servlet登录验证并返回错误信息

た入场券 2022-05-26 05:38 187阅读 0赞

index.jsp(登录界面)

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
    <%
    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">
    	
    	<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="reset" value="取消"></td>
    					</tr>
    				</table>
    		</form>
    	</div>
      </body>
    </html>

loginServlet(登录验证)

package com.dwx.servlet;
    import java.io.IOException;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import com.dwx.bean.user;
    import com.dwx.bean.userDao;
    
    /**
     * 用户登录验证
     */
    @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 username=request.getParameter("username");
    		String password=request.getParameter("password");
    		//判断用户名、密码是否为空
    		if(username==""||username.length()==0){
    			request.setAttribute("namemsg","用户名为空!");
    			request.getRequestDispatcher("index.jsp").forward(request, response);
    		}
    		if(password==""||password.length()==0){
    			request.setAttribute("pwdmsg","密码为空!");
    			request.getRequestDispatcher("index.jsp").forward(request, response);
    		}
    		//判断用户名、密码是否正确
    		ResultSet rst=userDao.selectUser(username, password);
    		try {
    			if(rst.next()){
    				if(password.equals(rst.getString("password"))){
    					request.setAttribute("username",username);
    					request.getRequestDispatcher("items.jsp").forward(request, response);
    				}else{
    					request.setAttribute("pwdError","密码不正确!");
    					request.getRequestDispatcher("index.jsp").forward(request, response);
    				}
    			}else{
    				request.setAttribute("nameError","用户名不存在!");
    				request.getRequestDispatcher("index.jsp").forward(request, response);
    			}
    		} catch (SQLException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}
    
    }

userDao.java(查询用户)

package com.dwx.bean;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.util.ArrayList;
    import java.util.List;
    import com.dwx.util.dao;
    public class userDao {
    	public static ResultSet selectUser(String username,String password){
    		Connection conn=dao.getConnection();
    		String sql="select * from user where username=?";
    		ResultSet rst=null;
    		try{
    			PreparedStatement prst=conn.prepareStatement(sql);
    			prst.setString(1, username);
    			rst=prst.executeQuery();
    		}catch(Exception ex){
    			ex.printStackTrace();
    		}
    		return rst;
    	}
    }

dao.java(建立数据库连接)

package com.dwx.util;
    import java.sql.Connection;
    import java.sql.DriverManager;
    public class dao {
    	public static Connection getConnection(){
    		Connection conn=null;
    		try{
    			Class.forName("com.mysql.jdbc.Driver");		//加载驱动
    			String url="jdbc:mysql://localhost:3306/db_item";
    			String username="root";
    			String password="root";
    			//创建数据库连接
    			conn=DriverManager.getConnection(url,username,password);
    		}catch(Exception ex){
    			ex.printStackTrace();
    		}
    		return conn;
    	}
    }

效果演示：

1、用户名为空

![20180426091106512][]

2、密码为空

![20180426091144577][]

3、用户名不存在

![2018042609115784][]

4、密码不正确

![20180426091125144][]

5、登录成功

![20180426091359158][]

[20180426091106512]: /images/20220526/30eb7b81faa848dca69c3023d93c6dad.png
[20180426091144577]: /images/20220526/ec335a041c114142b093a58b4ed730b6.png
[2018042609115784]: /images/20220526/fd82be9c576b4130ba13f881f42d3bcc.png
[20180426091125144]: /images/20220526/3d3c6fd403c941e88b0d5a5e1112b312.png
[20180426091359158]: /images/20220526/7dfa78829540491ea4d316f82067000f.png