweb.LoginDemo" %> 4 <!DOCTYPE html> 5 <html> 6 <head> 7 <meta charset="UTF-8"> 8 <title>Insert title here</title> 9 </head> 10 <body> 11 <% 12 //接收login.jsp传来的数据 13 request.setCharacterEncoding("UTF-8"); 14 String uname=request.getParameter("uname"); 15 String upwd=request.getParameter("upwd"); 16 17 //创建LoginDemo对象 18 LoginDemo log=new LoginDemo(); 19 20 //调用loginCheck函数 21 int flag=log.loginCheck(uname, upwd); 22 23 //判断登录状态 24 if(flag==0){ 25 out.print("用户名或密码错误！"); 26 }else if(flag==1){ 27 out.print("登陆成功！"); 28 }else{ 29 out.print("系统错误！"); 30 } 31 %> 32 </body> 33 </html>
1 package dn.studyjavaweb; 2 3 import java.sql.Connection; 4 import java.sql.DriverManager; 5 import java.sql.PreparedStatement; 6 import java.sql.ResultSet; 7 import java.sql.SQLException; 8 9 public class LoginDemo { 10 public int loginCheck(String uname,String upwd) { 11 final String URL="jdbc:mysql://localhost:3306/javawebpro?useSSL=false&serverTimezone=UTC"; 12 final String NAME="root"; 13 final String PWD="123456"; 14 Connection conn=null; 15 PreparedStatement pstmt=null; 16 ResultSet count=null; 17 try { 18 //加载驱动 19 Class.forName("com.mysql.cj.jdbc.Driver"); 20 //建立连接 21 conn=DriverManager.getConnection(URL, NAME, PWD); 22 //创建preparedStatement需要把SQL语句写在前面 23 String sql="select * from user where username=? and userpassword=?"; 24 //创建preparedStatement，将SQL预编译 25 pstmt=conn.prepareStatement(sql); 26 //替换占位符 27 pstmt.setString(1, uname); 28 pstmt.setString(2, upwd); 29 //执行SQL语句 30 count=pstmt.executeQuery(); 31 //结果判断 32 if(count.next()==true) { 33 return 1; 34 }else { 35 return 0; 36 } 37 } catch (ClassNotFoundException e) { 38 e.printStackTrace(); 39 return -1; 40 }catch (SQLException e) { 41 e.printStackTrace(); 42 return -1; 43 }catch (Exception e) { 44 e.printStackTrace(); 45 return -1; 46 }finally { 47 try { 48 //关闭结果、连接等，先开后关 49 if(count!=null)count.close(); 50 if(pstmt!=null)pstmt.close(); 51 if(conn!=null)conn.close(); 52 } catch (SQLException e) { 53 e.printStackTrace(); 54 }catch (Exception e) { 55 e.printStackTrace(); 56 } 57 } 58 } 59 60 }
上述是我用Eclipse代码敲的代码
下面是我遇到的问题：
1.Class.forName("com.mysql.cj.jdbc.Driver");报错
错误1：将"com.mysql.cj.jdbc.Driver"写成"com.mysql.jdbc.Driver"。我的MySQL是8.0版本的，驱动由"com.mysql.jdbc.Driver"变成了"com.mysql.cj.jdbc.Driver"。
错误2：将驱动加载错误，在Eclipse中应该将驱动粘贴到WEB-INF中的lib下
2.conn=DriverManager.getConnection(URL, NAME, PWD);报错
错误1：URL写错
错误2：NAME和PWD与uname和upwd弄混淆
3.count=pstmt.executeQuery(); 出现No value specified for parameter 1
因为有占位符，所以先set它们的值在执行SQL语句