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package test; 




import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage;




import java.io.OutputStream;




import java.util.Random; 




import javax.imageio.ImageIO; 




import javax.servlet.http.HttpServlet;


import javax.servlet.http.HttpServletRequest; 


import javax.servlet.http.HttpServletResponse; 




public class ImageGenerator extends HttpServlet {




     private static final long serialVersionUID = -3938318741402322164L;   




     private static 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); 


     } 




     private static String charsLong = "23456789abcdefghjklmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ"; 


     private static String charsShort = "0123456789"; 


     private static String chars = charsLong;  




    @Override


     public void doGet(HttpServletRequest request, HttpServletResponse response) { 


         try { 


                int charsLength = chars.length(); 


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


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


                response.setDateHeader("Expires", 0); 


                int width = 70, height = 20;


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


                Graphics g = image.getGraphics(); 


                Random random = new Random(); 


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


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


                g.setFont(new Font("Times New Roman", Font.ITALIC, height)); 


                g.setColor(getRandColor(160, 200)); 


                for (int i = 0; i < 35; 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); 


                }


                StringBuilder sRand = new StringBuilder();


                String[] fontNames = { "Times New Roman", "Arial", "Book antiqua", "" }; 


                for (int i = 0; i < 4; i++) {


                      g.setFont(new Font(fontNames[random.nextInt(3)], Font.ITALIC, height)); 


                      char rand = chars.charAt(random.nextInt(charsLength)); 


                      sRand.append(rand);


                      g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110))); 


                      g.drawString(String.valueOf(rand), 16 * i + random.nextInt(6) + 3, height - random.nextInt(4)); 


                }


                g.setColor(getRandColor(160, 200));


                for (int i = 0; i < 30; i++) {


                      int x = random.nextInt(width); 


                      int y = random.nextInt(height); 


                      int xl = random.nextInt(width); 


                      int yl = random.nextInt(width); 


                      g.drawLine(x, y, x + xl, y + yl); 


                } 


                request.getSession().setAttribute("Login_Image_Code", sRand.toString()); 


                g.dispose(); 


                try {


                      Thread.sleep(100); 


                } catch (Exception ex) {      } 


                OutputStream os = response.getOutputStream();


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


                os.flush(); 


                os.close();


          } catch (Exception ex) {     }


      } 


} 

 修改 web.xml:

<servlet>


         <servlet-name>imageGenerator</servlet-name>


         <servlet-class>test.ImageGenerator</servlet-class>


</servlet>




<servlet-mapping>


         <servlet-name>imageGenerator</servlet-name>


         <url-pattern>/image.jsp</url-pattern>


</servlet-mapping> 

   转自：http://www.javaeedev.com/blog/article.jspx?articleId=ff808081198fb524011999d714b0066f