title: dynamic default property grails
body: <p>i tried to set a default value in a domain-class. i tried this but don't work</p>
  
  <pre><code>class myDomainClass{
      int idUser = (${session.user.id}!= null)?${session.user.id}:0; 
  }
  </code></pre>
  
  <p>how can i do it?</p>