Here are some general Hibernate gotchas:
- Property names that begin or end with an underscore give Hibernate grief. It issues error messages that it cannot find properties that exist. In the case I was trying, the identifiers were all caps (other than the underscores). Perhaps it works for identifiers in normal Java case?
- When trying to use Oracle LONG columns, Hibernate would
issue the error message 'Stream has already been closed' when trying to
materialize the containing objects. This only occurs when the
containing objects have container relationships to other
objects. This error usually occurs in JDBC when ResultSet
columns are not read in left-to-right order and an attempt is made to
backtrack to a LONG column. An inspection of the Hibernate
code suggests that this is a possibility. The Hibernate
forums contain references to this problem, but no-one has posted a
solution. I tried changing the mapping so that a LONG
property appears:
- as the last property for a class -- no effect.
- in a new class mapped as a self-join to the table, with a one-to-one relationship to the original class -- this worked, but further testing is needed to verify that it works in all scenarios. Also, this mapping does not work for updates since Hibernate will think that a new row needs to be created.
- in a new component class -- no effect.
