我需要List<myClass>在一个jsp中迭代一个。这是我获取列表的方式：

（当我发表评论时，页面加载正常）。

 <%
      List<myClass> pjList = null;
      StringBuffer ejbQuery = new StringBuffer();

      EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPersistence");
      EntityManager em = emf.createEntityManager();

      ejbQuery.append("SELECT e ");
      ejbQuery.append("FROM myClass e ");
      pjList = em.createQuery(ejbQuery.toString()).getResultList();


for(myClass pj : pjList)
{
    %>
    <br />
    <%= pj.getSomeField()%>
    <br />
    <%
}
%>

这是我在Google Appengine中运行它时遇到的错误。在本地运行良好。

Uncaught exception from servlet
java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.String
 at org.datanucleus.store.appengine.DatastoreFieldManager.fetchStringField(DatastoreFieldManager.java:188)
 at org.datanucleus.state.AbstractStateManager.replacingStringField(AbstractStateManager.java:1180)
 at ar.edu.kennedy.proveedores.entities.ProEnteEy.jdoReplaceField(ProEnteEy.java)
 at ar.edu.kennedy.proveedores.entities.ProPersonaJuridicaEy.jdoReplaceField(ProPersonaJuridicaEy.java)
 at ar.edu.kennedy.proveedores.entities.ProEnteEy.jdoReplaceFields(ProEnteEy.java)
 at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:2772)
 at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:2791)
 at org.datanucleus.store.appengine.DatastorePersistenceHandler.fetchObject(DatastorePersistenceHandler.java:443)
 at org.datanucleus.store.appengine.query.DatastoreQuery.entityToPojo(DatastoreQuery.java:433)
 at org.datanucleus.store.appengine.query.DatastoreQuery.entityToPojo(DatastoreQuery.java:391)
 at org.datanucleus.store.appengine.query.DatastoreQuery.access$800(DatastoreQuery.java:97)
 at org.datanucleus.store.appengine.query.DatastoreQuery$5.apply(DatastoreQuery.java:515)
 at org.datanucleus.store.appengine.query.DatastoreQuery$5.apply(DatastoreQuery.java:507)
 at org.datanucleus.store.appengine.query.StreamingQueryResult.resolveNext(StreamingQueryResult.java:137)
 at org.datanucleus.store.appengine.query.StreamingQueryResult$1.computeNext(StreamingQueryResult.java:163)
 at org.datanucleus.store.appengine.query.AbstractIterator.tryToComputeNext(AbstractIterator.java:132)
 at org.datanucleus.store.appengine.query.AbstractIterator.hasNext(AbstractIterator.java:127)
 at org.datanucleus.store.appengine.query.StreamingQueryResult$AbstractListIterator.hasNext(StreamingQueryResult.java:229)
 at org.apache.jsp.busqueda_jsp._jspService(busqueda_jsp.java:138)

如果我使用ListIterator并调用hasNext（），则会出现相同的错误。帮助我了解发生了什么，如何解决？