[hibernate-dev] JPA2 locking followup...

[Scott Marlow]

How should we handle the _NOWAIT variants for the three Pessimistic 
modes?  The JPA2 style is to use the "javax.persistence.lock.timeout 
(time in milliseconds, with 0 meaning no wait).

Internally, we need Hibernate core to support the three pessimistic lock 
modes (read, write, force_increment) with a JPA2 style timeout option.  
Since, we need to support JPA2 timeout per requested lock, we might want 
to support _NOWAIT via the same mechanism as we use for timeout.


On 10/30/2009 09:18 AM, Scott Marlow wrote:
> For JPA2 support, I propose that Hibernate LockMode support the
> following equivalents of JPA2 LockModeType locks:
>
>
> LockMode.OPTIMISTIC (READ)
> LockMode.OPTIMISTIC_FORCE_INCREMENT (WRITE)
> LockMode.PESSIMISTIC_READ
> LockMode.PESSIMISTIC_WRITE
> LockMode.PESSIMISTIC_FORCE_INCREMENT
>
> Hibernate already supports NONE, so that doesn't need to be added.  JPA2
> defaults to LockModeType NONE.
>
> JPA1 READ + WRITE will be supported respectively via LockMode.OPTIMISTIC
> + LockMode.OPTIMISTIC_FORCE_INCREMENT.
>
> With this change, Hibernate (native (better term?)) applications would
> be able to request JPA2 like locks.  This also means that JPA2
> applications running with the Hibernate Entity Manager, will see similar
> locking behavior as native applications.
>
> Pros:
>
> - Application developers will have a consistent set of locking options
> in their JPA2 based applications and native Hibernate applications.
>
> - This helps the application developer to prepare their native Hibernate
> application to migrate to JPA2.
>
> Cons:
>
> - This ties Hibernate core locking internals to the JPA2 specification.
> As JPA continues to evolve, Hibernate core should follow in lockstep.
> Although, that is not a hard requirement.
>
> - An alternative would be introducing low level locking primitives that
> could be combined to support JPA2 style locks.  I can explore this path
> if there is strong push back to the above proposal.
>
> Comments?
>
> Scott
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