[hibernate-dev] [OGM] Transactions in Neo4j datastore

[Gunnar Morling]

2013/10/25 Davide D'Alto <daltodavide at gmail.com>

> The isNeo4j() is just a trick so that the user does not have to set a
> property. I'm also not totally happy about it
>

Ok, I see. Good we agree :) I've created OGM-370 for this.

>
>
> > Neo4j seems to allow for this via the TransactionManagerProvider SPI.
> Unfortunately one isn't in control of instantiating such providers, though.
> So one would have to do some hackery using a static variable, ThreadLocal
> or similar to pass in the JtaPlatform. WDYT, would that make sense?
>
> This was actually the original intention. I've tried to hack a bit in the
> interface but in the end there was always something not working (at some
> point I was able to inject the JtaPlatform in Neo4j but I don't remember
> how to do it). In the end this one was the easiest one to implement.
>

I'm happy if you want to explore this solution but I think we should talk
> with the Neo4j guys first to see if it is possible to add an option to pass
> an already created object.
> It seems easier and it doesn't requires hacks.
>

Yes, that'd be nice. I've just asked this question on your PR.

On Fri, Oct 25, 2013 at 12:40 PM, Gunnar Morling <gunnar at hibernate.org>wrote:
>
>> Hi Davide,
>>
>> I'm wondering why instead of creating Neo4jJtaPlatform we don't provide
>> the TransactionManager as retrieved from ORM's JtaPlatform to Neo4j (as we
>> e.g. do for ISPN)? I find the isNeo4j() code in ogm-core a bit
>> discomforting.
>>
>> Neo4j seems to allow for this via the TransactionManagerProvider SPI.
>> Unfortunately one isn't in control of instantiating such providers, though.
>> So one would have to do some hackery using a static variable, ThreadLocal
>> or similar to pass in the JtaPlatform. WDYT, would that make sense?
>>
>> --Gunnar
>>
>>
>>
>>
>> 2013/3/13 Davide D'Alto <daltodavide at gmail.com>
>>
>>> Well...I don't have alternative at the moment.
>>>
>>> I think we could keep it as it is now and wait for some feedback from
>>> the users.
>>>
>>> On Mon, Mar 4, 2013 at 1:17 PM, Emmanuel Bernard <emmanuel at hibernate.org>
>>> wrote:
>>> > Do you have an alternative in mind?
>>> >
>>> > My understanding is that if you write a Neo4J JtaPlatform, then the
>>> > transaction will be started:
>>> >
>>> > - if the transaction is manually started by the wrapping code
>>> > - if someone uses Session.beginTransaction() or
>>> >   EntityManager.getTransaction().begin()
>>> >
>>> > You wanted the Neo4J transaction to be started if @Transactional is
>>> > added to a CDI bean? I'd say that's the job of the Neo4J team to amke
>>> > sure that one works, no?
>>> >
>>> > If we can find a better solution that would be nice but I'm not sure I
>>> > understand the problem :)
>>> >
>>> > Emmanuel
>>> >
>>> > On Mon 2013-02-25 15:08, Davide D'Alto wrote:
>>> >> Hi,
>>> >> I'm working at the integration between OGM and Neo4j.
>>> >>
>>> >> Neo4j is fully transactional and it requires to open a transaction
>>> >> before the execution of any operation on the DB.
>>> >> To integrate this mechanism with OGM I've created the class
>>> >> Neo4jJtaPlatform.java[1] that extends AbstractJtaPlatform and it's
>>> >> registered using the configuration parameter
>>> >> hibernate.transaction.jta.platform
>>> >> If I'm correct, while this solution is working, it requires the
>>> >> application to manage transactions using the Neo4j transaction
>>> >> manager. Are there alternatives to this approach?
>>> >>
>>> >> The related pull request can be found at
>>> >> https://github.com/hibernate/hibernate-ogm/pull/132
>>> >>
>>> >> Thanks,
>>> >> Davide
>>> >>
>>> >> [1]
>>> https://github.com/DavideD/hibernate-ogm/blob/2b6588998673bce8a9ccd973f693d7fe091e8c9c/hibernate-ogm-neo4j/src/main/java/org/hibernate/ogm/dialect/neo4j/Neo4jJtaPlatform.java
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>>
>>
>