JSP实用教程之简易图片验证码的实现方法（附源

<form action="action.jsp" method="POST"> 
 <label> 用户名 
 <input type="text" name="name" data-singleTips="请输入用户名" value="admin" /> 
 </label> 
 <label> 密码 <input type="password" name="password" /> 
 </label> 
 <!-- 验证码 --> 
 <label class="captchaCode"> 
 验证码 <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="登录" /> 
 
 </div> 
</form> 

<%@include file="captcha.jsp"%> 
<% 
 init(pageContext);// 加载图片 
%> 

<%@page pageEncoding="UTF-8"%> 
<%@include file="captcha.jsp"%> 
<% 
 String captchaImgCode = request.getParameter("captchaImgCode"); 
 try { 
 if (isPass(pageContext, captchaImgCode)) { 
 out.println("验证码通过！"); 
 } 
 } 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"%> 
<%! 
 // 定义Captcha 类 
 public static class Captcha { 
 / 
  默认宽度 60 
 / 
 private int width = 60; 
 
 / 
  默认高度 20 
 / 
 private int height = 20; 
 
 / 
  验证码 
 / 
 private String code; 
 
 / 
  生成验证码图片 
  
  @return 图片对象 
 / 
 public BufferedImage get() { 
 BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);// 在内存中创建图像 
 Graphics g; 
 
 g = image.getGraphics(); // 获取图形上下文 
 g.setColor(getRandColor(200, 250)); // 设定背景 
 g.fillRect(0, 0, width, height); 
 g.setFont(new Font("Times New Roman", Font.PLAIN, 18)); // 设定字体 
 g.setColor(getRandColor(160, 200)); 
 
 Random random = new Random();// 随机产生干扰线 
 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 = ""; // 随机产生4位验证码 
 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))); // 将认证码显示到图象中 
 g.drawString(rand, 13  i + 6, 16);// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成 
 } 
 
 // 将认证码存入SESSION 
 // session.setAttribute("rand", sRand); 
 setCode(sRand); 
 g.dispose();// 图象生效 
 
 return image; 
 } 
 
 / 
  生成随机颜色 
  
  @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); 
 } 
 
 / 
  获取高度 
  
  @return 
 / 
 public int getHeight() { 
 return height; 
 } 
 
 / 
  设置高度 
  
  @param height 
  高度 
 / 
 public void setHeight(int height) { 
 this.height = height; 
 } 
 
 / 
  获取验证码 
  
  @return 
 / 
 public String getCode() { 
 return code; 
 } 
 
 / 
  设置验证码 
  
  @param code 
  验证码 
 / 
 public void setCode(String code) { 
 this.code = code; 
 } 
 
 / 
  获取宽度 
  
  @return 
 / 
 public int getWidth() { 
 return width; 
 } 
 
 / 
  设置宽度 
  
  @param width 
  宽度 
 / 
 public void setWidth(int width) { 
 this.width = width; 
 } 
 
 } 
 
 
 / 
  SESSION 的键值 
 / 
 public static final String SESSION_KEY = "rand"; 
 
 / 
  显示验证码图片并将认证码存入 Session 
  
  @param response 
  响应对象 
  @param session 
  会话对象 
 / 
 public static void init(HttpServletResponse response, HttpSession session) { 
 Captcha img = new Captcha(); 
 
 // 不用缓存 
 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()); 
 
 / 
  加上狼蚁网站SEO优化代码,运行时才不会出现java.lang.IllegalStateException: getOutputStream() has already been called ..........等异常 
  response.getOutputStream().flush(); 
  response.getOutputStream().close(); 
  response.flushBuffer(); 
 / 
 
 // JSP内置对象out和response.getWrite()的区别，两者的主要区别1. 这两个对象的类型是完全不同的…… 
 // response.getWriter(); 
 // http://blog.sina../s/blog_7217e4320101l8gq.html 
 // https://.jb51./kf/201109/103284.html 
 
 // pageContext.getOut().clear(); 
 } catch (IOException e) { 
 e.printStackTrace(); 
 } 
 
 session.setAttribute(SESSION_KEY, img.getCode()); // 将认证码存入 SESSION 
 System.out.println("生成验证码:" + img.getCode()); 
 } 
 
 / 
  显示验证码图片并将认证码存入 Session（For JSP） 
  
  @param pageContext 
  页面上下文对象 
 / 
 public static void init(PageContext pageContext) { 
 init((HttpServletResponse) pageContext.getResponse(), pageContext.getSession()); 
 } 
 
 
 / 
  判断用户输入的验证码是否通过 
  
  @param pageContext 
  页面上下文对象 
  @return true 表示通过 
  @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("请刷新验证码。"); 
 else if (code == null || code.equals("")) { 
 throw new IllegalArgumentException("没提供验证码参数"); 
 } else { 
 isCaptchaPass = rand.equals(code); 
 if (!isCaptchaPass) 
 throw new IllegalAessError("验证码不正确"); 
 } 
 
 return isCaptchaPass; 
 } 
%>