JavaWeb实现简单的带有验证码的用户判断登录案例

叁歲伎倆 2023-09-23 15:07 81阅读 0赞

> 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：**

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

**实现流程**  
![在这里插入图片描述][d2f8bbb9df104651b57ea42a8cfb8697.png]

# 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>

# 三、值得注意的地方 #

## 1、LoginServlet中注意编码 ##

![在这里插入图片描述][1dc8c1010a9449deb10ef9447ff2b21b.png]

## 2、LoginServle中这个地方还可以用BeanUtils进行优化 ##

![在这里插入图片描述][446dce09f1134c40afd4852ae7c6e14c.png]

## 3、CheckCodeServlet记得吧验证码加入到session ##

![在这里插入图片描述][29e6bf1717d9455caebf1c931fbfc126.png]

## 4、判断验证码不区分大小写 ##

LoginServlet中  
![在这里插入图片描述][ece063b38dec410caceb9e620c8c5c51.png]

## 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 ##

LoginServlet中  
![在这里插入图片描述][7a0c432997c8443783e15b4bf144c1db.png]

来源：B站黑马程序员JavaWeb网课

[d2f8bbb9df104651b57ea42a8cfb8697.png]: https://img-blog.csdnimg.cn/d2f8bbb9df104651b57ea42a8cfb8697.png
[1dc8c1010a9449deb10ef9447ff2b21b.png]: https://img-blog.csdnimg.cn/1dc8c1010a9449deb10ef9447ff2b21b.png
[446dce09f1134c40afd4852ae7c6e14c.png]: https://img-blog.csdnimg.cn/446dce09f1134c40afd4852ae7c6e14c.png
[29e6bf1717d9455caebf1c931fbfc126.png]: https://img-blog.csdnimg.cn/29e6bf1717d9455caebf1c931fbfc126.png
[ece063b38dec410caceb9e620c8c5c51.png]: https://img-blog.csdnimg.cn/ece063b38dec410caceb9e620c8c5c51.png
[7a0c432997c8443783e15b4bf144c1db.png]: https://img-blog.csdnimg.cn/7a0c432997c8443783e15b4bf144c1db.png