javaWeb使用验证码实现简单登录

2019-11-26 08:42:50

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本文实例为大家分享了javaWeb使用验证码实现简单登录的具体代码，供大家参考，具体内容如下

简单的流程图

1.用户给第一次访问login.jsp页面时，会想服务器发送两个请求，一个请求是显示图片，还有一个是显示表单

2.第一个请求发送后服务器中verifyServlet处理，随机生成验证码图片，并保存到session中，然后响应给客户端

3.第二个请求后服务器LoginServlet处理，获取表单验证码，以及session中的验证码，再判断两个验证码是否相等，相等就向下执行即 success.jsp，否则跳转到login.jsp页面

1.创建login.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <base href="<%=basePath%>" rel="external nofollow" >  <title>My JSP 'login.jsp' starting page</title>  <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0">  <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" > -->  </head>  <body> <%--本页面提供登录表单,还有显示错误信息 --%> <h1>登录</h1>  <% //读取uname的cookie String uname=""; Cookie[] cs=request.getCookies(); if(cs!=null){  for(Cookie c:cs){  if("uname".equals(c.getName())){  uname=c.getValue();  }  } } %>  <% String message=""; String msg=(String)request.getAttribute("msg"); if(msg!=null){  message=msg;  } %>  <font color="red"><b><%=message %></b></font> <form action="/ServletDemo2/LoginServlet1" method="post">  用户名：<input type="text" name="username" value=<%=uname %> /><br>  密 码：<input type="password" name="pawword" /><br>  验证码:<input type="text" name="verifycode" size="3">  <img src="/ServletDemo2/VerifyServlet" >  <!-- <a href="javascript:_change()" rel="external nofollow" >换一张</a> -->   <input type="submit" value="登录" />  </form> </body></html>

2.success.jsp(只是简单的展示)

<body> <h1>succ1</h1> <% String username=(String)session.getAttribute("username"); if(username==null){  /*  向request域中保存错误信息，转发到login.jsp  */  request.setAttribute("msg", "请先登录再访问");  request.getRequestDispatcher("/session2/login.jsp").forward(request, response);  return; }  %>  欢迎登陆成功<%=username %> </body>

3.然后是VerifyServlet

 package com.klay.servlet.session; import java.awt.image.BufferedImage;import java.io.IOException; 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 com.klay.image.VerifyCode; /** * Servlet implementation class VerifyServlet */@WebServlet("/VerifyServlet")public class VerfiyServlet extends HttpServlet{ private static final long serialVersionUID = 1L;  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {  VerifyCode vc = new VerifyCode();  BufferedImage image = vc.getImage();  request.getSession().setAttribute("session_vcode", vc.getText());// 保存图片上的文本到session   VerifyCode.output(image, response.getOutputStream()); } }

4.LoginServlet

package com.klay.servlet.session; import java.io.IOException; import javax.servlet.RequestDispatcher;import javax.servlet.ServletException;import javax.servlet.http.Cookie;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession; public class LoginServlet extends HttpServlet{  /**  * @Fields serialVersionUID : TODO(用一句话描述这个变量表示什么)  */ private static final long serialVersionUID = 1L;  @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp)   throws ServletException, IOException {  /**   * 获取校验码   */  String sessionCode = (String) req.getSession()    .getAttribute("session_vcode");   String paraCode = req.getParameter("verifycode");   if (!paraCode.equalsIgnoreCase(sessionCode))  {   req.setAttribute("msg", "验证码错误");   req.getRequestDispatcher("/session2/login.jsp").forward(req, resp);   // return是这里执行完，就不玩下执行了。   return;  }   /**   * 获取表单信息   */  req.setCharacterEncoding("utf-8");   String username = req.getParameter("username");  String password = req.getParameter("password");   /**   * 校验用户名和密码   */  if (!"kevin".equalsIgnoreCase(username))// 成功  {   Cookie cookie = new Cookie("uname", username);   resp.addCookie(cookie);    /*    * 成功就保存用户信息到session，并重定向succ1.jsp    */   HttpSession session = req.getSession();   session.setAttribute("username", username);   resp.sendRedirect("/ServletDemo2/session2/succ1.jsp");  }  else  {// 失败   // 如果失败，保存错误信息到requset，转发到login.jsp   // (服务器内部跳转只有一个request请求，重定向会有新的request，就不能获取错误信息)   req.setAttribute("msg", "用户名或密码错误");   RequestDispatcher rd = req     .getRequestDispatcher("/session2/login.jsp");   rd.forward(req, resp);// 转发   }  } }

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。

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