The following sections outline the limitations OpenJPA places on specific mapping strategies.
Table-per-class inheritance mapping has the following limitations:
You cannot traverse polymorphic relations to non-leaf classes in a table-per-class inheritance hierarchy in queries.
You cannot map a one-sided polymorphic relation to a non-leaf class in a table-per-class inheritance hierarchy using an inverse foreign key.
You cannot use an order column in a polymorphic relation to a non-leaf class in a table-per-class inheritance hierarchy mapped with an inverse foreign key.
Table-per-class hierarchies impose limitations on eager fetching. See Section 7.2, “ Eager Fetching Considerations and Limitations ”.
Non-polymorphic relations do not suffer from these limitations. You can declare a non-polymorphic relation using the extensions described in Section 9.2.2, “ Nonpolymorphic ”.