验证码功能

来源：互联网发布：刷手游元宝软件编辑：程序博客网时间：2024/06/03 23:50

新建一个servlet

package Servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import cn.dsna.util.images.ValidateCode;public class ServletDemo4 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//告诉浏览器不缓存（这样在地址栏刷新网址就会换验证码）,处理不同浏览器不缓存的方法。 这个配置信息在新建默认的index里面就有。response.setHeader("pragna", "no-cach");response.setHeader("cache-control", "no-cache");response.setHeader("exprirs", "0");  ValidateCode vc=new ValidateCode(110, 25, 4, 9);//要在lib导入一个包：ValidateCode  vc.write(response.getOutputStream()); } public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);} }

新建表单

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title> 表单登录实现验证码功能</title></head><script type="text/javascript">function changeCode(){  //得到图片元素    var img = document.getElementsByTagName("img")[0];//  var img = Document().getElementsByTagName("img");这种不知道为什么不行    img.src="/WebTest/ServletDemo4?time="+new Date().getTime();}</script><body><form action="#" method="post">用户名：<input type="text" name="userName"/><br/>密码：<input type="password" name="pwd" /><br/>验证码：<input type="text" name="code"/>     <img src="/WebTest/ServletDemo4" onclick="changeCode()"/><a href="javascript:changeCode()">看不清，换一张</a><br/>     <input type="submit" value="提交"/></form></body></html>

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