1. Establishment of IMAGE.JSP documents, as follows:
<%@ page contenttype= "Image/jpeg"
Import= "Java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%! 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);
}%>
<%
Out.clear ()//This sentence for the resin server, if it is tomacat can not this sentence
Response.setheader ("Pragma", "No-cache");
Response.setheader ("Cache-control", "No-cache");
Response.setdateheader ("Expires", 0);
int width =, 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.plain, 18));
G.setcolor (Getrandcolor (160, 200));
for (int i = 0; i < i++) {
int x = random.nextint (width);
int y = random.nextint (height);
int xl = Random.nextint (10);
int yl = Random.nextint (10);
G.drawline (x, y, X + xl, y + yl);
}
Char c[] = new char[62];
for (int i = 123, j = 0; I < i++, j + +) {
C[J] = (char) i;
}
for (int o = o++, p =; o <; p++) {
C[P] = (char) o;
}
for (int m =, n = m < m++, n++) {
C[n] = (char) m;
}
String SRand = "";
for (int i = 0; i < 4; i++) {
int x = Random.nextint (62);
String rand = string.valueof (c[x]);
SRand + rand;
G.setcolor (New Color (+ random.nextint), + random
. Nextint, + random.nextint (110));
g.DrawString (Rand, * i + 6, 16);
}
Save authentication Code in session
Session.setattribute ("Rand", SRand);
System.out.println (SRand);
G.dispose ();
Imageio.setusecache (TRUE);
Imageio.write (Image, "JPEG", Response.getoutputstream ());
%>
2. Establish the verification page validate.jsp, as follows
<%@ page language= "java" contenttype= "text/html; charset=gb2312 "
pageencoding= "GB2312"%>
<! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" "HTTP://WWW.W3.ORG/TR/HTML4/LOOSE.DTD" >
<meta http-equiv= "Content-type" content= "text/html; charset=gb2312 ">
<title> Validation </title>
<body>
<%! String rand = NULL;
String input = null;%>
<%
Rand = (String) session.getattribute ("Rand");
input = Request.getparameter ("Yanzhengma");
%>
The Verification code is:
<%=rand%>
Your input is:
<%=input%>
<%
if (rand.equals (input)) {
%>
<font Color=green> entered the same, authentication succeeded. </font>
<%
} else {
%>
<font color=red> input is different, authentication failed. </font>
<%
}
%>
</body>
3. Set up the login page login.jsp as follows
<%@ page language= "java" import= "java.sql.*" errorpage= ""%>
<%
Request.setcharacterencoding ("GB2312");
%>
<% @page pageencoding= "GB2312"%>
<meta http-equiv= "Content-type" content= "text/html; charset=gb2312 ">
<title> User Login </title>
<script language= "JavaScript" >
function LoadImage () {
document.getElementById ("Randimage"). src = "image.jsp?" +math.random ();
}
</script>
<body>
<table width= "256" border= "0" cellpadding= "0" cellspacing= "0" >
<!--dwlayouttable-->
<form action= "validate.jsp" method= "post" name= "LoginForm" >
<tr>
<TD width= "118" height= "valign=" Middle "center" align=
Type= "text" name= "Yanzhengma" size= "></td>"
<TD width= "138" valign= "Middle" align= "center" >Name= "Randimage" id= "Randimage" src= "image.jsp" width= "60"
height= "border=" "1" align= "Absmiddle" ></td>
</tr>
<tr>
<TD height= "colspan=" "2" align= "center" valign= "Middle" ><a
Href= "Javascript:loadimage ();" ><font class=pt95> don't count me </font></a></td>
</tr>
<tr>
<TD height= "colspan=" "2" align= "center" valign= "Middle" ><input
Type= "Submit" name= "Login" value= "submitted" ></td>
</tr>
</form>
</table>
</body>
