寫好的驗證界面(四位數數據隨機組合)

<%@ page contentType="image/jpeg" 
pageEncoding="GBK"
import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %> 
<%! 
Color getRandColor(int fc,int bc){//給定範圍獲得隨機顏色 
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 
//System.setProperty("java.awt.headless","true");
out.clear();
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條幹擾線，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 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，可能是因爲種子太接近，所以只能直接生成 
g.drawString(rand,13*i+6,16); 
} 

// 將認證碼存入SESSION 
request.getSession().setAttribute("rand",sRand); 
System.out.println(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();

%>