Hi, Am Donnerstag, den 10.06.2010, 19:56 +0200 schrieb Norman Maurer: > After thinking a bit more about it, could it be that the two tables > are used for mapping ? I think that would make sense because we have a > many relation here.. > > So one for mapping Message and Properties and one for Message and Header. That's true. However, we don't have Many-to-many mappings here, but one to many (as defined in AbstractJPAMessage). So these tables are basically superfluous and causing (little) performance loss. The reason they are created by OpenJPA is that the mappings are unidirectional.
Although we don't need a "message" field in Headers and Properties I think we should introduce it and thus allow for One-To-Many without mapping table. I already tried doing that, adding @JoinColum and "mappedBy" according to the specification: http://java.sun.com/javaee/5/docs/api/javax/persistence/OneToMany.html However, when mappedBy="message" is added to the AbstractJPAMessage then OpenJPA hangs without any error output (despite <property name="openjpa.Log" value="SQL=TRACE"/>) and the tables won't get created. If put into JPAMessage (overriding the field) the tables get created as usual simply with the addition of a join column (in Header). I guess it has to do with the inheritance. Any idea? Otherwise I'd ask on some OpenJPA mailing list. Besides that there is a proprietary solution for OpenJPA: @OneToMany(cascade = CascadeType.ALL, fetch=FetchType.LAZY) @ElementJoinColumn(name="message_id", referencedColumnName="id") private List<JPAHeader> headers; This fixes the issue but is non-standard. Other framworks like jpox also have such options if I don't err. Tim --------------------------------------------------------------------- To unsubscribe, e-mail: server-dev-unsubscr...@james.apache.org For additional commands, e-mail: server-dev-h...@james.apache.org
