An example of a Java color Verification Code

Image Generation and verification class verifycodegenerator. Java is from http://www.blogjava.net/wuxingjia/archive/2008/04/05/410893.htmlhere!

The demo is as follows:

1. webproject:

2. source file:

1. verifycodegenerator. Java (Source: http://www.blogjava.net/wuxingjia/archive/2008/04/05/190893.html)

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. servletoutputstream;
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;
/**
* @ (#) Verifycodeservlet. Java Dec 9, 2007 8:14:14
*
* @ Author yuan
* Verification code generator. To use this class, set the name attribute of the verification code input box in the form to "verifycode"
*/
Public class verifycodegenerator {

Private Static final verifycodegenerator generator = new verifycodegenerator ();

Private final string attribute_name = "verifycode ";
// The Image Width
Private Final int width = 15;
// Image Height
Private Final int Height = 22;
// String Length
Private Final int code_length = 4;
// Random string range
Private final string rand_range = "abcdefghijklmnopqrstuvwxyz"
+ "Abcdefghijklmnopqrstuvwxyz"
+ "1234567890"
+ "@ # Quot ";

Private Final char [] chars = rand_range.tochararray ();

Private random = new random ();

Private verifycodegenerator (){
//
}

Public static verifycodegenerator getinstance (){
Return generator;
}

/**
* Generate random strings
* @ Return random string
*/
Private string getrandstring (){
Stringbuilder sb = new stringbuilder ();
For (INT I = 0; I <code_length; I ++)
SB. append (chars [random. nextint (chars. Length)]);
Return sb. tostring ();
}

/**
* Generate random colors
* @ Param ll lower limit of color value (lower limit)
* @ Param ul the upper limit of the color value (upper limit)
* @ Return: Random color object generated
*/
Private color getrandcolor (int ll, int UL ){
If (LL> 255) LL = 255;
If (LL <1) LL = 1;
If (UL> 255) UL = 255;
If (UL <1) UL = 1;
If (UL = ll) UL = LL + 1;
Int r = random. nextint (ul-LL) + ll;
Int G = random. nextint (ul-LL) + ll;
Int B = random. nextint (ul-LL) + ll;
Color color = new color (R, G, B );
Return color;
}

/**
* Generate image data of the specified string
* @ Param verifycode: the random string to be printed
* @ Return: image data generated
**/
Private bufferedimage getimage (string verifycode ){

Bufferedimage image = new bufferedimage (width * code_length, height, bufferedimage. type_int_rgb );

// Obtain the image Context
Graphics graphics = image. getgraphics ();

// Set the background color
Graphics. setcolor (getrandcolor (1, 50 ));
// Fill in the background color
Graphics. fillrect (0, 0, width * 4, height );

// Set the border color
Graphics. setcolor (new color (0,255, 0 ));
// Draw a border
For (INT I = 0; I <2; I ++)
Graphics. drawrect (I, I, width * code_length-I * 2-1, height-I * 2-1 );

// Set the random interference line color
Graphics. setcolor (getrandcolor (50,100 ));
// Generate 50 interference lines
For (INT I = 0; I <50; I ++ ){
Int X1 = random. nextint (width * code_length-4) + 2;
Int Y1 = random. nextint (height-4) + 2;
Int X2 = random. nextint (width * code_length-2-X1) + x1;
Int y2 = Y1;
Graphics. drawline (x1, Y1, X2, Y2 );
}

// Set the font
Graphics. setfont (new font ("Times New Roman", Font. Plain, 18 ));
// Draw a string
For (INT I = 0; I <this. code_length; I ++ ){
String temp = verifycode. substring (I, I + 1 );
Graphics. setcolor (getrandcolor (100,255 ));
Graphics. drawstring (temp, 13 * I + 6, 16 );
}

// The image takes effect
Graphics. Dispose ();

Return image;
}

/**
* Output the image of the Verification Code
* @ Param request the user's request object
* @ Param response the response object of the user
**/
Public void printimage (httpservletrequest request,
Httpservletresponse response ){
// Set contenttype to "image/JPEG" for the browser to recognize the image format.
Response. setcontenttype ("image/JPEG ");
// Set the page not to cache
Response. setheader ("Pragma", "No-Cache ");
Response. setheader ("cache-control", "No-Cache ");
Response. setdateheader ("expires", 2000 );

// Obtain the Random verification code
String verifycode = This. getrandstring ();
String STR = "ssss ";
For (INT I = 0; I <10; I ++)
STR = STR + STR;
// Obtain the image data of the Verification Code
Bufferedimage Bi = This. getimage (verifycode );
// Save the verification code to the session
Request. getsession (). setattribute (attribute_name, verifycode );
Try {
// Obtain the servlet output stream
Servletoutputstream outstream = response. getoutputstream ();
// Create an encoder that can encode image data as JPEG data streams
Required imageencoder encoder = required codec. createjpegencoder (outstream );
// Encode the image data
Encoder. encode (BI );
// Forcibly input the buffer content to the page
Outstream. Flush ();
// Close the output stream
Outstream. Close ();
} Catch (ioexception ex ){
Ex. printstacktrace ();
}
}

/**
* Check whether the entered verification code is correct. If the entered verification code matches the generated verification code, true is returned. Otherwise, false is returned.
* @ Param request the user's request object
* @ Return verification result
**/
Public Boolean check (httpservletrequest request ){
If (string) request. getparameter (attribute_name ))
. Inclusignorecase (string) request. getsession (). getattribute (attribute_name ))){
Request. getsession (). removeattribute (attribute_name );
Return true;
}
Return false;
}
}

2. image. Java (this servlet calls the output image)

Import java. Io. ioexception;

Import javax. servlet. servletexception;
Import javax. servlet. http. httpservlet;
Import javax. servlet. http. httpservletrequest;
Import javax. servlet. http. httpservletresponse;

Public class image extends httpservlet
{

@ Override
Protected void Service (httpservletrequest request, httpservletresponse response)
Throws servletexception, ioexception
{
Verifycodegenerator VG = verifycodegenerator. getinstance ();

VG. printimage (request, response );
}
}

3. login (this servlet processes form input)

Import java. Io. ioexception;
Import java. Io. printwriter;

Import javax. servlet. servletexception;
Import javax. servlet. http. httpservlet;
Import javax. servlet. http. httpservletrequest;
Import javax. servlet. http. httpservletresponse;

Public class login extends httpservlet
{
 
Public void doget (httpservletrequest request, httpservletresponse response)
Throws servletexception, ioexception
{
Dopost (request, response );
}

Public void dopost (httpservletrequest request, httpservletresponse response)
Throws servletexception, ioexception
{
Verifycodegenerator VG = verifycodegenerator. getinstance ();

String vcode = request. getparameter ("verifycode ");
If (null = vcode | "" = vcode. Trim ())
{
Request. setattribute ("error", "Enter the verification code! ");
Request. getrequestdispatcher ("index. jsp"). Forward (request, response );
}
Else if (true = VG. Check (request ))
Request. getrequestdispatcher ("success. jsp"). Forward (request, response );
Else
{

Request. setattribute ("error", "Incorrect verification code. Please enter it again! ");
Request. getrequestdispatcher ("index. jsp"). Forward (request, response );
}

}
}

4. Web. xml

<? XML version = "1.0" encoding = "UTF-8"?>
<Web-app version = "2.4"
Xmlns = "http://java.sun.com/xml/ns/j2ee"
Xmlns: xsi = "http://www.w3.org/2001/XMLSchema-instance"
Xsi: schemalocation = "http://java.sun.com/xml/ns/j2ee
Http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd>

<Servlet>
<Servlet-Name> login </servlet-Name>
<Servlet-class> login </servlet-class>
</Servlet>
<Servlet>
<Servlet-Name> image </servlet-Name>
<Servlet-class> image </servlet-class>
</Servlet>

<Servlet-mapping>
<Servlet-Name> login </servlet-Name>
<URL-pattern>/login </url-pattern>
</Servlet-mapping>

<Servlet-mapping>
<Servlet-Name> image </servlet-Name>
<URL-pattern>/image </url-pattern>
</Servlet-mapping>


<Welcome-file-List>
<Welcome-File> index. jsp </welcome-File>
</Welcome-file-List>
</Web-app>

5. index. jsp

<% @ Page Language = "Java" Import = "Java. util. *" pageencoding = "UTF-8" %>

<HTML>
<Head>
<SCRIPT type = "text/JavaScript">
Function refresh ()
{
Document. getelementbyid ("image"). src = 'image? Now = '+ new date ();
}
</SCRIPT>

<Title> index </title>
</Head>
<Body>
<Form action = "login">
<Table>
<Tr>
<TD> Verification Code: <input type = "text" name = "verifycode" size = "4"> <a href = "#" onclick = ""Refresh () "> <input type =" button "value =" refresh "/> </a> </TD>
</Tr>
<% IF (null! = Request. getattribute ("error") {%> <tr> <TD> <% = request. getattribute ("error") %> </TD> </tr> <%} %>
</Table>
<Input type = "Submit" value = "Submit">
</Form>
</Body>
</Html>

6. Successful success return page

<% @ Page Language = "Java" Import = "Java. util. *" pageencoding = "UTF-8" %>

<HTML>
<Head>
<Title> sucess </title>
</Head>
<Body>
Success!
</Body>
</Html>