1. Foreground jsp
<% @ Page language = "java" import = "java. util. *" pageEncoding = "UTF-8" %>
<%
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>
<Base href = "<% = basePath %>">
<Title> Administrator Logon </title>
<Script type = "text/javascript" language = "javascript">
Function change (){
Var o = document. getElementById ("random ");
Var timenow = new Date (). getTime ();
O. src = "<% = path %>/server/ImageValidate? D = "+ timenow;
}
</Script>
</Head>
<Body>
/server/ImageValidate"/>
<Input type = "button" value = "change image" id = "label" onclick = "change ()"> </input>
</Body>
</Html>
2. servlet with random code in the background
Import java. AWT. color;
Import java. AWT. Font;
Import java. AWT. graphics;
Import java. AWT. image. bufferedimage;
Import java. Io. ioexception;
Import java. util. Random;
Import javax. servlet. servletexception;
Import javax. servlet. servletoutputstream;
Import javax. servlet. http. httpservlet;
Import javax. servlet. http. httpservletrequest;
Import javax. servlet. http. httpservletresponse;
Import com.sun.image.codec.jpeg. Unzip codec;
Import com.sun.image.codec.jpeg. encode imageencoder;
@ Suppresswarnings ("serial ")
Public class imagevalidate extends httpservlet {
Public imagevalidate (){
Super ();
}
Public void destroy (){
Super. destroy (); // Just puts "destroy" string in log
}
Public void doGet (HttpServletRequest request, HttpServletResponse response)
Throws ServletException, IOException {
Request. setCharacterEncoding ("GBK ");
Response. setCharacterEncoding ("GBK ");
Response. setContentType ("image/jpeg ");
Response. addHeader ("pragma", "NO-cache ");
Response. addHeader ("Cache-Control", "no-cache ");
Response. addDateHeader ("Expries", 0 );
Int width = 80, height = 30;
Response. setContentType ("text/html; charset = GBK ");
String chose = "0123456789 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ";
Char temp; // Save the randomly generated chose Element
Random rand = new Random ();
Bufferedimage image = new bufferedimage (width, height, bufferedimage. type_int_rgb );
Graphics G = image. getgraphics ();
// Fill in the background color below
G. setcolor (color. Yellow );
G. fillrect (0, 0, width, height );
// Draw a border
G. setcolor (color. Black );
Font font;
G. drawrect (0, 0, width-1, height-1 );
Stringbuffer srand = new stringbuffer ();
For (INT I = 0; I <4; I ++ ){
Temp = chose. charat (RAND. nextint (chose. Length ()));
Srand. append (temp );
Font = new font ("Arial", Font. Plain, 15 + Rand. nextint (10); // font
G. setFont (font );
G. setColor (new Color (rand. nextInt (255), 0, rand. nextInt (255); // verification code Color
G. drawString (String. valueOf (temp), 15 * I + 5, 20 + rand. nextInt (10); // location
}
Request. getSession (). setAttribute ("randomNumber", sRand. toString (); // Save the generated verification code value
// Set the font color
G. dispose ();
ServletOutputStream outStream = response. getOutputStream ();
Required imageencoder encoder = required codec. createJPEGEncoder (outStream );
Encoder. encode (image );
OutStream. close ();
}
Public void init () throws ServletException {
}
}
3. xml configuration file <servlet> <servlet-name> ImageValidate </servlet-name> <servlet-class> user. imageValidate </servlet-class> </servlet> <servlet-mapping> <servlet-name> ImageValidate </servlet-name> <url-pattern>/server/ImageValidate </url -pattern> </servlet-mapping>Start building with 50+ products and up to 12 months usage for Elastic Compute Service
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