<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Login Page</title>
<script language="javascript">
function loadImage()
{
document.getElementById("randImage").src="image.jsp?"+Math.random();
}
</script>
</head>
<body>
<form action="validate.jsp" method="post">
<table cellspacing="1" cellpadding="3" border="0">
<tr>
<td colspan="2">Please enter your verification code</td>
</tr>
<tr>
<td><input type="text" name="vcode"/></td>
<td><img src="image.jsp" id="randImage"/></td>
</tr>
<tr>
<td colspan="2"><a href="javascript:loadImage()">Change an image</a></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="Submit"/></td>
</tr>
</table>
</form>
</body>
</html>
<%@ page language="java"%>
<%@ page import="java.awt.*,java.awt.image.*,java.util.*" %>
<%@ page import="java.io.OutputStream,javax.imageio.*"%>
<%!
Color getRandColor(int fc,int bc){
if(fc>255){
fc=255;
}
if(bc>255){
bc=255;
}
Random random=new Random();
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);
}
%>
<%
//本地无缓存,每次自动刷新
response.addHeader("pragma", "No-cashe");
response.addHeader("cashe-control","no-cashe");
response.setDateHeader("expires",0);
int width=60,height=20;
BufferedImage bimg=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics g=bimg.getGraphics();
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
g.setColor(getRandColor(160,200));
Random rand=new Random();
for(int i=0;i<200;i++){
int x=rand.nextInt(width);
int y=rand.nextInt(height);
int w=rand.nextInt(12);
int h=rand.nextInt(12);
g.drawLine(x, y, x+w, y+h);
}
String srand="";
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
for(int i=0;i<4;i++){
String num=String.valueOf(rand.nextInt(10));
srand+=num;
g.setColor(new Color(20+rand.nextInt(110),20+rand.nextInt(110),20+rand.nextInt(110)));
g.drawString(num, 13*i+6, 16);
}
session.setAttribute("srand", srand);
OutputStream os=response.getOutputStream();
ImageIO.write(bimg, "jpeg", os);
os.flush();
os.close();
os=null;
g.dispose();
//这两句非常重要，如果没有会报错
out.clear();
out=pageContext.popBody();
%>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Validate Page</title>
</head>
<body>
<%
String str=(String)session.getAttribute("srand");
String incode=request.getParameter("vcode");
if(str.equals(incode)){
out.println("<font size=\"+3\" color=\"#000\">The verification is right!</font><br/>");
out.println("<font size=\"+4\" color=\"#FF0000\">Welcone to the page!</font><br/><hr/>");
}else{
out.println("<font size=\"+4\" color=\"#FF0000\">"
+"Sorry the verification code is not right</font></br><hr>");
}
out.println("<br/><a href=\"login.jsp\">Back to the login page</a>");
%>
</body>
</html>
原文地址：http://blog.csdn.net/cjc211322/article/details/41719247
