Use the Open Source component jcaptcha for JSP color Verification Code

Use the Open Source component jcaptcha for JSP color Verification Code Key Words: JSP Verification Code jcaptcha

For more information, see

Install

Add jcaptcha-all.jar (provided inBin-distribution) And ehcache. Jar (not provided seeEhcache site) To your application class path, ie in you WEB-INF/lib folder.

A jcaptcha service for the instance. Note that the service must be in singleton mode. ImportCom. Octo. CAPTCHA. Service. image. imagecaptchaservice;
ImportCom. Octo. CAPTCHA. Service. image. defamanagmanageableimagecaptchaservice;

Public   Class Captchaservicesingleton {

Private   Static Imagecaptchaservice instance =   New Defaultmanageableimagecaptchaservice ();

Public   Static Imagecaptchaservice getinstance (){
Return Instance;
}
}

Note: The above is a default implementation, and the following are more implementations.

• Simplelistsoundcaptchaengine // You can also use the sound. It's amazing.
• Spellersoundcaptchaengine
• Spellersoundcaptchaengine
• Defaultgimpyenginecaptcha
• Bafflelistgimpyenginecaptcha
• Basiclistgimpyenginecaptcha
• Deformedbafflelistgimpyenginecaptcha
• Doublerandomlistgimpyenginecaptcha
• Simplelistimagecaptchaenginecaptcha
• Simplefisheyeenginecaptcha

For details, refer to official instructions.

Compile a servlet for generating images

ImportCom. Octo. CAPTCHA. Service. captchaserviceexception;
ImportCom.sun.image.codec.jpeg. Unzip codec;
ImportCom.sun.image.codec.jpeg. Specify imageencoder;

Import Javax. servlet. servletconfig;
Import Javax. servlet. servletexception;
Import Javax. servlet. servletoutputstream;
Import Javax. servlet. http. httpservlet;
Import Javax. servlet. http. httpservletrequest;
Import Javax. servlet. http. httpservletresponse;
Import Java. AWT. image. bufferedimage;
Import Java. Io. bytearrayoutputstream;
Import Java. Io. ioexception;

Public ClassImagecaptchaservletExtendsHttpservlet {

Public VoidInit (servletconfig)ThrowsServletexception {

Super. INIT (servletconfig );

}

Protected   Void Doget (httpservletrequest, httpservletresponse) Throws Servletexception, ioexception {

Byte [] Captchachallengeasjpeg =   Null ;
// The output stream to render the CAPTCHA image as JPEG
Bytearrayoutputstream extends outputstream =   New Bytearrayoutputstream ();
Try {
// Get the session ID that will identify the generated CAPTCHA.
// The same ID must be used to validate the response, the session ID is a good candidate!
String captchaid = Httpservletrequest. getsession (). GETID ();
// Call the imagecaptchaservice getchallenge Method
Bufferedimage challenge =
Captchaservicesingleton. getinstance (). getimagechallengeforid (captchaid,
Httpservletrequest. getlocale ());

// A jpeg Encoder
Incluimageencoder incluencoder =
Using codec. createjpegencoder (using outputstream );
Incluencoder. encode (Challenge );
} Catch (Illegalargumentexception e ){
Httpservletresponse. senderror (httpservletresponse. SC _not_found );
Return ;
} Catch (Captchaserviceexception e ){
Httpservletresponse. senderror (httpservletresponse. SC _internal_server_error );
Return ;
}

Captchachallengeasjpeg=Using outputstream. tobytearray ();

// Flush it in the response
Httpservletresponse. setheader ( " Cache-control " , " No-store " );
Httpservletresponse. setheader ( " Pragma " , " No-Cache " );
Httpservletresponse. setdateheader ( " Expires " , 0 );
Httpservletresponse. setcontenttype ( " Image/JPEG " );
Servletoutputstream responseoutputstream =
Httpservletresponse. getoutputstream ();
Responseoutputstream. Write (captchachallengeasjpeg );
Responseoutputstream. Flush ();
Responseoutputstream. Close ();
}
}

Modify the Web. xml configuration file for Servlet < Servlet >
< Servlet-name > Jcaptcha </ Servlet-name >
< Servlet-class > Imagecaptchaservlet </ Servlet-class >
< Load-on-startup > 0 </ Load-on-startup >
</ Servlet >

< Servlet-Mapping >
< Servlet-name > Jcaptcha </ Servlet-name >
< URL-Pattern > /Jcaptcha </ URL-Pattern >
</ Servlet-Mapping >

Compile your client presentation <IMGSRC= "Jcaptcha">
<InputType= 'Text'Name= 'J _ captcha_response'Value=''>

The above src = "jcaptcha" indicates that the above servlet is called, and the text contains the verification code entered by the user.

Background logic verification Boolean isresponsecorrect = Boolean. False;
// Remenber that we need an ID to validate!
String captchaid = Httpservletrequest. getsession (). GETID ();
// Retrieve the response
String response = Httpservletrequest. getparameter ( " J_captcha_response " );
// Call the service method
Try {
Isresponsecorrect = Captchaservicesingleton. getinstance (). validateresponseforid (captchaid,
Response );
} Catch (Captchaserviceexception e ){
// Shocould not happen, may be thrown if the ID is not valid
}

OK. You are done.