怎样验证jsp页面输入的用户名与密码和数据库中的一致？

Posted 2023-03-31

参考技术A 将jsp中获取到的用户名和密码传递到后台,然后后台在从数据库中查询出改用户名所对应的密码,如果相同就表示是正确的.或者将用户名和密码同时放入数据库进行查询,如果查询的到数据说明是对的.后一种以前常备用来进行注入攻击.追问

代码怎么写啊？

追答

代码就多了去了,而且实现方式也有很多.真还不是一句两句就弄得清楚地.

追问

大神，文件图片上传的servlet怎么写啊？可以上传就是上传的结果没出现，求帮忙

追答

可以使用fileupload组件来上传.

Session+JSP Demo

验证码案例: 

需求:
 1.访问带有验证码的登录页面login.js
 2.用户输入用户名和密码

• 如果用户名和密码错误,跳转到登录页面,提示用户名密码错误
• 如果验证码有误,跳转到登录页面,提示验证码错误
• 如果全部输入正确,则跳转到success.jsp,显示用户名,欢迎您!

步骤:
 1.设置request的编码
 2.获取参数Map集合
 3.获取验证码
 4.将用户信息封装到User对象
 5.判断程序生成的验证码和用户输入的验证码是否一致,从session中获取程序生成的验证码
      *一致
          在此判断用户名和密码是否一致(查询数据库)
             正确:登录成功,存储数据,跳转到页面(重定向Session域)
             不正确:给提示信息,跳转登录页面

     *不一致
          1.给用户提示信息,验证码错误 request
          2.跳转登录页面 转发

LoginServlet

package com.infosys.session;

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 javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 

        request.setCharacterEncoding("utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String checkCode = request.getParameter("checkCode");

        HttpSession session = request.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");

        if (checkCode_session.equalsIgnoreCase(checkCode)) 
            if ("zhangsan".equals(username) && "123".equals(password)) 
                session.setAttribute("user", username);
                response.sendRedirect(request.getContextPath() + "/success.jsp");
             else 
                request.setAttribute("login_error", "用户名或密码错误");
                request.getRequestDispatcher("/login.jsp").forward(request, response);
            

         else 
            request.setAttribute("cc_error", "验证码错误");
            request.getRequestDispatcher("/login.jsp").forward(request, response);
        


    

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
        this.doPost(request, response);
    

 

CheckCodeServlet 

package com.infosys.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet 
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 


        int width = 100;
        int height = 50;

        //1.创建一对象，在内存中图片(验证码图片对象)
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);


        //2.美化图片
        //2.1 填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.PINK);//设置画笔颜色
        g.fillRect(0, 0, width, height);

        //2.2画边框
        g.setColor(Color.BLUE);
        g.drawRect(0, 0, width - 1, height - 1);

        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random ran = new Random();
        StringBuilder sb = new StringBuilder();

        for (int i = 1; i <= 4; i++) 
            int index = ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);//随机字符
            sb.append(ch);
            //2.3写验证码
            g.drawString(ch + "", width / 5 * i, height / 2);
        
        String checkCode_session = sb.toString();

        request.getSession().setAttribute("checkCode_session", checkCode_session);
        //2.4画干扰线
        g.setColor(Color.GREEN);

        //随机生成坐标点

        for (int i = 0; i < 10; i++) 
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);

            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            g.drawLine(x1, y1, x2, y2);
        


        //3.将图片输出到页面展示
        ImageIO.write(image, "jpg", response.getOutputStream());


    

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
        this.doPost(request, response);
    

 

login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
    <script>
        window.onload = function () 
            document.getElementById("img").onclick = function () 
                this.src = "/cookie/checkCodeServlet?time=" + new Date().getTime();
            
        
    </script>
</head>

<body>
<form action="/cookie/LoginServlet" method="post">
    <table>
        <tr>
            <td>用户名</td>
            <td><input type="text" name="username"/></td>
        </tr>
        <tr>
            <td>密码</td>
            <td><input type="password" name="password"/></td>
        </tr>
        <tr>
            <td>验证码</td>
            <td><input type="text" name="checkCode"/></td>

            <td colspan="2"><img src="/cookie/checkCodeServlet" id="img"/></td>
        </tr>
        <tr>
            <td colspan="2"><input type="submit" value="登录"/></td>
        </tr>
    </table>
</form>


<div><%= request.getAttribute("cc_error")%>
</div>
<div><%= request.getAttribute("login_error")%>
</div>

</body>
</html>

success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1><%=request.getSession().getAttribute("user")%>,欢迎您</h1>
</body>
</html>

 

真实数据查询数据库