title: Exclude Entity fields from updating process in forms Symfony2
body: <p>I'm in a situation where the edit form of an Entity is a little bit different than the create form. I don't show some fields, because I don't want them to be editable.</p>
  
  <p>But when I save this form, all not included fields are set to null and are saved, but I want to exclude those fields from the whole updating process.</p>
  
  <p>How can I achieve this?</p>