Java 之 Session 包含验证码登录案例

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：

代码实现：

　　login.jsp 页面

 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 <html lang="en">
 <head>
     <meta charset="UTF-8">
     <title>登录</title>
     <script>

         window.onloa = function() {
             // 刷新验证码
             document.getElementById("img").onclick = function() {
                 this.src = "/day13/checkcodeservletdemo"+new Date().getTime();
             }
         }
     </script>
     <style>

         div {
             color:red;
         }
     </style>

 <body>
     <form action="/day13/loginservletdemo" 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="/day13/checkcodeservletdemo"></td>
             </tr>

             <tr>
                 <td colspan="2"><input type="submit" value="登录"></td>
             </tr>
         </table>

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

     </form>
 </body>
 </html>

　　success 页面

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

 </body>
 </html>

　　生成验证码 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("/checkcodeservletdemo")
 public class CheckCodeServlet extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         // 定义图片的宽高
         int width = 100;
         int height = 50;

         // 1 创建对象，在内存中生成图片（验证码图片对象）
         BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);

         // 2 修饰图片
         // 2.1 填充背景色
         Graphics g = image.getGraphics(); //获取画笔对象
         g.setColor(Color.pink);  // 设置画笔颜色
         g.fillRect(0,0,width,height);  // 绘制一个矩形，给定坐标与宽高

         // 2.2 画边框
         g.setColor(Color.blue);    // 设置画笔颜色
         g.drawRect(0,0,width-1,height-1);  // 给图像绘制边框

         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 < 6; 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);  // 画干扰线
         }

         // 3 将图片输出到页面展示：通过response 的 字符流，将图片输出到浏览器上
         ImageIO.write(image,"jpg",response.getOutputStream());
     }

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

　　登录 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("/loginservletdemo")
 public class LoginServlet extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         // 1. 设置编码
         request.setCharacterEncoding("utf-8");
         // 2. 获取参数
         //Map<String, String[]> map = request.getParameterMap();

         String username = request.getParameter("username");
         String password = request.getParameter("password");
         String checkcode = request.getParameter("checkcode");

         // 3.先判断验证码是否正确
         // 获取生成验证码
         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");

         // 判断,忽略大小写
         if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkcode)) {
             //验证码正确
             // 判断用户名和密码是否一致
             if("zhangsan".equals(username) && "123".equals(password)) {
                 // 登录成功
                 // 存储用户信息

                 session.setAttribute("user",username);
                 // 重定向到 success.jsp
                 response.sendRedirect(request.getContextPath()+"/success.jsp");
             }else {
                 // 存储提示信息到request
                 request.setAttribute("login_error","用户名或密码错误");
                 request.getRequestDispatcher("/login.jsp").forward(request,response);
             }

         } else {
             // 验证码不正确
             // 存储提示信息到request
             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);
     }
 }