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JPA DAO in Desktop Application [message #480317]

Fri, 14 August 2009 21:59

Marc Schlegel

Messages: 92
Registered: July 2009

Member

Hello Everyone

I've got one more question and hopefully someone can help me out here, since all
tutorials and pages I've found for JPA dont cover the DAO usage. At least not
for J2SE environments. In a Container I can just put a @EntityManager annotation
on my DAO and everything is fine but I have no clue how I should do this for my RCP.

But maybe I should start by what I already have. EclipseLink is started as
rcp-bundle and I can obtain the EntityManagerFactory for my persistence.xml. I
am also able to create EntityManger but I dont know what is the right/efficient
way for my DAOs.

Do I have to create a EntityManager for each DAO, and does it always has to be a
newly created one? Or can I reuse EntityManager-Instances (Singleton anybody ;) ).

Currently I have a Singleton-Class called JpaManager which creates the
EntityManagerFactory and this one also creates the DAOs and passes a
EntityManager Instance (which is reused). When I run my test I get an exception
regarding multiple entities in one session. I found something about a
SessionBroker but I am cufused if my approach might be totaly wrong at all (so a
SessionBroker will not help me in the end).

Could somebody clarify this a bit for me, and maybe give a best-practise tip?

Thanks in advance
-- Marc

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[Message index]

		JPA DAO in Desktop Application By: Marc Schlegel on Fri, 14 August 2009 21:59
		Re: JPA DAO in Desktop Application By: Tom Eugelink on Sat, 15 August 2009 05:59
		Re: JPA DAO in Desktop Application By: Marc Schlegel on Wed, 19 August 2009 17:35
		Re: JPA DAO in Desktop Application By: Thomas Haskes on Thu, 20 August 2009 07:34
		Re: JPA DAO in Desktop Application By: Tim Hollosy on Thu, 20 August 2009 12:05

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