struts2 实现随机验证码
action中的代码：

@Controller(value = "randomPictureAction")public class RandomPictureAction extends BaseAction {private static final long serialVersionUID = -6950908478971552308L;   private ByteArrayInputStream inputStream;     public String execute() throws Exception {      // 在内存中创建图象          int width = 85, height = 20;            BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);            // 获取图形上下文          Graphics g = image.getGraphics();             // 生成随机类          Random random = new Random();            // 设定背景色          g.setColor(getRandColor(200, 250));          g.fillRect(0, 0, width, height);            // 设定字体          g.setFont(new Font("Times New Roman", Font.PLAIN, 18));            // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到          g.setColor(getRandColor(160, 200));          for (int i = 0; i < 155; i++) {           int x = random.nextInt(width);              int y = random.nextInt(height);              int xl = random.nextInt(12);              int yl = random.nextInt(12);              g.drawLine(x, y, x + xl, y + yl);          }             // 取随机产生的认证码(6位数字)           String sRand = "";           for (int i = 0; i < 6; i++) {              String rand = String.valueOf(random.nextInt(10));              sRand += rand;              // 将认证码显示到图象中              g.setColor(new Color(20 + random.nextInt(110), 20 + random                       .nextInt(110), 20 + random.nextInt(110)));               // 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               g.drawString(rand, 13 * i + 6, 16);           }             // 将认证码存入SESSION           ActionContext.getContext().getSession().put("rand", sRand);        //this.getRequest().setAttribute("rand", sRand);        this.str = sRand;        System.out.println("rand="+sRand);        // 图象生效           g.dispose();           ByteArrayOutputStream output = new ByteArrayOutputStream();           ImageOutputStream imageOut = ImageIO.createImageOutputStream(output);           ImageIO.write(image, "JPEG", imageOut);           imageOut.close();           ByteArrayInputStream input = new ByteArrayInputStream(output   .toByteArray());           this.setInputStream(input);           return SUCCESS; }         /*       * 给定范围获得随机颜色       */      private Color getRandColor(int fc, int bc) {           Random random = new Random();           if (fc > 255)               fc = 255;           if (bc > 255)               bc = 255;           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);       }         public void setInputStream(ByteArrayInputStream inputStream) {           this.inputStream = inputStream;       }         public ByteArrayInputStream getInputStream() {           return inputStream;       }}

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"    "http://struts.apache.org/dtds/struts-2.0.dtd"><!-- Struts2配置文件 --><struts><!-- 景阳岗酒业客户留言管理 -->   <package name="randpicture" namespace="/" extends="struts-default,json-default"><!-- 工具action --><action name="rand" type="stream"><param name="contentType">image/jpeg</param>  <param name="inputName">inputStream</param>    </result></action></package></struts>

<script type="text/javascript"> function changeValidateCode(obj) {       var currentTime= new Date().getTime();    obj.src = "rand?d=" + currentTime;}</script>

<img src="rand" onclick="changeValidateCode(this)" />