title: is it possible to get the Entity object before objectify saves it (and fill some other data)
body: <p>I have some personal data structure mixed with "standard fields". I would like to avoid the manual work on simple fields (with datastore native API):</p>
  
  <pre><code>toPersist.setProperty("field1", value1);
  toPersist.setUnindexedProperty("field2", value2);
  </code></pre>
  
  <p>but I still want to get the prefilled Entity instance <code>toPersist</code> so I can add my own <code>@Ignore</code> fields my self</p>
  
  <p>For example:</p>
  
  <pre><code>Entity filled = OfyService.ofy().save().entity(this).fill();
  filled.setProperty("mySpecialField", jsonValue);
  //...
  // I want to save my entities alone
  datastore.put( filled );
  </code></pre>
  
  <p>reversely I'd like to get the Entity object representing each entry in a <code>load()</code> call.</p>
  
  <p>Is this possible? or do I have to dive into Objectify code to hack it?</p>
  
  <p>thanks for your answers</p>