<form action="action.jsp" method="POST"> 
 <label> 用戶名： 
 <input type="text" name="name" data-singleTips="請(qǐng)輸入用戶名" value="admin" /> 
 </label> 
 <label> 密碼： <input type="password" name="password" /> 
 </label> 
 <!-- 驗(yàn)證碼 --> 
 <label class="captchaCode"> 
 驗(yàn)證碼： <img src="img.jsp" style="cursor: pointer;" onclick="this.src=this.src + '?' + new Date().valueOf();" /> 
 <input type="text" name="captchaImgCode" /> 
 </label> 
 <div> 
 <input type="submit" value="登錄" /> 
 
 </div> 
</form> 

<%@include file="captcha.jsp"%> 
<% 
 init(pageContext);// 加載圖片 
%> 

<%@page pageEncoding="UTF-8"%> 
<%@include file="captcha.jsp"%> 
<% 
 String captchaImgCode = request.getParameter("captchaImgCode"); 
 try { 
 if (isPass(pageContext, captchaImgCode)) { 
 out.println("驗(yàn)證碼通過(guò)！"); 
 } 
 } catch (Throwable e) { 
 out.println(e); 
 } 
%> 

<%@page pageEncoding="UTF-8" import="java.io.IOException, java.awt.*, java.awt.image.BufferedImage, java.util.Random, javax.imageio.ImageIO"%> 
<%! 
 // 定義Captcha 類 
 public static class Captcha { 
 /** 
 * 默認(rèn)寬度 60 
 */ 
 private int width = 60; 
 
 /** 
 * 默認(rèn)高度 20 
 */ 
 private int height = 20; 
 
 /** 
 * 驗(yàn)證碼 
 */ 
 private String code; 
 
 /** 
 * 生成驗(yàn)證碼圖片 
 * 
 * @return 圖片對(duì)象 
 */ 
 public BufferedImage get() { 
 BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);// 在內(nèi)存中創(chuàng)建圖像 
 Graphics g; 
 
 g = image.getGraphics(); // 獲取圖形上下文 
 g.setColor(getRandColor(200, 250)); // 設(shè)定背景 
 g.fillRect(0, 0, width, height); 
 g.setFont(new Font("Times New Roman", Font.PLAIN, 18)); // 設(shè)定字體 
 g.setColor(getRandColor(160, 200)); 
 
 Random random = new Random();// 隨機(jī)產(chǎn)生干擾線 
 for (int i = 0; i < 155; i++) { 
 int x = random.nextInt(width), y = random.nextInt(height); 
 int xl = random.nextInt(12), yl = random.nextInt(12); 
 g.drawLine(x, y, x + xl, y + yl); 
 } 
 
 String sRand = ""; // 隨機(jī)產(chǎn)生4位驗(yàn)證碼 
 for (int i = 0; i < 4; i++) { 
 String rand = String.valueOf(random.nextInt(10)); 
 sRand += rand; 
 g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110))); // 將認(rèn)證碼顯示到圖象中 
 g.drawString(rand, 13 * i + 6, 16);// 調(diào)用函數(shù)出來(lái)的顏色相同，可能是因?yàn)榉N子太接近，所以只能直接生成 
 } 
 
 // 將認(rèn)證碼存入SESSION 
 // session.setAttribute("rand", sRand); 
 setCode(sRand); 
 g.dispose();// 圖象生效 
 
 return image; 
 } 
 
 /** 
 * 生成隨機(jī)顏色 
 * 
 * @param fc 
 * @param bc 
 * @return 
 */ 
 private Color getRandColor(int fc, int bc) { 
 if (fc > 255) 
 fc = 255; 
 if (bc > 255) 
 bc = 255; 
 
 Random random = new Random(); 
 int r = fc + random.nextInt(bc - fc); 
 int g = fc + random.nextInt(bc - fc); 
 int b = fc + random.nextInt(bc - fc); 
 
 return new Color(r, g, b); 
 } 
 
 /** 
 * 獲取高度 
 * 
 * @return 
 */ 
 public int getHeight() { 
 return height; 
 } 
 
 /** 
 * 設(shè)置高度 
 * 
 * @param height 
 * 高度 
 */ 
 public void setHeight(int height) { 
 this.height = height; 
 } 
 
 /** 
 * 獲取驗(yàn)證碼 
 * 
 * @return 
 */ 
 public String getCode() { 
 return code; 
 } 
 
 /** 
 * 設(shè)置驗(yàn)證碼 
 * 
 * @param code 
 * 驗(yàn)證碼 
 */ 
 public void setCode(String code) { 
 this.code = code; 
 } 
 
 /** 
 * 獲取寬度 
 * 
 * @return 
 */ 
 public int getWidth() { 
 return width; 
 } 
 
 /** 
 * 設(shè)置寬度 
 * 
 * @param width 
 * 寬度 
 */ 
 public void setWidth(int width) { 
 this.width = width; 
 } 
 
 } 
 
 
 /** 
 * SESSION 的鍵值 
 */ 
 public static final String SESSION_KEY = "rand"; 
 
 /** 
 * 顯示驗(yàn)證碼圖片并將認(rèn)證碼存入 Session 
 * 
 * @param response 
 * 響應(yīng)對(duì)象 
 * @param session 
 * 會(huì)話對(duì)象 
 */ 
 public static void init(HttpServletResponse response, HttpSession session) { 
 Captcha img = new Captcha(); 
 
 // 不用緩存 
 response.setHeader("Pragma", "No-cache"); 
 response.setHeader("Cache-Control", "no-cache"); 
 response.setDateHeader("Expires", 0); 
 response.setContentType("image/jpg"); 
 
 try { 
 ImageIO.write(img.get(), "JPEG", response.getOutputStream()); 
 
 /* 
 * 加上下面代碼,運(yùn)行時(shí)才不會(huì)出現(xiàn)java.lang.IllegalStateException: getOutputStream() has already been called ..........等異常 
 * response.getOutputStream().flush(); 
 * response.getOutputStream().close(); 
 * response.flushBuffer(); 
 */ 
 
 // JSP內(nèi)置對(duì)象out和response.getWrite()的區(qū)別，兩者的主要區(qū)別：1. 這兩個(gè)對(duì)象的類型是完全不同的…… 
 // response.getWriter(); 
 // http://blog.sina.com.cn/s/blog_7217e4320101l8gq.html 
 // http://www.dbjr.com.cn/kf/201109/103284.html 
 
 // pageContext.getOut().clear(); 
 } catch (IOException e) { 
 e.printStackTrace(); 
 } 
 
 session.setAttribute(SESSION_KEY, img.getCode()); // 將認(rèn)證碼存入 SESSION 
 System.out.println("生成驗(yàn)證碼:" + img.getCode()); 
 } 
 
 /** 
 * 顯示驗(yàn)證碼圖片并將認(rèn)證碼存入 Session（For JSP） 
 * 
 * @param pageContext 
 * 頁(yè)面上下文對(duì)象 
 */ 
 public static void init(PageContext pageContext) { 
 init((HttpServletResponse) pageContext.getResponse(), pageContext.getSession()); 
 } 
 
 
 /** 
 * 判斷用戶輸入的驗(yàn)證碼是否通過(guò) 
 * 
 * @param pageContext 
 * 頁(yè)面上下文對(duì)象 
 * @return true 表示通過(guò) 
 * @throws Throwable 
 */ 
 public static boolean isPass(PageContext pageContext, String code) throws Throwable { 
 boolean isCaptchaPass = false; 
 
 String rand = (String) pageContext.getSession().getAttribute(SESSION_KEY); 
 
 System.out.println("rand:" + rand); 
 System.out.println("CaptchaCode:" + code); 
 
 if (rand == null) 
 throw new UnsupportedOperationException("請(qǐng)刷新驗(yàn)證碼。"); 
 else if (code == null || code.equals("")) { 
 throw new IllegalArgumentException("沒提供驗(yàn)證碼參數(shù)"); 
 } else { 
 isCaptchaPass = rand.equals(code); 
 if (!isCaptchaPass) 
 throw new IllegalAccessError("驗(yàn)證碼不正確"); 
 } 
 
 return isCaptchaPass; 
 } 
%>