Major Description
Currently Magma handles stuff in the web session correctly : it converts those values using converters, and reconverts them back when needed. This way, there is no serialization problem, and there is no JPA detached problem, because the object in the session will be re-fetched from the DB when needed in subsequent requests.
The problem arise when we save in the session in a bean that does not have a converter, and even worse if this bean itself contains field which are JPA entities. In that case, Magma will hold the bean in the session, since that's perfectly legal, but those objects will became detached.
A possible solution could be a generic bean converter, based on XML or JSON or similar to the Hibernate dehydrated representation. This should not use a premade library, unless is quite extendable, cause it should use converters recursively on the fields of the bean.
The only problem with this approach could be in URL generation. Since converter are also used during URL parsing, and they will be used in URL generation when cglib will arrive, this would mean exposing the bean internal structure to the web. This is NOT a big security concern : most of the current web technologies does this without any problem (JSON, web services .. even forms), but it could be a functional problem cause URLs are limited in size and have strict parsing limitations.