title: TYPO3 Custom Validation not working
body: <p>My Custom Extbase Validation is not working.
  I get following Error.</p>
  
  <p>Version TYPO3 7.6.16</p>
  
  <p>I'm trying to validate the input.</p>
  
  <pre><code>Invalid validate annotation in VENDOR\ex\Domain\Model\GpSubscriber::salutation: Could not resolve class name for validator ""
  </code></pre>
  
  <p>My Model GpSubscriber.php</p>
  
  <pre><code>&lt;?php
  namespace VENDOR\ex\Domain\Model;
  
  /**
  * GpSubscriber
  */
  class GpSubscriber extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
  {
  /**
   * salutation
   *
   * @var string
   * @validate \VENDOR\ex\Domain\Validator\SalutationValidator
   */
  protected $salutation = '';
  </code></pre>
  
  <p>My Validator SalutationValidator.php</p>
  
  <pre><code>&lt;?php
  namespace VENDOR\ex\Domain\Validator;
  
  
  class SalutationValidator extends \TYPO3\CMS\Extbase\Validation\Validator\AbstractValidator {
  public function isValid($value) {
      if ($value == 'false') {
          $this-&gt;addError('error.');
          return FALSE;
      }
      return TRUE;
  }
  }
  </code></pre>
  
  <p>Where is my Problem?</p>