Re: [eclipselink-users] Small clarification needed on server session usa

[James Sutherland <jamesssss@xxxxxxxxx>]

A single EntityManager should not be used by multiple threads, this is just
logical, as an EntityManager represents a single request or transaction, it
should not be used by multiple users, a new EntityManager should be acquired
per user/thread.  An EntityManagerFactory can be used by multiple
threads/users.

The same goes for EclipseLink's native API, a ServerSession can be used by
multiple users/threads, but each user/thread should acquires its own
ClientSession.  A ClientSession and UnitOfWork should never be used by
multiple users/threads.

The ServerSession also shares the meta-data, you could also share this with
multiple DatabaseSession's but you would need to ensure you cache the
Project.


Rohit Banga-2 wrote:
> 
> One advantage of using serverSession even with a third party data source 
> can be that there will be a shared cache for all client sessions. Other 
> than that anything else?
> 
> On 3/6/2011 6:23 PM, Rohit Banga wrote:
>> Hi All     Based on the wiki we have the following facts: 1. A 
>> database session should typically be used with a two tier application.
>> 2. For three tier applications we should get a server session from 
>> EntityManagerFactory and then for each subsequent request we should 
>> acquire a client session and then if required a unit of work from the 
>> client session; subsequently releasing the client session. This allows 
>> us to reuse connections pooled by the server session. But what happens 
>> when we use a third party datasource. The connection pool is not owned 
>> by the server session. so each acquireClientSession() will request a 
>> connection from the datasource. In this case does it really matter 
>> whether we use a database session or a server session?
>> As a side note, in some of the previous posts I have read that an 
>> EntityManager is not thread safe. What about server session? Is it 
>> thread safe?
>> Thanks Rohit Banga
>>
>>
> 
> 


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