实现整体代码(需要自提，记得点赞)
Servlet代码（loginServlet.java）
package servlet;
import java.io.IOException;
import java.sql.*;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* @author s
* @version 1.0
*/
@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public loginServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String s1=request.getParameter("username");
String s2=request.getParameter("password");
request.setAttribute("s1", s1);
//判断用户名、密码是否为空
if(s1 == "" || s1.length() == 0){
request.setAttribute("namemsg","用户名为空!");
request.getRequestDispatcher("index.jsp").forward(request, response);
}
if(s2== "" || s2.length() == 0){
request.setAttribute("pwdmsg","密码为空!");
request.getRequestDispatcher("index.jsp").forward(request, response);
}
//密码部分结束
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html");
response.setCharacterEncoding("UTF-8");
//加载mysql驱动
String url ="jdbc:mysql://localhost:3306/abc";
String user = "root";
String password = "123456";
try {
Class.forName("com.mysql.jdbc.Driver");
// 连接数据库
Connection connection = DriverManager.getConnection(url,user,password);
Statement statement = connection.createStatement();
String sql = String.format("SELECT * FROM login WHERE `username` = '%s' AND `password` = '%s'",s1,s2);
ResultSet resultSet = statement.executeQuery(sql);//返回的结果集
if (resultSet.next()){
request.getRequestDispatcher("login.jsp").forward(request,response);
}else if(s1.equals("") || s2.equals("")){
request.getRequestDispatcher("loginf.jsp").forward(request,response);
}
else{request.getRequestDispatcher("loginf.jsp").forward(request,response);}
}catch(ClassNotFoundException | SQLException e) {
e.printStackTrace();
System.out.println("失败");
}
}
}
jsp代码(index.jsp)
<%--
Created by IntelliJ IDEA.
User: 86151
Date: 2022/5/24
Time: 14:32
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>用户登录</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<style type="text/css">
</style>
</head>
<body>
<div>
<form action="loginServlet" method="post">
<table align="center" >
<tr>
<td>用户名:</td>
<td><input type="text" name="username"> <font color="red">
${requestScope.namemsg}${requestScope.nameError}</font></td>
</tr>
<tr>
<td>密码:</td>
<td><input type="password" name="password"> <font color="red">
${requestScope.pwdError}${requestScope.pwdmsg}</font></td>
</tr>
<tr>
<td></td>
<td><input type="submit" value="登录">
<input type="button" value="注册" onclick='location.href=("registered.jsp")' />
</td>
</tr>
</table>
</form>
</div>
<%--<p align="center">--%>
<%--<a href="goods_bean_index.jsp">管理员登录</a>--%>
<%--</p>--%>
</body>
</html>
实现效果
登录页面
账号 or 密码 为null
两个账户分别登录成功
登录失败
