科技优家 2017-06-12 12:10
昨天在网上看到了一篇关于验证码的文章，很不错，但是有些不尽人意的地方，比如没有考虑到前端传过来的验证码如果是小写的话，那么做验证的时候就会出现错误，
因为java是严格区分大小写的，还有就是验证码会重叠在一起的情况没有考虑到，再者验证码看不清刷新的功能没有做出来
在此我做下修改：
首先需要导入ValidateCode.jar包
1 package com.wqy.ValidateCode; 2 3 import java.io.IOException; 4 5 import javax.imageio.ImageIO; 6 import javax.servlet.ServletException; 7 import javax.servlet.http.HttpServlet; 8 import javax.servlet.http.HttpServletRequest; 9 import javax.servlet.http.HttpServletResponse; 10 11 import cn.dsna.util.images.ValidateCode; 12 13 public class ValidateCode1 extends HttpServlet { 14 15 public void doGet(HttpServletRequest request, HttpServletResponse response) 16 throws ServletException, IOException { 17 //控制不要缓存 18 response.setHeader("Expires", "-1"); 19 response.setHeader("Cache-Control", "no-cache"); 20 response.setHeader("Pragma", "no-cache"); 21 int width=120;//宽度 22 int height=25;//高度 23 int codeCount=4;//验证码的个数 24 int lineCount=9;//干扰线的个数 25 //设置验证码 26 ValidateCode vc = new ValidateCode(width, height, codeCount, lineCount); 27 //ValidateCode(120,25,4,9); 28 String code = vc.getCode; 29 //将验证码存放到Attribute域中 30 request.getSession.setAttribute("code", code); 31 //输出 32 ImageIO.write(vc.getBuffImg, "jpg", response.getOutputStream); 33 34 } 35 36 public void doPost(HttpServletRequest request, HttpServletResponse response) 37 throws ServletException, IOException { 38 doGet(request,response); 39 } 40 41 }
下面是html代码：
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%> <% String path = request.getContextPath; String basePath = request.getScheme+"://"+request.getServerName+":"+request.getServerPort+path+"/"; %> <html> <head> <title>验证码</title> </head> <body> <form action="${pageContext.request.contextPath}/servlet/LoginServlet" method="post"> 用户名:<input type="text" name="username"/></br> 密码:<input type="password" name="password"/></br> 验证码:<input type="text" name="captcha" size="4"> <img src="${pageContext.request.contextPath}/servlet/ValidateCode1" id="CreateCheckCode" onclick="this.src=this.src+'?'" width="120" height="25"> <a href="javascript:CreateCheckCode.onclick">看不清，换一张</a></br> <input type="submit" value="登录"> </form> </body> </html>
后台验证的servlet代码：
1 package com.wqy.ValidateCode; 2 3 import java.io.IOException; 4 5 import javax.servlet.ServletException; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 10 public class LoginServlet extends HttpServlet { 11 public void doGet(HttpServletRequest request, HttpServletResponse response) 12 throws ServletException, IOException { 13 //获取前端传来的验证码 14 String name = request.getParameter("captcha"); 15 //从Attribute域中获取存放的验证码 16 String code = (String)request.getSession.getAttribute("code"); 17 //前后端验证码做比较。（验证码.toLowerCase是让它忽略大小写，这样在前端做验证的时候就不会因为大小写问题引发异常） 18 if(code.toLowerCase.equals(name.toLowerCase)){ 19 System.out.println("验证码正确"); 20 } 21 } 22 23 public void doPost(HttpServletRequest request, HttpServletResponse response) 24 throws ServletException, IOException { 25 doGet(request, response); 26 } 27 28 }
最终显示结果：