@Entity
    @NamedQueries({
         @NamedQuery(name = "invoice.all", query = "SELECT i FROM Invoice i")})


    @NamedEntityGraph(name = "graph.invoice",
                attributeNodes = {@NamedAttributeNode("invoiceNum")})

    @Table(name = "INVOICE")
    public class Invoice implements Serializable {
            private int id;
            private String bizonylatSzam;
            ...
        }

EntityManager em = getEntityManagerFactory().createEntityManager();
EntityGraph eg = em.createEntityGraph("graph.invoice");
List<Invoice> invoiceList =  em.createNamedQuery("invoice.all").setHint("javax.persistence.fetchgraph", eg).getResultList();

org.eclipse.persistence.exceptions.QueryException Exception Description: You must define a fetch group manager at descriptor (Invoice) in order to set a fetch group on the query (invoice.all)

 WARN  [MyDaO] (default task-24) null: javax.persistence.PersistenceException: Exception [EclipseLink-6112] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.QueryException
Exception Description: Fetch group cannot be set on report query.
Query: ReportQuery(referenceClass=MyEntityA )
FetchGroup(null){fieldA=> {class MyEntityB=FetchGroup(fieldA){}}, fieldB, fieldC=> {class MyEntityC=FetchGroup(fieldC){}}, fieldD=> {class MyEntityD=FetchGroup(fieldD){}}, fieldE, fieldF, fieldG, fieldH, fieldI}