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From JDBC to JPA

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  From JDBC to JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-07-24 17:05 +0200
    Re: From JDBC to JPA Eternal Hope <laughingspam99@gmail.com> - 2015-07-24 17:53 +0100
      Re: From JDBC to JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-07-24 22:03 +0200
        Re: From JDBC to JPA Eternal Hope <laughingspam99@gmail.com> - 2015-07-25 05:23 +0100
          Re: From JDBC to JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-07-25 10:37 +0200
            Re: From JDBC to JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-07-25 23:45 -0400
        Re: From JDBC to JPA Fredrik Jonson <fredrik@jonson.org> - 2015-07-25 08:12 +0000
          Re: From JDBC to JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-07-25 23:49 -0400
        Re: From JDBC to JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-07-25 23:38 -0400
    Re: From JDBC to JPA Joerg Meier <joergmmeier@arcor.de> - 2015-07-24 20:40 +0200
    Re: From JDBC to JPA Jeff Higgins <jeff@invalid.invalid> - 2015-07-24 15:45 -0400
      Re: From JDBC to JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-07-24 22:32 +0200
    Re: From JDBC to JPA Joerg Meier <joergmmeier@arcor.de> - 2015-07-24 22:32 +0200
      Re: From JDBC to JPA Cecil Westerhof <Cecil@decebal.nl> - 2015-07-24 23:18 +0200
    Re: From JDBC to JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-07-25 14:40 -0400
      Re: From JDBC to JPA Arne Vajhøj <arne@vajhoej.dk> - 2015-07-25 23:53 -0400
        Re: From JDBC to JPA Lew <lewbloch@gmail.com> - 2015-08-03 15:43 -0700

#32115 — From JDBC to JPA

I need to change the use of JDBC to JPA in a range of applications. I
am new to JPA. Anyone good tips or links on how to accomplish this?
Until now I did not find anything very useful with Google.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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#32117

On 24/07/2015 16:05, Cecil Westerhof wrote:
> I need to change the use of JDBC to JPA in a range of applications. I
> am new to JPA. Anyone good tips or links on how to accomplish this?
> Until now I did not find anything very useful with Google.

http://openjpa.apache.org/

http://openjpa.apache.org/builds/2.4.0/apache-openjpa/docs/manual.pdf

Is about the best documentation I have found to date.

Rather you than me.

-- 
Laughing Spam Fritter

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#32126

On Friday 24 Jul 2015 18:53 CEST, Eternal Hope wrote:

> On 24/07/2015 16:05, Cecil Westerhof wrote:
>> I need to change the use of JDBC to JPA in a range of applications.
>> I am new to JPA. Anyone good tips or links on how to accomplish
>> this? Until now I did not find anything very useful with Google.
>
> http://openjpa.apache.org/
>
> http://openjpa.apache.org/builds/2.4.0/apache-openjpa/docs/manual.pdf

That the best documentation is for a certain implementation and not
from JPA is a bad omen. :'-(

I need to write clean JPA code, because it should be possible two
switch from Hubernate, to openJPA, to … in a moments notice.


> Is about the best documentation I have found to date.
>
> Rather you than me.

You are confirming my fears. ;-)

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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#32134

On 24/07/2015 21:03, Cecil Westerhof wrote:
> On Friday 24 Jul 2015 18:53 CEST, Eternal Hope wrote:
>
>> On 24/07/2015 16:05, Cecil Westerhof wrote:
>>> I need to change the use of JDBC to JPA in a range of applications.
>>> I am new to JPA. Anyone good tips or links on how to accomplish
>>> this? Until now I did not find anything very useful with Google.
>>
>> http://openjpa.apache.org/
>>
>> http://openjpa.apache.org/builds/2.4.0/apache-openjpa/docs/manual.pdf
>
> That the best documentation is for a certain implementation and not
> from JPA is a bad omen. :'-(

Not sure what you mean by 'from JPA'
JPA is a specification currently 'owned and maintained' by Larry and his 
pals.

Try 
http://www.oracle.com/technetwork/java/javaee/tech/persistence-jsp-140049.html

Although I have to admit that I find the oracle documentation a litte 
dense sometimes.

Check out https://www.jcp.org/en/jsr/detail?id=220 if you want to fry 
your brain


-- 
Laughing Spam Fritter

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#32136

On Saturday 25 Jul 2015 06:23 CEST, Eternal Hope wrote:

> On 24/07/2015 21:03, Cecil Westerhof wrote:
>> On Friday 24 Jul 2015 18:53 CEST, Eternal Hope wrote:
>>
>>> On 24/07/2015 16:05, Cecil Westerhof wrote:
>>>> I need to change the use of JDBC to JPA in a range of
>>>> applications. I am new to JPA. Anyone good tips or links on how
>>>> to accomplish this? Until now I did not find anything very useful
>>>> with Google.
>>>
>>> http://openjpa.apache.org/
>>>
>>> http://openjpa.apache.org/builds/2.4.0/apache-openjpa/docs/manual.pdf
>>
>> That the best documentation is for a certain implementation and not
>> from JPA is a bad omen. :'-(
>
> Not sure what you mean by 'from JPA' JPA is a specification
> currently 'owned and maintained' by Larry and his pals.

I mend that when I am told to read the openJPA documentation instead
of the JPA documentation that I find this not a good sign.


> Try
> http://www.oracle.com/technetwork/java/javaee/tech/persistence-jsp-140049.html
>
> Although I have to admit that I find the oracle documentation a
> litte dense sometimes.
>
> Check out https://www.jcp.org/en/jsr/detail?id=220 if you want to
> fry your brain

I will add your links also.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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#32143

On 7/25/2015 4:37 AM, Cecil Westerhof wrote:
> On Saturday 25 Jul 2015 06:23 CEST, Eternal Hope wrote:
>
>> On 24/07/2015 21:03, Cecil Westerhof wrote:
>>> On Friday 24 Jul 2015 18:53 CEST, Eternal Hope wrote:
>>>
>>>> On 24/07/2015 16:05, Cecil Westerhof wrote:
>>>>> I need to change the use of JDBC to JPA in a range of
>>>>> applications. I am new to JPA. Anyone good tips or links on how
>>>>> to accomplish this? Until now I did not find anything very useful
>>>>> with Google.
>>>>
>>>> http://openjpa.apache.org/
>>>>
>>>> http://openjpa.apache.org/builds/2.4.0/apache-openjpa/docs/manual.pdf
>>>
>>> That the best documentation is for a certain implementation and not
>>> from JPA is a bad omen. :'-(
>>
>> Not sure what you mean by 'from JPA' JPA is a specification
>> currently 'owned and maintained' by Larry and his pals.
>
> I mend that when I am told to read the openJPA documentation instead
> of the JPA documentation that I find this not a good sign.

Don't worry.

It quite common that:
- the official specification of the standard is hard to read
- most people prefer to read:
   - documentation for a specific implementation
   - third party tutorials

My guess is that you did not learn Java from reading the JLS
but instead read either the Java tutorial (from one particular Java
vendor!) or bought a few books.

:-)

If that OpenJPA documentation is good then it will clearly
explain what is standard and maybe provide a few implementation
specific extras.

Arne

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#32135

In <87y4i5mig2.fsf@Equus.decebal.nl> Cecil Westerhof wrote:

>  I need to write clean JPA code, because it should be possible two switch
>  from Hibernate to openJPA in a moments notice.

That is a requirement that is not as easy to fulfill as is appears on first
sight. Especially for someone who does not have experience with JPA already.

I think you'll find that each JPA implementation has its own set of quirks in
performance as well as in configuration. And since you're combining it with a
database, you'll have your database provider's quirks to consider too.

A more reasonable goal is to use only standard JPA annotations for the beans
and most queries, and otherwise aim to limit the provider specific stuff to
parts of the code that you design to be rather easily replaceable when you
decide to try to migrate to another provider. That said, you can get quite far
with plain JPA, at least as long as your database model isn't too complex.

Not to say that JPA is special in this way. Almost every standard that have
multiple implementations also have quirks that are specific to each
implementation. The common case is obviously usually better covered and more
similar between implementations.

On a related theme: Do not be afraid to use native queries when building more
complex queries. There's nothing wrong with JQL, but you do not have the same
control over the details compared to plain SQL.

-- 
Fredrik Jonson

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#32144

On 7/25/2015 4:12 AM, Fredrik Jonson wrote:
> In <87y4i5mig2.fsf@Equus.decebal.nl> Cecil Westerhof wrote:
>
>>   I need to write clean JPA code, because it should be possible two switch
>>   from Hibernate to openJPA in a moments notice.
>
> That is a requirement that is not as easy to fulfill as is appears on first
> sight. Especially for someone who does not have experience with JPA already.
>
> I think you'll find that each JPA implementation has its own set of quirks in
> performance as well as in configuration. And since you're combining it with a
> database, you'll have your database provider's quirks to consider too.
>
> A more reasonable goal is to use only standard JPA annotations for the beans
> and most queries, and otherwise aim to limit the provider specific stuff to
> parts of the code that you design to be rather easily replaceable when you
> decide to try to migrate to another provider. That said, you can get quite far
> with plain JPA, at least as long as your database model isn't too complex.
>
> Not to say that JPA is special in this way. Almost every standard that have
> multiple implementations also have quirks that are specific to each
> implementation. The common case is obviously usually better covered and more
> similar between implementations.
>
> On a related theme: Do not be afraid to use native queries when building more
> complex queries. There's nothing wrong with JQL, but you do not have the same
> control over the details compared to plain SQL.

It is my impression that a lot of people (maybe the large majority of
people) are able to do with only standard JPA code - maybe with a small
dose of standard SQL where necessary.

Arne

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#32142

On 7/24/2015 4:03 PM, Cecil Westerhof wrote:
> On Friday 24 Jul 2015 18:53 CEST, Eternal Hope wrote:
>> On 24/07/2015 16:05, Cecil Westerhof wrote:
>>> I need to change the use of JDBC to JPA in a range of applications.
>>> I am new to JPA. Anyone good tips or links on how to accomplish
>>> this? Until now I did not find anything very useful with Google.
>>
>> http://openjpa.apache.org/
>>
>> http://openjpa.apache.org/builds/2.4.0/apache-openjpa/docs/manual.pdf
>
> That the best documentation is for a certain implementation and not
> from JPA is a bad omen. :'-(
>
> I need to write clean JPA code, because it should be possible two
> switch from Hubernate, to openJPA, to … in a moments notice.

Just use the JPA API and not anything from implementation API
and you should be on the right track.

Arne

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#32122

On Fri, 24 Jul 2015 17:05:15 +0200, Cecil Westerhof wrote:

> I need to change the use of JDBC to JPA in a range of applications. I
> am new to JPA. Anyone good tips or links on how to accomplish this?
> Until now I did not find anything very useful with Google.

One tip: there are multiple (I think Eclipselink, Hibernate, some 3rd
party) tools to generate JPA-Annotated .java files from your database
schema. That alone tends to end up a huge time saver.

Liebe Gruesse,
		Joerg

-- 
Ich lese meine Emails nicht, replies to Email bleiben also leider
ungelesen.

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#32125

On 07/24/2015 11:05 AM, Cecil Westerhof wrote:
> I need to change the use of JDBC to JPA in a range of applications. I
> am new to JPA. Anyone good tips or links on how to accomplish this?
> Until now I did not find anything very useful with Google.
>
Maybe this is not one of the not very useful articles you've found.
Migrating JDBC Data Access Objects to use EJB3
<http://www.theserverside.com/news/1364373/Migrating-JDBC-Data-Access-Objects-to-use-EJB3>

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#32128

On Friday 24 Jul 2015 21:45 CEST, Jeff Higgins wrote:

> On 07/24/2015 11:05 AM, Cecil Westerhof wrote:
>> I need to change the use of JDBC to JPA in a range of applications.
>> I am new to JPA. Anyone good tips or links on how to accomplish
>> this? Until now I did not find anything very useful with Google.
>>
> Maybe this is not one of the not very useful articles you've found.
> Migrating JDBC Data Access Objects to use EJB3
> <http://www.theserverside.com/news/1364373/Migrating-JDBC-Data-Access-Objects-to-use-EJB3>

No, it was not. I put it on my list.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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#32127

On Fri, 24 Jul 2015 17:05:15 +0200, Cecil Westerhof wrote:

> I need to change the use of JDBC to JPA in a range of applications. I
> am new to JPA. Anyone good tips or links on how to accomplish this?
> Until now I did not find anything very useful with Google.

<http://stackoverflow.com/questions/6033905/create-the-perfect-jpa-entity>

May also be a good read for you.

Liebe Gruesse,
		Joerg

-- 
Ich lese meine Emails nicht, replies to Email bleiben also leider
ungelesen.

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#32130

On Friday 24 Jul 2015 22:32 CEST, Joerg Meier wrote:

> On Fri, 24 Jul 2015 17:05:15 +0200, Cecil Westerhof wrote:
>
>> I need to change the use of JDBC to JPA in a range of applications.
>> I am new to JPA. Anyone good tips or links on how to accomplish
>> this? Until now I did not find anything very useful with Google.
>
> <http://stackoverflow.com/questions/6033905/create-the-perfect-jpa-entity>
>
> May also be a good read for you.

I have something to do this weekend. ;-)

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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#32140

On 7/24/2015 11:05 AM, Cecil Westerhof wrote:
> I need to change the use of JDBC to JPA in a range of applications. I
> am new to JPA. Anyone good tips or links on how to accomplish this?
> Until now I did not find anything very useful with Google.

Google of JPA tutorial did not provide anything useful?

There are a lot of tutorials out there.

Arne

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#32145

On 7/25/2015 2:40 PM, Arne Vajhøj wrote:
> On 7/24/2015 11:05 AM, Cecil Westerhof wrote:
>> I need to change the use of JDBC to JPA in a range of applications. I
>> am new to JPA. Anyone good tips or links on how to accomplish this?
>> Until now I did not find anything very useful with Google.
>
> Google of JPA tutorial did not provide anything useful?
>
> There are a lot of tutorials out there.

A few random:

https://docs.oracle.com/javaee/7/tutorial/partpersist.htm

http://www.tutorialspoint.com/jpa/index.htm

http://www.vogella.com/tutorials/JavaPersistenceAPI/article.html

http://www.javaworld.com/article/2077817/java-se/understanding-jpa-part-1-the-object-oriented-paradigm-of-data-persistence.html

Arne

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#32255

Cecil Westerhof wrote:
> >> I need to change the use of JDBC to JPA in a range of applications. I
> >> am new to JPA. Anyone good tips or links on how to accomplish this?
> >> Until now I did not find anything very useful with Google.

JPA is not a replacement for JDBC generally.

You use JDBC when you think of a persistent store as a set of data tables.

You use JPA when you think of persistent objects.

The ontologies differ.

JDBC you don't have 'EntityManager', you have transactions, you have artificial ID fields declared as "INTEGER", you have rows and columns.

JPA you have objects in a managed state, that own relationships to other object types. (Not relations!) You don't want or use a DAO approach. You shouldn't ever link objects via an ID field, or even expose it in the model.

Good luck. To the degree that you use JPA fro a data mindset instead of an object one, you will be screwed.

-- 
Lew

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