Java判断UserAgent为PC javaweb登陆判断用户身份

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编程梦想家 2024-06-06 16:29:08

文章标签 Java判断UserAgent为PC servlet java web 验证码 文章分类 Java 后端开发

JavaWeb学习案例笔记

文章目录

一、简介
二、代码实现

登录页面login.jsp
验证码生成CheckCodeServlet.java
判断验证码是否正确LoginServlet.java
登录成功后跳转success.jsp

三、值得注意的地方

1、LoginServlet中注意编码
2、LoginServle中这个地方还可以用BeanUtils进行优化
3、CheckCodeServlet记得吧验证码加入到session
4、判断验证码不区分大小写
5、记得每次生成验证码后删除，不然下一次现在的验证码字符和判断的验证码字符不一致

一、简介

涉及的知识点
Cookie，session

案例需求：

访问带有验证码的登录页面login.jsp
用户输入用户名，密码以及验证码。
* 如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误
* 如果验证码输入有误，跳转登录页面，提示：验证码错误
* 如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您

实现流程

Java判断UserAgent为PC javaweb登陆判断用户身份_验证码

二、代码实现

登录页面login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>login</title>

    <script>
        window.onload = function (){
            document.getElementById("img").onclick = function (){
                this.src = "/day16_cookie_session_war_exploded/checkCodeServlet?time="+new Date().getTime();
            }
        }
    </script>

    <style>
        div{
            color: red;
        }

    </style>
</head>
<body>
    <form action="/day16_cookie_session_war_exploded/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>
            </tr>

            <tr>
                <td colspan="2"><img id="img" src="/day16_cookie_session_war_exploded/checkCodeServlet"> </td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="登录"></td>
            </tr>
        </table>
    </form>

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

</body>
</html>

验证码生成CheckCodeServlet.java

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 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);
        //设置字体大小。好像没成
        Font font = new Font("copperplate",Font.BOLD,30);
        g.setFont(font);

        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();
        //将验证码存入Session
        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);
    }
}

判断验证码是否正确LoginServlet.java

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.设置request编码
        request.setCharacterEncoding("utf-8");
        //2.获取参数。也可使用BeanUtils获取Map集合
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String checkCode = request.getParameter("checkCode");
        //3.先获取生成的验证码
        HttpSession session = request.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");
        //删除session中存储的验证码
        session.removeAttribute("checkCode_session");


        //3.先判断验证码是否正确
        if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){  //equalsIgnoreCase方法，忽略大小写的比较
            //忽略大小写比较

            //验证码正确，判断用户名和密码是否一致
            if("zhangsan".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库
                //登录成功
                //存储信息，用户信息
                session.setAttribute("user",username);
                //重定向到success.jsp
                response.sendRedirect(request.getContextPath()+"/success.jsp");
            }else{
                //登录失败
                //存储提示信息到request
                request.setAttribute("login_error","用户名或密码错误");
                //转发到登录页面
                request.getRequestDispatcher("/login.jsp").forward(request,response);
            }


        }else{
            //验证码不一致
            //存储提示信息到request
            request.setAttribute("cc_error","验证码错误");
            //转发到登录页面
            request.getRequestDispatcher("/login.jsp").forward(request,response);

        }

    }

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

登录成功后跳转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>