[seam-dev] [seam-persistence] ManagedPersistenceContextExtension

[Stuart Douglas]

On 11/07/2011, at 4:07 AM, Mark Struberg wrote:

> Hi folks!
> 
> While reviewing an OWB bug report, 2 questions came up:
> 
> a.) EnvironmentUtils#isEEEnvironment() relies on the absence of 'javax.ejb.Stateless' to decide if a PersitenceUnit gets injected or if you need to do it yourself. I think this is an unrelieable assumption. E.g. there are a few Extensions which emulate Stateless Session beans via a CDI Extension by morphing them into @ApplicationScoped.

This is not ideal, but I don't think there is really any portable way to detect if the environment is an EE environment or not. I was originally planning to add a method for configuring this, but it appears I did not get around to it. 

> 
> b.) in ManagedPersistenceContextExtension#registerManagedPersistenceContext you register the bean for the EntityManager as passivationCapable. This is never _never_ NEVER true. The EntityManager is not Serializable! There is imo no way to have an EntityManager in a bean scoped other than @RequestScoped or shorter (e.g. @TransactionalScoped). Any other trick is not working in a portable way. This is mainly caused by JPA still supporting pessimistic locking (_real_ locks in the database) as first class citizens. 
> 

Without this it is not possible to have a conversation scoped entity manager. The hibernate EntityManager is in fact Serializable. Locks should not be a problem as long as you do not attempt to serialise the EM in the middle of a transaction.

Stuart


> But I'd be happy if anyone could enlighten me and tell us how it works ;) 
> 
> LieGrue,
> strub
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