A main limitation of detached objects (as explained on the Detached Entities manual page) is:
- Retrieval by navigation from detached objects is not supported, so only persistent fields that have been loaded before detachment should be used.
As explained on the Object DB vs EclipseLink/TopLink: on accessing lazy loaded relationships outside a transaction, after a query, from Glassfish forum thread - this JPA limitation is avoided in EclipseLink by an extension, which keep detached objects in a semi detached state (in which they are still associated with the EntityManagerFactory and enable lazy loading) - until serialization, which completes the detachment.
It seems that implementing a similar extension in ObjectDB would ease emigration of web applications from EclipseLink to ObjectDB.
ObjectDB - Fast Object Database for Java (JPA/JDO)