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Re: JPA and extra fields

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On 13/08/2015 19:12, Cecil Westerhof wrote:
> I am new to JPA. I have to migrate a JDBC application to JPA. For a
> certain class there are some extra fields in the table that are not in
> the class itself.

How do you know they belong to the class if they are not in the class?
look at the sql, where do these mystery fields come from, are they 
passed in along with the object instance that contains the other fields 
in which case they would need to be contained within some other class if 
it's Java (the horror) are they generated by some stored procedure (the 
horror, the horror) or a trigger (oh the horror).

  (For example creation time, modification time and
> user that created the entity.) Is it possible to keep those fields in
> the table and updated, without putting the values in the class?

Why in [insert deity here]'s name would you want to do that?
Is this some bastard son (of an application) of an unholy alliance 
between a DBA and an OO designer? Why do you want to avoid adding them 
to the class? Is it because, in your Java brain you feel they don't 
'belong' there? If they don't belong in the class then they don't belong 
in the table *unless* they are fields in another class that has some 
sort of containment relationship with your container class? 
(aggregation, composition) in which case they are contained by the 
container class and therefore somehow 'belong' in some 'OO' realty in 
the container.

Trying to map an application to a relational database using a ORM 
framework when some of the fields aren't contained in some way in you 
existential object graph seems a bit like hearding cats ... is it even 
possible, don't know, don't reallyy know JPA but in answer to your othr 
question, as long as you have a driver in your classpath then I can't 
see why you can't use what you want when you want to do what you want.

It all just sounds so ... *nasty*



-- 
Laughing Spam Fritter

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JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-13 20:12 +0200
  Re: JPA and extra fields Eternal Hope <laughingspam99@gmail.com> - 2015-08-13 20:29 +0100
    Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-17 07:40 +0200
  Re: JPA and extra fields Arne Vajhøj <arne@vajhoej.dk> - 2015-08-13 22:30 -0400
    Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-17 08:22 +0200
      Re: JPA and extra fields Martin Gregorie <martin@address-in-sig.invalid> - 2015-08-17 11:40 +0000
        Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-17 14:36 +0200
          Re: JPA and extra fields Martin Gregorie <martin@address-in-sig.invalid> - 2015-08-17 18:08 +0000
            Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-17 21:24 +0200
              Re: JPA and extra fields Martin Gregorie <martin@address-in-sig.invalid> - 2015-08-17 22:47 +0000
                Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-19 11:32 +0200
          Re: JPA and extra fields Arne Vajhøj <arne@vajhoej.dk> - 2015-08-17 19:48 -0400
        Re: JPA and extra fields Eternal Hope <laughingspam99@gmail.com> - 2015-08-18 06:25 +0100
          Re: JPA and extra fields Martin Gregorie <martin@address-in-sig.invalid> - 2015-08-18 10:49 +0000
            Re: JPA and extra fields Eternal Hope <laughingspam99@gmail.com> - 2015-08-19 09:00 +0100
              Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-19 11:36 +0200
                Re: JPA and extra fields Martin Gregorie <martin@address-in-sig.invalid> - 2015-08-19 10:48 +0000
      Re: JPA and extra fields Arne Vajhøj <arne@vajhoej.dk> - 2015-08-17 19:46 -0400
        Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-19 11:28 +0200
    Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-19 11:53 +0200
      Re: JPA and extra fields Martin Gregorie <martin@address-in-sig.invalid> - 2015-08-19 10:51 +0000
        Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-19 13:14 +0200
          Re: JPA and extra fields Cecil Westerhof <Cecil@decebal.nl> - 2015-08-19 14:19 +0200
      Re: JPA and extra fields Arne Vajhøj <arne@vajhoej.dk> - 2015-08-19 19:13 -0400
  Re: JPA and extra fields Silvio <silvio@internet.com> - 2015-08-20 03:49 +0200

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