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Correct usage of CDO Views [message #1668506]

Thu, 12 March 2015 14:15

Daniel Seybold

Messages: 14
Registered: October 2014

Junior Member

Hi guys,

I'm currently working with a CDO Server and a Client accessing the server.

I'm not sure what is the correct use of the CDO views.

Can it lead to problems if I use the views in this way:

view v = session.openView()
model = resource.getContents().get(0);
v.closeView();
model.doSth();

Thank you in advance for your help!

Cheers,
Daniel

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Re: Correct usage of CDO Views [message #1668515 is a reply to message #1668506]

Thu, 12 March 2015 14:20

Esteban Dugueperoux

Messages: 472
Registered: July 2009

Senior Member

Hi Daniel,

CDOView is usable to a read-only access, if you need read-write access
use a CDOTransaction :

CDOTransaction transaction = session.openTransaction();

Best Regards.

Le 12/03/2015 15:15, Daniel Seybold a écrit :
> Hi guys,
>
> I'm currently working with a CDO Server and a Client accessing the server.
>
> I'm not sure what is the correct use of the CDO views.
>
> Can it lead to problems if I use the views in this way:
>
> view v = session.openView()
> model = resource.getContents().get(0);
> v.closeView();
> model.doSth();
>
> Thank you in advance for your help!
>
> Cheers,
> Daniel

--
Esteban Dugueperoux - Obeo

Need professional services for Sirius?
http://www.obeodesigner.com/sirius

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Re: Correct usage of CDO Views [message #1668532 is a reply to message #1668515]

Thu, 12 March 2015 14:33

Daniel Seybold

Messages: 14
Registered: October 2014

Junior Member

Hi,

thanks for your quick answer.

Now I have a follow up question:

Is the model completely loaded by the

model = resource.getContents().get(0);

command (assuming there is only one root element in this resource) or does the CDO server lazy loading?

Because by

v.closeView();
model.doSth();

I assume the whole model is loaded.

Am I right with this assumption?

Cheers,
Daniel

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Re: Correct usage of CDO Views [message #1669821 is a reply to message #1668532]

Fri, 13 March 2015 01:57

Eike Stepper

Messages: 6483
Registered: July 2009

Senior Member

Am 12.03.2015 um 07:33 schrieb Daniel Seybold:
> Hi,
>
> thanks for your quick answer.
>
> Now I have a follow up question:
>
> Is the model completely loaded by the model = resource.getContents().get(0); command (assuming there is only one root
> element in this resource) or does the CDO server lazy loading?
The latter.

>
> Because by
> v.closeView();
> model.doSth();
You must not close the view until you're done accessing the model that's provided (and managed) by the view/transaction.

>
>
> I assume the whole model is loaded.
No. Unless you've configured prefetching to load it completely.

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper

>
> Am I right with this assumption?
>
> Cheers,
> Daniel

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper

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Re: Correct usage of CDO Views [message #1670926 is a reply to message #1669821]

Fri, 13 March 2015 11:50

Daniel Seybold

Messages: 14
Registered: October 2014

Junior Member

Hi Eike,

thanks a lot. for your answer

This solved all my open issues.

Cheers,
Daniel

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Re: Correct usage of CDO Views [message #1671227 is a reply to message #1670926]

Fri, 13 March 2015 14:15

Alexander Klatt

Messages: 59
Registered: April 2014

Member

Hi,

I have got a related question to the issue about keeping open views/transactions:
is it okay to keep a transaction open for the whole runtime of my application or
should I rather use a view and open the transaction only on demand for a short time?

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Re: Correct usage of CDO Views [message #1671480 is a reply to message #1671227]

Fri, 13 March 2015 16:24

Daniel Seybold

Messages: 14
Registered: October 2014

Junior Member

Hi,

in my understanding of the CDO Server you should use Views if you are just reading the models.

Transactions should be used if you want to write to your models.

E.g. you can open a View (keep the View open), read models and if you want to write just open a Transaction, execute the write actions and commit the Transaction.
If you need to write again later you can open another Transaction.

Cheers,
Daniel

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Re: Correct usage of CDO Views [message #1675856 is a reply to message #1671227]

Sun, 15 March 2015 08:07

Eike Stepper

Messages: 6483
Registered: July 2009

Senior Member

Am 13.03.2015 um 07:15 schrieb Alexander Klatt:
> Hi,
>
> I have got a related question to the issue about keeping open views/transactions: is it okay to keep a transaction
> open for the whole runtime of my application or should I rather use a view and open the transaction only on demand for
> a short time?
Both approaches are possible and common practice.

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper

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