首页 > 代码库 > servlet实现一次性验证码
servlet实现一次性验证码
大致的思路:先用java生成验证码,然后将生成的验证码保存到session中,在表单提交时,将保存到session中的验证码与表单提交的验证码进行比较,然后输出不同的结果。其实还可以实现一个目标,在用户禁用cookie也能验证成功,那就需要url重写了。这个例子只是给了一个简单的验证码的实现,当然可以根据实际的需求写出更加精彩的验证码,比如“汉字”验证码,算术验证码。本文只是给怎样实现验证码提供了一个基本的思路。
ImageCodeUtil.java
package cn.zq.util; import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.FileOutputStream; import java.io.OutputStream; import java.util.Random; import javax.imageio.ImageIO; /** * 图形码工具类 * @author zq */ public class ImageCodeUtil { /** * 下面配置的这些常量,最好的办法就是通过配置文件来获取,下面直接写死了 */ /** * 图形码的宽 */ private static final int IMAGE_CODE_WIDTH = 120; /** * 图形码的高 */ private static final int IMAGE_CODE_HEIGHT = 60; /** * 图形码个数 */ private static final int IMAGE_CODE_NUM = 4; /** * 图形码最多干扰线数量 */ private static final int IMAGE_CODE_MAX_LINE_NUM = 15; /** * 图形码最小干扰线数量 */ private static final int IMAGE_CODE_MIN_LINE_NUM = 10; /** * 图片类型 */ private static final String IMAGE_TYPE = "jpg"; /** * 图形码取数 */ private static final String IMAGE_CODE_DATA = http://www.mamicode.com/"ABCDEFGHIJKLMNOPQRSJUVWXYZabcdefghijklmnopqrsjuvwxyz0123456789";>GetImageCodeServlet.java
package cn.zq.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import cn.zq.util.ImageCodeUtil; public class GetImageCodeServlet extends HttpServlet { private static final long serialVersionUID = 5225185955711424724L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //设置浏览器不要缓存 response.setHeader("pragma", "no-cache"); response.setHeader("cache-control", "no-cache"); response.setHeader("expires", "0"); response.setContentType("image/jpeg"); HttpSession session = request.getSession(); ServletOutputStream sos = response.getOutputStream(); String code = ImageCodeUtil.generateSimpleImageCode(sos); session.setAttribute("imageCode", code); } }
FormServlet.javapackage cn.zq.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 javax.servlet.http.HttpSession; public class FormServlet extends HttpServlet { private static final long serialVersionUID = -5699696644228229140L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html; charset=UTF-8"); //获取客户端提交的图像码 String clientImageCode = request.getParameter("imageCode"); HttpSession session = request.getSession(); //获取服务器端的图像码 String serverImageCode = (String) session.getAttribute("imageCode"); PrintWriter out = response.getWriter(); if(serverImageCode != null){ if(serverImageCode.equalsIgnoreCase(clientImageCode)){ out.print("已经通过验证!"); }else{ out.print("验证码输入有误"); } session.removeAttribute("imageCode"); }else{ out.print("验证码失效!"); } } }form.html<span style="color:#000000;"><!DOCTYPE html> <html> <head> <title>输入验证码</title> </head> <body> <form action="formServlet" method="post"> <input type="text" name="imageCode"><img src=http://www.mamicode.com/"getImageCodeServlet" border="1px">
>web.xml文件的有关配置:<span style="color:#000000;"><?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <servlet> <servlet-name>GetImageCodeServlet</servlet-name> <servlet-class>cn.zq.servlet.GetImageCodeServlet</servlet-class> </servlet> <servlet> <servlet-name>FormServlet</servlet-name> <servlet-class>cn.zq.servlet.FormServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>GetImageCodeServlet</servlet-name> <url-pattern>/getImageCodeServlet</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>FormServlet</servlet-name> <url-pattern>/formServlet</url-pattern> </servlet-mapping> </web-app></span>
与验证码类似的经典问题有,怎样防止表单重复提交,这类问题很有意思,防止表单提交的要点就是在表单用隐藏域保存从服务器端获取的值,当表单提交时,拿这个值与服务器端的值进行比较。大致的思路与验证码很类型,都是在服务器端存放值,在从客户浏览器表单提交时获取客户端的值进行比较。源代码可以再这里下载
servlet实现一次性验证码
声明:以上内容来自用户投稿及互联网公开渠道收集整理发布,本网站不拥有所有权,未作人工编辑处理,也不承担相关法律责任,若内容有误或涉及侵权可进行投诉: 投诉/举报 工作人员会在5个工作日内联系你,一经查实,本站将立刻删除涉嫌侵权内容。