转自：http://www.cnblogs.com/wufengxyz/archive/2011/12/04/2275489.html
前言：
为了防止用户恶意,或者使用软件外挂提交一些内容,就得用验证码来阻止,虽然这个会影响用户体验,但为了避免一些问题很多网站都使用了验证码;今天下午参 考文档弄了一个验证码,这里分享一下;这是一个web工程,首先是页面,这里只是一个显示验证码页面index.jsp,使用默认生成的就可以了,表单没 有做提交,如下：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>验证码</title> <script type="text/javascript"> function refresh(obj) { obj.src = "imageServlet?"+Math.random(); } </script> </head> <body> <form action="checkServlet" method="post"> <label>输入验证码</label><br/> <input type="text" name="randomCode"/><img title="点击更换" onclick="javascript:refresh(this);" src="imageServlet"><br/> <input type="submit" value="submit"> </form> </body> </html>
下面是后台代码,这里是一个Servlet,不要忘记在web.xml中配置请求url：
package com.wf.web; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ImageServlet extends HttpServlet { private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("image/jpeg");//设置相应类型,告诉浏览器输出的内容为图片 response.setHeader("Pragma", "No-cache");//设置响应头信息，告诉浏览器不要缓存此内容 response.setHeader("Cache-Control", "no-cache"); response.setDateHeader("Expire", 0); RandomValidateCode randomValidateCode = new RandomValidateCode(); try { randomValidateCode.getRandcode(request, response);//输出图片方法 } catch (Exception e) { e.printStackTrace(); } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
这个类是生成验证码的方法,如下：
package com.wf.web; import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.util.Random; import javax.imageio.ImageIO; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class RandomValidateCode { public static final String RANDOMCODEKEY = "RANDOMVALIDATECODEKEY";//放到session中的key private Random random = new Random(); private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生的字符串 private int width = 80;//图片宽 private int height = 26;//图片高 private int lineSize = 40;//干扰线数量 private int stringNum = 4;//随机产生字符数量 /* * 获得字体 */ private Font getFont(){ return new Font("Fixedsys",Font.CENTER_BASELINE,18); } /* * 获得颜色 */ private Color getRandColor(int fc,int bc){ if(fc > 255) fc = 255; if(bc > 255) bc = 255; int r = fc + random.nextInt(bc-fc-16); int g = fc + random.nextInt(bc-fc-14); int b = fc + random.nextInt(bc-fc-18); return new Color(r,g,b); } /** * 生成随机图片 */ public void getRandcode(HttpServletRequest request, HttpServletResponse response) { HttpSession session = request.getSession(); //BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类 BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR); Graphics g = image.getGraphics();//产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作 g.fillRect(0, 0, width, height); g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,18)); g.setColor(getRandColor(110, 133)); //绘制干扰线 for(int i=0;i<=lineSize;i++){ drowLine(g); } //绘制随机字符 String randomString = ""; for(int i=1;i<=stringNum;i++){ randomString=drowString(g,randomString,i); } session.removeAttribute(RANDOMCODEKEY); session.setAttribute(RANDOMCODEKEY, randomString); System.out.println(randomString); g.dispose(); try { ImageIO.write(image, "JPEG", response.getOutputStream());//将内存中的图片通过流动形式输出到客户端 } catch (Exception e) { e.printStackTrace(); } } /* * 绘制字符串 */ private String drowString(Graphics g,String randomString,int i){ g.setFont(getFont()); g.setColor(new Color(random.nextInt(101),random.nextInt(111),random.nextInt(121))); String rand = String.valueOf(getRandomString(random.nextInt(randString.length()))); randomString +=rand; g.translate(random.nextInt(3), random.nextInt(3)); g.drawString(rand, 13*i, 16); return randomString; } /* * 绘制干扰线 */ private void drowLine(Graphics g){ int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(13); int yl = random.nextInt(15); g.drawLine(x, y, x+xl, y+yl); } /* * 获取随机的字符 */ public String getRandomString(int num){ return String.valueOf(randString.charAt(num)); } }
这里附带吧web.xml也加上吧,希望对初学者有帮助
<?xml version="1.0" encoding="UTF-8"?> <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <servlet> <servlet-name>ImageServlet</servlet-name> <servlet-class>com.wf.web.ImageServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ImageServlet</servlet-name> <url-pattern>/imageServlet</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
就这么多,验证码是保存在session中的,或者cookie也行,但都要必须及时清除。