hibernate-devel

[Hibernate] Lazy Collections

[Jonas V. P. <jvp...@ti...>]

The implementation of the write() method in cirrus.hibernate.collections.=
PersistentCollection
states:

	protected final void write() {
		initialize(true);
		if ( session!=3Dnull && session.isOpen() ) session.dirty(this);
	}

This means the session needs to be open.
Also, the Docs mentions that lazy collections need to have an open sessio=
n.
Could we safely modify the code to reopen the session when needed?
	protected final void write() {
		initialize(true);
		if ( session !=3D null ) {
                    if ( session.isOpen() ) {
                        session.dirty(this);
                    } else {
                        // Re-open session
                        session.reopen(); // ommitted try-catch
                        session.dirty(this);
                    }
                }
	}


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******
Hou uw internetverbruik beter onder controle ... surf met Tiscali Complet=
e
... http://tiscali.complete.be

RE: [Hibernate] Lazy Collections

[Aapo L. <aap...@pr...>]

> The implementation of the write() method in
> cirrus.hibernate.collections.PersistentCollection
> states:
> 
> This means the session needs to be open.
> Also, the Docs mentions that lazy collections
> need to have an open session.

Gavin:

I have also other problems with lazy collections. I get WARNings about
Unclosed Sessions (finalize method in SessionImpl). I use Maverick Web
MVC Framework and it has discard() method in one interface that you can
implement. I have put my Session closing code in it, but it doesn't
help. It continues to leave sessions open. I have tried almost
everything, but I cannot get rid of those Unclosed Sessions. Only
solution I have found is closing session before going to a view
rendering phase, and that means that lazy initialization is not an
option anymore.

Also I see that Hibernate uses a lot of finally {} blocks to do some
cleaning. If I understand correctly, at least what I have read from some
of IBM's whitepapers, they don't recommend you to use finally {} to do a
cleaning (mainly they don't recommend to put connection closing code in
it) as it cannot be determined when that block gets called. I migth be
wrong, but I can get the article if you like (?).

Any ideas? Do you want the example code that leaves connections some
times open (ie. under load)?

For resin users:

You should enable...

<ignore-client-disconnect>true</ignore-client-disconnect>

... if you don't, you are going to get potential problems. i.e. resin
starts executing the code, but meanwhile client disconnects and resin
recognices that and then immediately stops code execution (you can
demonstrate this by yourself by using e.g. Internet Explorer and then
hit a page and push F5 key down for about 15 seconds). What this means
in practice is that if you close connections after serving client, then
that code never gets executed -> you are going to run out of db
connections that you have in some pool (i.e. jndi). I think that this
settings should be put in some FAQ.

Kind Regards
Aapo Laakkonen

Re: [Hibernate] Lazy Collections

[Brad C. <bra...@wo...>]

> I have also other problems with lazy collections. I get WARNings about
> Unclosed Sessions (finalize method in SessionImpl). I use Maverick Web
> MVC Framework and it has discard() method in one interface that you can
> implement. I have put my Session closing code in it, but it doesn't
> help. It continues to leave sessions open. I have tried almost
> everything, but I cannot get rid of those Unclosed Sessions. Only
> solution I have found is closing session before going to a view
> rendering phase, and that means that lazy initialization is not an
> option anymore.

on the project i am currently working on we use a servlet filter to open a
connection in a try block and stick the close connection in a finally block.
we r not having any probs with lazy initialisation or unclosed sessions.
however, we r also not using the absolute latest version of hibernate.

> Also I see that Hibernate uses a lot of finally {} blocks to do some
> cleaning. If I understand correctly, at least what I have read from some
> of IBM's whitepapers, they don't recommend you to use finally {} to do a
> cleaning (mainly they don't recommend to put connection closing code in
> it) as it cannot be determined when that block gets called. I migth be

u definitely don't want to rely on finally blocks to clean up connections,
sockets, etc. when it can/should be done some other way.  however, aren't
they the last line of defence when u r relying on someone else to clean up
after themselves?   for example, only the developer of the client app knows
when they r finished with a session and therefore when to close it.

regards
brad

Re: [Hibernate] Lazy Collections

[Max R. A. <ma...@eo...>]

No! If an session has been closed forcefully or by other means, hibernate
internals should not reopen the session - at least not per default! If the
session has been closed there is a reason for it - one might be to ensure
that the ui-layer does not accidently fetches data by "dotting" around in
the object graph.

If you want the session to be (re)opend - why don't you just keep the
session open ?

/max

----- Original Message -----
From: "Jonas Van Poucke" <jvp...@ti...>
To: "Hibernate Developers" <hib...@li...>
Sent: Tuesday, December 03, 2002 9:20 AM
Subject: [Hibernate] Lazy Collections


The implementation of the write() method in
cirrus.hibernate.collections.PersistentCollection
states:

protected final void write() {
initialize(true);
if ( session!=null && session.isOpen() ) session.dirty(this);
}

This means the session needs to be open.
Also, the Docs mentions that lazy collections need to have an open session.
Could we safely modify the code to reopen the session when needed?
protected final void write() {
initialize(true);
if ( session != null ) {
                    if ( session.isOpen() ) {
                        session.dirty(this);
                    } else {
                        // Re-open session
                        session.reopen(); // ommitted try-catch
                        session.dirty(this);
                    }
                }
}


****************************************************************************
***
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... http://tiscali.complete.be





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