title: PrimeFaces DataTable InCell editing - non-trivial validation
body: <p>I want to use both <strong>InCell</strong> editing in <strong>DataTable</strong> and the validation. I know that the trivial validations can be solved with f:validator, but what with non-trivial names?</p>
  
  <p>I must, let's say, assure that the 'name' property is unique in the table. So, before accepting the edit, I should check if the name is changed and if it is used by another element. If so, the edit must be <strong>refused</strong>.</p>
  
  <p>How to achieve it? The eventListener would be only notified that the edit was accepted, as I have understood, so theoretically I could react and revert it, but I would prefer to refuse the edit when user clicks the 'accept' icon.</p>