<%@ page language="java" import="java.util.*" pageEncoding="GBK"%> 
<% 
String path = request.getContextPath(); 
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 
%> 
<%@ 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(jī)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(shè)置頁面不緩存 
response.setHeader("Pragma","No-cache"); 
response.setHeader("Cache-Control","no-cache"); 
response.setDateHeader("Expires", 0); 
// 在內(nèi)存中創(chuàng)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(jī)類 
Random random = new Random(); 
// 設(shè)定背景色 
g.setColor(getRandColor(200,250)); 
g.fillRect(0, 0, width, height); 
//設(shè)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(jī)產(chǎn)生155條干擾線，使圖象中的認(rèn)證碼不易被其它程序探測(cè)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(jī)產(chǎn)生的認(rèn)證碼(4位數(shù)字) 
String sRand=""; 
for (int i=0;i<4;i++){ 
String rand=String.valueOf(random.nextInt(10)); 
sRand+=rand; 
// 將認(rèn)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(diào)用函數(shù)出來的顏色相同，可能是因?yàn)榉N子太接近，所以只能直接生成 
g.drawString(rand,13*i+6,16); 
} 
// 將認(rèn)證碼存入SESSION 
session.setAttribute("rand",sRand); 
// 圖象生效 
g.dispose(); 
// 輸出圖象到頁面 
ImageIO.write(image, "JPEG", response.getOutputStream()); 
%> 

a.jsp------------------------------------------------------------------------------------------------------

復(fù)制代碼代碼如下:

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%> 
<% 
String path = request.getContextPath(); 
String basePath = request.getScheme() + "://" 
+ request.getServerName() + ":" + request.getServerPort() 
+ path + "/"; 
%> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<html> 
<head> 
<title>認(rèn)證碼輸入頁面</title> 
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"> 
<META HTTP-EQUIV="Pragma" CONTENT="no-cache"> 
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache"> 
<META HTTP-EQUIV="Expires" CONTENT="0"> 
</head> 
<body> 
<form method=post action="check.jsp"> 
<table> 
<tr> 
<td align=left> 
系統(tǒng)產(chǎn)生的認(rèn)證碼： 
</td> 
<td> 
<img border=0 src="image.jsp"> 
</td> 
</tr> 
<tr> 
<td align=left> 
輸入上面的認(rèn)證碼： 
</td> 
<td> 
<input type=text name=rand maxlength=4 value=""> 
</td> 
</tr> 
<tr> 
<td colspan=2 align=center> 
<input type=submit value="提交檢測(cè)"> 
</td> 
</tr> 
</table> 
</form> 
</body> 
</html>

check.jsp----------------------------------------------------------------------------------------------------------------------

復(fù)制代碼代碼如下:

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%> 
<% 
String path = request.getContextPath(); 
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 
%> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<%@ page contentType="text/html; charset=gb2312" language="java" 
import="java.sql.*" errorPage=""%> 
<html> 
<head> 
<title>認(rèn)證碼驗(yàn)證頁面</title> 
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"> 
<META HTTP-EQUIV="Pragma" CONTENT="no-cache"> 
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache"> 
<META HTTP-EQUIV="Expires" CONTENT="0"> 
</head> 
<body> 
<% 
String rand = (String) session.getAttribute("rand"); 
String input = request.getParameter("rand"); 
%> 
系統(tǒng)產(chǎn)生的認(rèn)證碼為： 
<%=rand%> 
<br> 
您輸入的認(rèn)證碼為： 
<%=input%> 
<br> 
<br> 
<% 
if (rand.equals(input)) { 
%> 
<font color=green>輸入相同，認(rèn)證成功！</font> 
<% 
} else { 
%> 
<font color=red>輸入不同，認(rèn)證失??！</font> 
<% 
} 
%> 
</body> 
</html> 