Lift

It's not really about Lift widget, but I don't find better place in the wiki to share (copy/paste) I copy/paste the code I used to integrate ReCaptcha with ProtoUser (for couchdb in my case).

original article

ReCaptcha.scala

/**
 * To use ReCaptach (http://www.google.com/recaptcha) :
 * * add a project dependency
 *   <dependency>
 *     <groupId>net.tanesha.recaptcha4j</groupId>
 *     <artifactId>recaptcha4j</artifactId>
 *     <version>0.0.7</version>
 *   </dependency>   
 * * mix the trait with your MetaMegaProtoUser object and link both
 *<pre>
 *  object User extends User with XxxxMetaMegaProtoUser[User] with ReCaptcha{
 *  
 *  ...
 *  
 *  protected def reCaptchaPublicKey = ...
 *  protected def reCaptchaPrivateKey = ...
 *  
 *  // protected override def reCaptchaOptions  = (super.reCaptchaOptions merge ("theme" -> "blackglass")).asInstanceOf[JObject]      

 *  override def validateSignup(user: User): List[FieldError] = validateCaptcha() ::: super.validateSignup(user)
 *  // override localForm instead of signupXhtml if you want to use captcha for every user edition
 *  override def signupXhtml(user: User) = {
 *   (<form method="post" action={ S.uri }>
 *      <table>
 *        <tr><td colspan="2">{ S.??("sign.up") }</td></tr>
 *        { localForm(user, false) }
 *        <tr><td>&nbsp;</td><td>{ captchaXhtml() }</td></tr>
 *        <tr><td>&nbsp;</td><td><user:submit/></td></tr>
 *      </table>
 *    </form>)
 *  }
 *</pre>
 * * PublicKey and PrivateKey are provide when you register you domainName to ReCaptcha
 *   you could hardcode value, or retreive them from configuration (eg if you use Lift configuration :
 *<pre>
 *  import net.liftweb.util.Props
 *  
 *  Props.requireOrDie("reCaptcha.publicKey", "reCaptcha.privateKey")
 *  protected val reCaptchaPublicKey = Props.get("reCaptcha.publicKey").get
 *  protected val reCaptchaPrivateKey = Props.get("reCaptcha.privateKey").get
 *</pre>
 * * add localisation messages for keys (add under src/main/resources/i18n/recaptcha_xxxx.properties)
 * * modify Boot.scala
 * <pre>
 *   LiftRules.useXhtmlMimeType = false //required by ReCaptcha js lib    
 *   LiftRules.resourceNames = "recaptcha" :: LiftRules.resourceNames 
 * </pre>
 * * see http://code.google.com/apis/recaptcha/docs/java.html for troubleshooting (DNS,...), customisation (themes), ...
 * 
 * @TODO internationalize error message
 * @TODO create a "real" Lift Field for captcha
 * @author david.bernard
 */
trait ReCaptcha {
  import net.liftweb.common.{Box, Empty, Full, Failure}
  import net.liftweb.util.{FieldError, FieldIdentifier}
  import net.liftweb.http.S
  import net.tanesha.recaptcha.ReCaptchaFactory
  import net.liftweb.json.JsonAST
  import net.liftweb.json.JsonDSL._
  import net.liftweb.http.js.JsCmd
  import net.liftweb.http.js.JE.JsFunc._
  import net.liftweb.http.js.JE.JsFunc



  // add ReCaptcha  
  /**
   * Define the public key to used to connect to reCapcha service
   */
  protected def reCaptchaPublicKey : String

  /**
   * Define the private key to used to connect to reCapcha service
   */
  protected def reCaptchaPrivateKey : String

  /**
   * Define the option to configure reCaptcha widget.
   * 
   * @see http://code.google.com/apis/recaptcha/docs/customization.html to have the list possible customization
   * @return the javascript option map (as JObject)
   * @codeAsDoc
   */
  protected def reCaptchaOptions = ("theme" -> "white") ~ ("lang" -> S.containerRequest.flatMap(_.locale).map(_.getLanguage).getOrElse("en"))

  private lazy val reCaptcha = ReCaptchaFactory.newReCaptcha(reCaptchaPublicKey, reCaptchaPrivateKey, false)

  protected def captchaXhtml() = {
    import scala.xml.Unparsed
    import net.liftweb.http.js.JE
    import net.liftweb.json.JsonAST._
    import net.liftweb.json.Printer._

  val RecaptchaOptions = compact(render(reCaptchaOptions))
    <xml:group>
    <script>
        var RecaptchaOptions = {Unparsed(RecaptchaOptions)};
      </script>
      <script type="text/javascript" src={"http://api.recaptcha.net/challenge?k=" + reCaptchaPublicKey}></script>
    </xml:group>      
  }

  protected def validateCaptcha(): List[FieldError] = {
    def checkAnswer(remoteAddr : String, challenge : String, uresponse : String) : Box[String]= {
      val reCaptchaResponse = reCaptcha.checkAnswer(remoteAddr, challenge, uresponse)
      reCaptchaResponse.isValid() match {
        case true => Empty
        case false => Full(S.?("reCaptcha." + reCaptchaResponse.getErrorMessage))
      }
    }
    val res = for (
      remoteAddr <- S.containerRequest.map(_.remoteAddress);
      challenge <- S.param("recaptcha_challenge_field");
      uresponse <- S.param("recaptcha_response_field") ;
      b <- checkAnswer(remoteAddr, challenge, uresponse)
    ) yield b

    res match {
      case Failure(msg, _, _) => List(FieldError(FakeFieldIdentifier(Full("reCaptcha")), msg))
      case Full(msg) => List(FieldError(FakeFieldIdentifier(Full("reCaptcha")), msg))
      case Empty => Nil
    }
  }

  /**
   * to load a new Captcha with ajax
   * @return JsCmd
   */
  protected def reloadCaptcha() : JsCmd = JsFunc("Recaptcha.reload").cmd

  case class FakeFieldIdentifier(override val uniqueFieldId : Box[String]) extends FieldIdentifier

}

i18n/recaptcha_fr.properties

reCaptcha.invalid-site-public-key=plublic-key invalide
reCaptcha.invalid-site-private-key=private-key invalide
reCaptcha.invalid-request-cookie=cookie invalide
reCaptcha.incorrect-captcha-sol=propositon de captcha incorrecte
reCaptcha.verify-params-incorrect=paramètres de vérification incorrects
reCaptcha.recaptcha-not-reachable=server reCaptcha inaccessible

To report an error message:

<span class="lift:Msg?id=reCaptcha&errorClass=error">error</span>