javaWeb使用验证码实现简单登录

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+"/";
%>
 


 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 <%--本页面提供登录表单,还有显示错误信息 --%>
 登录 
 <%
 //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;
 }
 %>
 
 <%=message %>
 
 

2.success.jsp(只是简单的展示)

 succ1
 <%
 String username=(String)session.getAttribute("username");
 if(username==null){
 
 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 %>
 

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;
 

@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
{
 
 
 private static final long serialVersionUID = 1L;
 
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp)
  throws ServletException, IOException
 {
 
 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;
 }
 
 
 req.setCharacterEncoding("utf-8");
 
 String username = req.getParameter("username");
 String password = req.getParameter("password");
 
 
 if (!"kevin".equalsIgnoreCase(username))// 成功
 {
  cookie cookie = new cookie("uname", username);
  resp.addcookie(cookie);
 
  
  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
 
 }
 
 }
 
}

更多关于验证码的文章请点击查看： 《java验证码》

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考高分网。