JSP图片验证码
产生图片验证码的Servlet:package web;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.OutputStream;import java.util.Random;import javax.imageio.ImageIO;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 ValidationCode extends HttpServlet {/** * 验证码的字符集合。 */private static String codeChars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";/** * 产生随机的颜色 * @param minColor * @param maxColor * @return */private static Color getRandomColor(int minColor,int maxColor){Random r = new Random();int red = minColor + r.nextInt(maxColor-minColor);int green = minColor + r.nextInt(maxColor-minColor);int blue = minColor + r.nextInt(maxColor-minColor);return new Color(red,green,blue);}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//关闭客户端浏览器的缓冲区。response.setHeader("ragma", "No-cache");response.setHeader("Cache-Control", "no-cache");response.setHeader("Expirse", "0");//设置图形大小。int width = 90 , height = 20;//建立图形缓冲区。BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);Graphics g = image.getGraphics();//获得Graphics 对象。g.setColor(getRandomColor(180, 250));//设置背景色。g.fillRect(0, 0, width, height);//填充背景。StringBuilder validationCode = new StringBuilder();//用于保存最后的验证码String[] fontNames = {"Times New Roman","Book antiqua","Arial"};//用于随机的字体的集合Random r = new Random();//随机生成3-5个验证码for(int i = 0; i<3+r.nextInt(3); i++){g.setFont(new Font(fontNames , Font.ITALIC , height));char codeChar = codeChars.charAt(r.nextInt(codeChars.length()));validationCode.append(codeChar);g.setColor(getRandomColor(10, 100));g.drawString(String.valueOf(codeChar), 16 * i+ r.nextInt(7) ,height - r.nextInt(6));//在图形上输出验证码}//随机生干扰码for(int i = 0; i<30 ; i++){g.setColor(getRandomColor(90, 200));int x = r.nextInt(width);int y = r.nextInt(height);g.drawLine(x,y , x+r.nextInt(10), y+r.nextInt(5));}HttpSession session = request.getSession();//得到HttpSession对象session.setMaxInactiveInterval(10*60);//设置session对象10分钟失效。session.setAttribute("validation_code", validationCode.toString());//将验证码保存在session中g.dispose();//关闭Graphics对象OutputStream os = response.getOutputStream();//得到输出流ImageIO.write(image, "JPEG", os);//以JPEG格式向客户端发送图形验证码}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}检测验证码是否正确的方法：
/** * 核对用户输入的验证码是否合法 ** @param request * @param validationCode * @return */private boolean checkValidationCode(HttpServletRequest request,String validationCode) {// 从HttpSession中获得系统随机生成的验证码String validationCodeSession = (String) request.getSession().getAttribute("validation_code");// 如果获得的验证码为null，说明难码过期，必须刷新客户端重新获取if (validationCodeSession == null) {request.setAttribute("info", "验证码过期");return false;}// 输入的验证码不匹配if (!validationCode.equalsIgnoreCase(validationCodeSession)) {request.setAttribute("info", "验证码不正确！");return false;}return true;}
JSP页面：使用图形验证码的方法非常简单，只需将“validationCode”（产生验证码的Servlet的url-pattern）作为<img>标签的src属性值即可
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head> <base href="<%=basePath%>"><title>注册</title><script type="text/javascript">//重新获得验证码function refresh() {var img = document.getElementById("img_code");img.src = "validationCode?" + Math.random();//加随机参数，以保证每次的src属性都不同}</script></head><body><form action="register" method="post"><center>用 户 名：<input type="text" name="userName"><br />密 码：<input type="password" name="pwd"><br />确认密码：<input type="password" name="pwd2"><br />邮 箱：<input type="text" name="email"><br />验 证 码：<input type="text" name="validation_code"><img title="单击刷新" alt="验证码" src="validationCode" id="img_code" ><br /><input type="submit" value="注册"><input type="reset" value="重置"></center></form></body></html>
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