Re: [eclipselink-users] multiple EntityManagers in one process

["Andrei Ilitchev" <andrei.ilitchev@xxxxxxxxxx>]

 

----- Original Message -----

From: "David Parker" <dap@xxxxxxxxxxxxxxxxxxxx>

To: "EclipseLink User Discussions" <eclipselink-users@xxxxxxxxxxx>

Sent: Thursday, May 21, 2009 10:31 AM

Subject: Re: [eclipselink-users] multiple EntityManagers in one process

> OK, after asking that question, I found the following thread:
> http://dev.eclipse.org/mhonarc/lists/eclipselink-users/msg02625.html
>
> So this is my understanding:
>
> A singleton ServerSession is associated with a named persistence unit. 
> Any EntityManagerFactory/EntityManager created under that PU name will 
> share the same ServerSession.
>
> Is this correct?

Yes.

>
> I need to create a schema associated with my existing PU in the new 
> database. Is it possible to create a new PersistenceUnit name on the 
> fly?
>

If you don't need the two ServerSessions connected simultaneously you can re-use the same ServerSession:

 

Map prop1 = new HashMap();

// populate prop1

EntityManagerFactory factory1 = persistence.createEntityManagerFactory("MyPU", prop1);

...

factory1.close();

Map prop2 = new HashMap();

// populate prop2

EntityManagerFactory factory2 = persistence.createEntityManagerFactory("MyPU", prop2);

...

 

If you need two ServerSessions to co-exist, try using "eclipselink.session-name" property:

Map prop1 = new HashMap();

// populate prop1

prop1.put("eclipselink.session-name", "session1");

EntityManagerFactory factory1 = persistence.createEntityManagerFactory("MyPU", prop1);

Map prop2 = new HashMap();

// populate prop2

prop2.put("eclipselink.session-name", "session2");

EntityManagerFactory factory2 = persistence.createEntityManagerFactory("MyPU", prop2);

 

I believe that should work but couldn't find a test and haven't tried it myself.

 

Thanks,

 

Andrei

> On May 20, 2009, at 4:08 PM, David Parker wrote:
>
>> I am trying to build a schema migration functionality that requires 
>> separate connections to different databases.
>>
>> What is happening is that the first entitymanagerfactory is 
>> initialized, connected to its database. Then I create another 
>> entitymanagerfactory with a different set of connection properties, 
>> using
>>
>>    public static String JPA_DRIVER_PROP = "eclipselink.jdbc.driver";
>>    public static String JPA_URL_PROP = "eclipselink.jdbc.url";
>>    public static String JPA_USER_PROP = "eclipselink.jdbc.user";
>>    public static String JPA_PASSWORD_PROP = 
>> "eclipselink.jdbc.password";
>>
>> property names. Despite creating a "new" EntityManagerFactory object 
>> with a different set of properties, it still connects to the 
>> original database, i.e., it has the same connection information 
>> internally as the original entitymanagerfactory. I notice that it 
>> shares the same DatabaseAccessor object.
>>
>> I'm clearly not understanding how this is supposed to work. What is 
>> the correct way to go about maintaining connections to separate 
>> databases?
>>
>> Thanks.
>>
>> =============================================
>> David Parker
>> dap@xxxxxxxxxxxxxxxxxxxx
>>
>>
>>
>>
>> _______________________________________________
>> eclipselink-users mailing list
>> eclipselink-users@xxxxxxxxxxx
>> https://dev.eclipse.org/mailman/listinfo/eclipselink-users
>>
>
> =============================================
> David Parker
> dap@xxxxxxxxxxxxxxxxxxxx
>
>
>
>
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