大家好，我用了一个网上的产生登录验证码的类。已经部署好了，但是运行的时候图片没有产生，是一个红叉。我把这个类贴出来，大家帮看看，浪费大家时间了，谢谢！

import java.io.*; 

import javax.servlet.*; 

import javax.servlet.http.*; 

import java.awt.*; 

import java.awt.image.*; 

import javax.imageio.ImageIO; 

 

public class CheckCodeServlet extends HttpServlet 

{ 

       private static int WIDTH = 60; 

       private static int HEIGHT = 20; 

       public void doGet(HttpServletRequest request,HttpServletResponse response) 

                     throws ServletException,IOException 

       {            

              HttpSession session = request.getSession(); 

              response.setContentType("image/jpeg"); 

              ServletOutputStream sos = response.getOutputStream(); 

 

              // 设置浏览器不要缓存此图片 

              response.setHeader("Pragma","No-cache"); 

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

              response.setDateHeader("Expires", 0); 

              

              // 创建内存图象并获得其图形上下文 

              BufferedImage image = 

                     new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); 

              Graphics g = image.getGraphics(); 

              

              // 产生随机的认证码 

              char [] rands = generateCheckCode(); 

              

              // 产生图像 

              drawBackground(g); 

              drawRands(g,rands); 

              

              // 结束图像 的绘制 过程， 完成图像 

              g.dispose(); 

              

              
                  // 将图像输出到客户端 

              ByteArrayOutputStream bos = new ByteArrayOutputStream(); 

              ImageIO.write(image, "JPEG", bos); 

              byte [] buf = bos.toByteArray(); 

              response.setContentLength(buf.length); 

              // 下面的语句也可写成： bos.writeTo(sos); 

              sos.write(buf); 

              bos.close(); 

              sos.close(); 

 

              // 将当前验证码存入到 Session 中 

              session.setAttribute("check_code",new String(rands)); 

              // 直接使用下面的代码将有问题， Session 对象必须在提交响应前获得 

              //request.getSession().setAttribute("check_code",new String(rands)); 

       } 

       

       private char [] generateCheckCode() 

       { 

              // 定义验证码的字符表 

              String chars = "0123456789abcdefghijklmnopqrstuvwxyz"; 

              char [] rands = new char[4]; 

              for(int i=0; i<4; i++) 

              { 

                     int rand = (int)(Math.random() * 36); 

                     rands[i] = chars.charAt(rand); 

              } 

              return rands; 

       } 

       

       private void drawRands(Graphics g , char [] rands) 

       { 

              g.setColor(Color.BLACK); 

              g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18)); 

              // 在不同的高度上输出验证码的每个字符          

              g.drawString("" + rands[0],1,17); 

              g.drawString("" + rands[1],16,15); 

              g.drawString("" + rands[2],31,18); 

              g.drawString("" + rands[3],46,16); 

              System.out.println(rands); 

       } 

       

       private void drawBackground(Graphics g) 

       { 

             // 画背景 

              g.setColor(new Color(0xDCDCDC)); 

              g.fillRect(0, 0, WIDTH, HEIGHT); 

              // 随机产生 120 个干扰点 

              for(int i=0; i<120; i++) 

              { 

                     int x = (int)(Math.random() * WIDTH); 

                     int y = (int)(Math.random() * HEIGHT); 

                     int red = (int)(Math.random() * 255); 

                     int green = (int)(Math.random() * 255); 

                     int blue = (int)(Math.random() * 255); 

                     g.setColor(new Color(red,green,blue));        

                     g.drawOval(x,y,1,0); 

              } 

       } 

}