<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %><%!Color getRandColor(int fc,int bc){//給定范圍獲得隨機顏色    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);    }%><%//設置頁面不緩存response.setHeader("Pragma","No-cache");response.setHeader("Cache-Control","no-cache");response.setDateHeader("Expires", 0);// 在內存中創建圖象int width=60, height=20;BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);// 獲取圖形上下文Graphics g = image.getGraphics();//生成隨機類Random random = new Random();// 設定背景色g.setColor(getRandColor(200,250));g.fillRect(0, 0, width, height);//設定字體g.setFont(new Font("Times New Roman",Font.PLAIN,18));//畫邊框//g.setColor(new Color());//g.drawRect(0,0,width-1,height-1);// 隨機產生155條干擾線，使圖象中的認證碼不易被其它程序探測到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);}// 取隨機產生的認證碼(4位數字)//String rand = request.getParameter("rand");//rand = rand.substring(0,rand.indexOf("."));String sRand="";for (int i=0;i<4;i++){  String rand=String.valueOf(random.nextInt(10));  sRand+=rand;  // 將認證碼顯示到圖象中  g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//調用函數出來的顏色相同，可能是因為種子太接近，所以只能直接生成  g.drawString(rand,13*i+6,16);}// 將認證碼存入SESSIONsession.setAttribute("rand",sRand);// 圖象生效g.dispose();// 輸出圖象到頁面ImageIO.write(image, "JPEG", response.getOutputStream());out.clear();out = pageContext.pushBody();%>