title: morphia query based on single field of deeply nested object
body: <p>I want to retrieve an object, based on an id (or other single field) of an object that is nested 2 levels from the object that I want to retrieve. An example to demonstrate:</p>
  
  <p>I want to find all blog posts that have been commented on by a particular user.</p>
  
  <pre><code>Blog
    List&lt;Comment&gt;
      ignoredField1
      ignoredField2
      User
        id
        name
        ignoredField3
  </code></pre>
  
  <p>Comments and Users are @Referenced by their parent objects. </p>
  
  <p>After reading this post
  <a href="http://groups.google.com/group/morphia/browse_thread/thread/57090ef1bd2f3e74?pli=1" rel="noreferrer">http://groups.google.com/group/morphia/browse_thread/thread/57090ef1bd2f3e74?pli=1</a></p>
  
  <p>I understand how i would find blogs with comments where ignoredField1/2 has a particular value, but i want to navigate further than that. </p>
  
  <p>I have tried the following but because all Comment fields are compared, there is no match</p>
  
  <pre><code>q.field("comments").hasThisElement(new Comment(new User("name")));
  </code></pre>