title: JDO app engine: exception thrown when trying to persist class's List member
body: <p>I am running the following JDO code on an app engine server.</p>
  
  <p>I am getting the following error message:</p>
  
  <p>org.datanucleus.jdo.exceptions.ClassNotPersistenceCapableException: The class "The class "java.util.ArrayList" is not persistable. This means that it either hasnt been enhanced, or that the enhanced version of the file is not in the CLASSPATH (or is hidden by an unenhanced version), or the Meta-Data/annotations for the class are not found." is not persistable. This means that it either hasnt been enhanced, or that the enhanced version of the file is not in the CLASSPATH (or is hidden by an unenhanced version), or the Meta-Data for the class is not found.</p>
  
  <p>Here is my class:</p>
  
  <pre><code>@PersistenceCapable(detachable="true")
  class Store {
  
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    private Key key;
  
    @Persistent
    @Element(dependent = "true")
    private List&lt;User&gt; users;
  
    List&lt;User&gt; getUsers() {
      return users;
    }
  
  }
  </code></pre>
  
  <p>When I run</p>
  
  <pre><code>pm.makePersistent(store.getUsers());
  </code></pre>
  
  <p>I get the above exception. Any idea as to why this is happening?
  I thought the documentation stated I could have a List&lt;> as a persistent
  element and that it would turn into a multivalued property.</p>
  
  <p>Thanks,</p>
  
  <p>John Goche</p>