var imgCheckValid = new Ext.create('Ext.Component',{

         width: 70, //图片宽度

         height: 45, //图片高度

         margin:'5',

         id:"imd_imgCheckValid",

         autoEl: {

             tag: 'img',    //指定为img标签

             src: 'Code/genCodeImg.do?'    //指定url路径

         },

         listeners: {

             render: function(component){

                   component.getEl().on('click', function(e){

                      this.dom.src = 'Code/genCodeImg.do?'+(new Date().getTime());  // autoEl不会自动加载，只有设置了不同的src才会加载

                 });

              }

         }

     });

     <!-- 客户端 -->

     <package name="Code" extends="json" namespace="/Code">

         <action name="genCodeImg" class="codeAction" method="genCodeImg">

             <result name="success" type="json">

                 <param name="root">responseJson</param>

             </result>

         </action>

     </package>

 import java.awt.Color;

 import java.awt.Font;

 import java.awt.Graphics;

 import java.awt.image.BufferedImage;

 import java.util.Map;

 import java.util.Random;

 import javax.imageio.ImageIO;

 import javax.servlet.ServletOutputStream;

 import javax.servlet.http.HttpServletResponse;

 import org.apache.struts2.ServletActionContext;

 import com.common.core.st2.action.BaseAction;

 import com.opensymphony.xwork2.ActionContext;

 import com.sinsche.i.action.ICodeAction;

 public class CodeAction extends BaseAction implements  ICodeAction {

     /**

      *

      */

     private static final long serialVersionUID = 6865491407475710154L;

     private boolean success;

     private String message;

     // 图片的宽度。

     private int width = 70;

     // 图片的高度。

     private int height = 45;

     // 验证码字符个数

     private int codeCount = 4;

     // 验证码干扰线数

     private int lineCount = 20;

     // 验证码图片Buffer

     private BufferedImage buffImg = null;

     Random random = new Random();

     public String genCodeImg() throws Exception {

         HttpServletResponse resp = ServletActionContext.getResponse();

         int fontWidth = width / codeCount;// 字体的宽度

         int fontHeight = height - 5;// 字体的高度

         int codeY = height - 8;

         // 图像buffer

         buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

         Graphics g = buffImg.getGraphics();

         // Graphics2D g = buffImg.createGraphics();

         // 设置背景色

         g.setColor(getRandColor(200, 250));

         g.fillRect(0, 0, width, height);

         // 设置字体

         // Font font1 = getFont(fontHeight);

         Font font = new Font("Fixedsys", Font.BOLD, fontHeight);

         g.setFont(font);

         // 设置干扰线

         for (int i = 0; i < lineCount; i++) {

             int xs = random.nextInt(width);

             int ys = random.nextInt(height);

             int xe = xs + random.nextInt(width);

             int ye = ys + random.nextInt(height);

 //            g.setColor(getRandColor(1, 255));

             shear(g,1,20,getRandColor(1, 255));

             g.drawLine(xs, ys, xe, ye);

         }

         // 添加噪点

         float yawpRate = 0.01f;// 噪声率

         int area = (int) (yawpRate * width * height);

         for (int i = 0; i < area; i++) {

             int x = random.nextInt(width);

             int y = random.nextInt(height);

             buffImg.setRGB(x, y, random.nextInt(255));

         }

         String str1 = randomStr(codeCount);// 得到随机字符

         for (int i = 0; i < codeCount; i++) {

             String strRand = str1.substring(i, i + 1);

             g.setColor(getRandColor(1, 255));

             // g.drawString(a,x,y);

             // a为要画出来的东西，x和y表示要画的东西最左侧字符的基线位于此图形上下文坐标系的 (x, y) 位置处

             g.drawString(strRand, i * fontWidth + 3, codeY);

         }

         // 将四位数字的验证码保存到Session中。

         Map<String, Object> map = ActionContext.getContext().getSession();

         System.out.print(str1);

         map.put("code", str1.toString());

         // 禁止图像缓存。

         resp.setHeader("Pragma", "no-cache");

         resp.setHeader("Cache-Control", "no-cache");

         resp.setDateHeader("Expires", 0);

         resp.setContentType("image/jpeg");

         // 将图像输出到Servlet输出流中。

         ServletOutputStream sos = resp.getOutputStream();

         ImageIO.write(buffImg, "jpeg", sos);

         sos.close();

         return null;

     }

     // 得到随机字符

     private String randomStr(int n) {

         String str1 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";

         String str2 = "";

         int len = str1.length() - 1;

         double r;

         for (int i = 0; i < n; i++) {

             r = (Math.random()) * len;

             str2 = str2 + str1.charAt((int) r);

         }

         return str2;

     }

     // 得到随机颜色

     private Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色

         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);

     }

 //    /**

 //     * 产生随机字体

 //     */

 //    private Font getFont(int size) {

 //        Font font[] = new Font[5];

 //        font[0] = new Font("Ravie", Font.PLAIN, size);

 //        font[1] = new Font("Antique Olive Compact", Font.PLAIN, size);

 //        font[2] = new Font("Fixedsys", Font.PLAIN, size);

 //        font[3] = new Font("Wide Latin", Font.PLAIN, size);

 //        font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, size);

 //        return font[random.nextInt(5)];

 //    }

     // 扭曲方法

     private void shear(Graphics g, int w1, int h1, Color color) {

         shearX(g, w1, h1, color);

         shearY(g, w1, h1, color);

     }

     private void shearX(Graphics g, int w1, int h1, Color color) {

         int period = random.nextInt(2);

         boolean borderGap = true;

         int frames = 1;

         int phase = random.nextInt(2);

         for (int i = 0; i < h1; i++) {

             double d = (double) (period >> 1) * Math.sin((double) i / (double) period + (6.2831853071795862D * (double) phase) / (double) frames);

             g.copyArea(0, i, w1, 1, (int) d, 0);

             if (borderGap) {

                 g.setColor(color);

                 g.drawLine((int) d, i, 0, i);

                 g.drawLine((int) d + w1, i, w1, i);

             }

         }

     }

     private void shearY(Graphics g, int w1, int h1, Color color) {

         int period = random.nextInt(40) + 10; // 50;

         boolean borderGap = true;

         int frames = 20;

         int phase = 7;

         for (int i = 0; i < w1; i++) {

             double d = (double) (period >> 1) * Math.sin((double) i / (double) period + (6.2831853071795862D * (double) phase) / (double) frames);

             g.copyArea(i, 0, 1, h1, 0, (int) d);

             if (borderGap) {

                 g.setColor(color);

                 g.drawLine(i, (int) d, i, 0);

                 g.drawLine(i, (int) d + h1, i, h1);

             }

         }

     }

     public BufferedImage getBuffImg() {

         return buffImg;

     }

     @Override

     public String list() throws Exception {

         return null;

     }

     @Override

     public String create() throws Exception {

         return null;

     }

     @Override

     public String update() throws Exception {

         return null;

     }

     @Override

     public String delete() throws Exception {

         return null;

     }

     @Override

     public String listByPage() throws Exception {

         return null;

     }

     public boolean isSuccess() {

         return success;

     }

     public void setSuccess(boolean success) {

         this.success = success;

     }

     public String getMessage() {

         return message;

     }

     public void setMessage(String message) {

         this.message = message;

     }

 }