Hi Markus,
Just a thought on this ...
I think it might still be good to add your information to the
Persistence section of the User or Dev FAQ, whichever you think is most
appropriate:
http://wiki.glassfish.java.net/Wiki.jsp?page=GlassFishUserFAQ
http://wiki.glassfish.java.net/Wiki.jsp?page=GlassFishDeveloperFAQ
If and when the Persistence FAQ is converted to wiki format the info
could then be linked to or ported over. I'm afraid that if we wait for
the Persistence FAQ to be converted it might be awhile before this
helpful info gets out there. Anyway, just a thought. Thanks for your
work on this!
This thread also gives me the opportunity to again urge (nag? =)
everyone to contribute to the GlassFish User and Dev FAQs listed above.
So much good information is shared on the lists and it would be great
to capture that information in the FAQs.
Gail Risdal
++++++++++++++
GlassFish Documentation
Markus KARG wrote:
> Marina Vatkina schrieb:
>
>> Hi Markus,
>>
>> It's checked in under <src>/www/javaee5/persistence, but with the v3
>> work, I'm not sure how it'll work in the long run.
>>
>> There is also a wiki version with a pointer to this (old) page where
>> you can add your notes. Will it work for you?
>>
>> May be somebody would volunteer to convert the Persistence FAQ into a
>> wiki format? We can then replace the original page with the link to
>> the new wiki.
>
> I will just wait until somebody converted the Persistence FAQ into wiki
> format, to not make the same work several times... ;-)
>
> Thanks
> Markus
>
>>
>> thanks,
>> -marina
>>
>> Markus KARG wrote:
>>
>>> Alexis,
>>>
>>>> Hi Markus,
>>>>
>>>> Thanks for documenting this all.
>>>> Do you want to add this yourself to the FAQ on the Wiki?
>>>> http://wiki.glassfish.java.net/Wiki.jsp?page=GlassFishUserFAQ
>>>>
>>>> thanks,
>>>> -Alexis
>>>
>>>
>>> Okay, I am willing to contribute that to the FAQ. But I think that
>>> the best place is not the GlassFishUserFAQ but the Persistence FAQ:
>>> https://glassfish.dev.java.net/javaee5/persistence/persistence_faq.html
>>>
>>> Unfortunately I did not find out where to click to add something to
>>> that FAQ. Has anybody an idea how to gain write access to the
>>> Persistence FAQ?
>>>
>>> Thanks
>>> Markus
>>>
>>>>
>>>> On Jan 4, 2008, at 9:44, Markus KARG wrote:
>>>>
>>>>> Marina,
>>>>>
>>>>> thank you for your kind answer.
>>>>>
>>>>>> The JPA spec in the section 9.1.9 GeneratedValue Annotation says
>>>>>> about various strategies: "This specification does not define the
>>>>>> exact behavior of these strategies.". It might be a known bug in
>>>>>> TopLink, but we always advised to call em.flush() if somebody
>>>>>> needed to get a hold of the generated PK.
>>>>>
>>>>>
>>>>> You are absolutely right, I was just blind that day. ;-)
>>>>>
>>>>> In particular, I found the following in JPA 1.0 specification
>>>>> chapter "3.2.1 Persisting an Entity Instance":
>>>>>
>>>>> "A new entity instance becomes both managed and persistent by
>>>>> invoking the persist method on it or by cascading the persist
>>>>> operation. The semantics of the persist operation, applied to an
>>>>> entity X are as follows: • If X is a new entity, it becomes
>>>>> managed. The entity X will be entered into the database at or
>>>>> before transaction commit or as a result of the flush operation."
>>>>>
>>>>> Okay, that says it all: A user MUST invoke flush() or commit() to
>>>>> make the O/R mapper talk to the database server, so it is NOT a
>>>>> bug, neither of TopLink in general, nor of the particular part of
>>>>> TopLink that I wrote. That completely and unambigously answers my
>>>>> question. Once more it was helpful to ask before filing a bug
>>>>> report. :-)
>>>>>
>>>>> For all people scanning the mailing list for a solution to the same
>>>>> problem, here is the corrected code that works pretty well:
>>>>>
>>>>> em.getTransaction().begin();
>>>>> Article a1 = new Article();
>>>>> em.persist(a1);
>>>>> em.flush(); // <--- FLUSH (OR COMMIT) IS NEEDED HERE
>>>>> System.out.println(a1.getId()); // Prints: 60 // Prints: 0 WITHOUT
>>>>> flush() or commit()
>>>>> Article a2 = em.find(Article.class, 60);
>>>>> System.out.println(a2.getId()); // Prints: 60
>>>>> em.getTransaction().commit();
>>>>>
>>>>> Maybe someone likes to add this snippet tho the user's FAQ. :-)
>>>>>
>>>>> Thanks for pointing me in the right direction!
>>>>>
>>>>> Have Fun
>>>>> Markus
>>>>>
>>>>>>
>>>>>> Regards,
>>>>>> -marina
>>>>>>
>>>>>> Markus KARG wrote:
>>>>>>
>>>>>>> Hi all,
>>>>>>>
>>>>>>> as you know, I am the author of the Sybase support in TopLink
>>>>>>> Essentials. :-)
>>>>>>>
>>>>>>> I just tried a short code snipped and noticed a strange
>>>>>>> behaviour. Since I do not know whether that is wanted by JPA
>>>>>>> spec, or a bug of TopLink, or a bug of my own code, I want to
>>>>>>> discuss with you prior to filing a bug report.
>>>>>>>
>>>>>>> See the following code snippet:
>>>>>>>
>>>>>>> em.getTransaction().begin();
>>>>>>> Article a1 = new Article();
>>>>>>> em.persist(a1);
>>>>>>> System.out.println(a1.getId()); // Prints: 0
>>>>>>> Article a2 = em.find(Article.class, 60);
>>>>>>> System.out.println(a2.getId()); // Prints: 60
>>>>>>> em.getTransaction().commit();
>>>>>>>
>>>>>>> "Article" is an entity that is using IDENTITY strategy for
>>>>>>> generating its primary key:
>>>>>>>
>>>>>>> @Id
>>>>>>> @GeneratedValue(strategy = GenerationType.IDENTITY)
>>>>>>> private int id;
>>>>>>>
>>>>>>> The database wrapper used, obviously, is the one I wrote. ;-)
>>>>>>>
>>>>>>> As you can see, when asking for the generated ID directly after
>>>>>>> em.persist(a1), it returns the wrong value of 0. In fact, it
>>>>>>> certainly shall tell the actually generated value of 60, since it
>>>>>>> is impossible to know that value -- and such it is impossible to
>>>>>>> ask for that PK explicitely as I have done it in the em.find()
>>>>>>> line. But knowing the PK might be critical to some use cases. In
>>>>>>> fact, my Sybase wrapper included in TopLink so far has code that
>>>>>>> reads back the created value -- but it seems that value gets lost
>>>>>>> "somewhere". I know that somebody changed my code recently to
>>>>>>> support IDENTITY and SEQUENCE strategy at the same time. Maybe he
>>>>>>> broke it?
>>>>>>>
>>>>>>> So my question is: IS THAT A BUG?
>>>>>>>
>>>>>>> And if it is: Is that a bug of my Sybase wrapper, or a bug of
>>>>>>> TopLink?
>>>>>>>
>>>>>>> Thanks
>>>>>>> Markus
>>>>>>>
>>>>>>
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>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> http://www.xing.com/go/invita/58469
>>>>>
>>>>>
>>>>
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>>>>
>>>
>>>
>>
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>
>