Java教程

案例_验证码

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案例_验证码

案例需求：

  1. 访问带有验证码的登录页面login.jsp
  2. 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

分析

 

 java代码

验证码

package com.bai.Servlet;

import javax.imageio.ImageIO;
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 java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/CheckCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) 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);
        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="ABCDEFGHIJLMNOPQRTUVWXYZabcdefghigklmnopqstuvwxyz0123456789";

        //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
        req.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,x2,y1,y2);
        }

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



    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

登录页面

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2022/8/16
  Time: 10:54
  To change this template use File | Settings | File Templates.
--%>
<%@ 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="/CheckCodeServlet?time="+new Date().getTime();
        }
    }
</script>
    <style>
        div{
            color:red;
        }
    </style>

</head>
<body>
    <form action="/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="/CheckCodeServlet"></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" name="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>

业务层

package com.bai.Servlet;

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 {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置request编码
        req.setCharacterEncoding("utf-8");
        //获取参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String checkCode = req.getParameter("checkCode");
        //获取生成的验证码
        HttpSession session = req.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");
        //判断验证码是否正确
        if (checkCode_session.equals(checkCode)) {
            //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
                resp.sendRedirect(req.getContextPath() + "/success.jsp");
            } else {
                //登录失败
                //存储提示信息到request
                req.setAttribute("login_error", "用户名或密码错误");
                //转发到登录页面
                req.getRequestDispatcher("/login.jsp").forward(req, resp);
            }

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


    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

登录成功页面

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2022/8/16
  Time: 11:52
  To change this template use File | Settings | File Templates.
--%>
<%@ 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>

运行结果

登录页面

 

 验证码输入错误

 

 用户名和密码输入错误

 

登录成功

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