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Saving/Loading to/from BinaryResourceImpl [message #1383901]

Tue, 27 May 2014 06:10

Markus Duft

Messages: 148
Registered: February 2013

Senior Member

Hey

I have some code to persist a linked/merged/patched/whatever xtext dsl based EMF model to a BinaryResourceImpl, and re-read it from such. This seems to work rather well, however, when re-reading the model from the resource, it seems to disappear suddenly. I have this method:

        def load(InputStream binary) {
		try {
			val bin = resourceSet.createResource(URI.createURI("http://www.wamas.com/dummy.wdlbin"));
			
			bin.load(binary, binaryResourceOptions);
			
			contents = bin.allContents.toIterable.filter(TopLevelElement)
			packages = bin.allContents.toIterable.filter(Package)
		} finally {
			binary.close
		}
	}

when i set a breakpoint at the end of the method, the contents looks ok. All elements that i'd expect are there. When i step out of this method, contents disappears (is an empty collection then).

What the heck is going on here? what am i missing? any ideas? Thanks!

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Re: Saving/Loading to/from BinaryResourceImpl [message #1383903 is a reply to message #1383901]

Tue, 27 May 2014 06:25

Markus Duft

Messages: 148
Registered: February 2013

Senior Member

i debugged a little in the generated code and recorded a screencast of how the collection magically empties...: http://dev.gentoo.org/~mduft/screencast_xtend.webm

there are a few strange things i can see here:

1) the _allContents collection is shown as empty, however the _filter is initially NOT empty.
2) when hovering over _filter right after the line is executed, it is non-empty.
3) when hovering over _filter a second time it is suddenly empty.

WTF is going on here?

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Re: Saving/Loading to/from BinaryResourceImpl [message #1383904 is a reply to message #1383903]

Tue, 27 May 2014 06:29

Markus Duft

Messages: 148
Registered: February 2013

Senior Member

if i change the contents and package assignment to this it works:

contents = resourceSet.resources.map(r|r.allContents.toIterable).flatten.filter(TopLevelElement)
packages = resourceSet.resources.map(r|r.allContents.toIterable).flatten.filter(Package)

still: some ideas?

[Updated on: Tue, 27 May 2014 06:29]

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Re: Saving/Loading to/from BinaryResourceImpl [message #1383907 is a reply to message #1383903]

Tue, 27 May 2014 06:52

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

It may be caused by guava expressions being lazy. Some assignments
may force an actual execution

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Saving/Loading to/from BinaryResourceImpl [message #1383942 is a reply to message #1383901]

Tue, 27 May 2014 10:27

Ed Willink

Messages: 7655
Registered: July 2009

Senior Member

Hi

A common problem with persistence is accidentally neglecting to define
the reference as containment, or defining it as transient/volatile.

A common problem while running is child-stealing, adding an object as a
child of a new container removes it from an old container.

For non-trivial models child-stealing can cause such obscure problems
that I add

@Override
protected void eBasicSetContainer(InternalEObject newContainer, int
newContainerFeatureID) {
if (newContainer != null) {
EObject oldContainer = eContainer();
assert ((oldContainer == null) || (newContainer ==
oldContainer) || (oldContainer.eResource() == null));
}
super.eBasicSetContainer(newContainer, newContainerFeatureID);
}

@Override
public NotificationChain eBasicSetContainer(InternalEObject
newContainer, int newContainerFeatureID, NotificationChain msgs) {
if (newContainer != null) {
EObject oldContainer = eContainer();
assert ((oldContainer == null) || (newContainer ==
oldContainer) || (oldContainer.eResource() == null));
}
return super.eBasicSetContainer(newContainer,
newContainerFeatureID, msgs);
}

to my root XXXEObjectImpl.

Minor downside; if you really want to reparent an EObject you must
explicitly set its parent to null in the interim.

Regards

Ed Willink

On 27/05/2014 07:10, Markus Duft wrote:
> Hey
>
> I have some code to persist a linked/merged/patched/whatever xtext dsl
> based EMF model to a BinaryResourceImpl, and re-read it from such.
> This seems to work rather well, however, when re-reading the model
> from the resource, it seems to disappear suddenly. I have this method:
>
>
> def load(InputStream binary) {
> try {
> val bin =
> resourceSet.createResource(URI.createURI("http://www.wamas.com/dummy.wdlbin"));
>
> bin.load(binary, binaryResourceOptions);
>
> contents = bin.allContents.toIterable.filter(TopLevelElement)
> packages = bin.allContents.toIterable.filter(Package)
> } finally {
> binary.close
> }
> }
>
>
> when i set a breakpoint at the end of the method, the contents looks
> ok. All elements that i'd expect are there. When i step out of this
> method, contents disappears (is an empty collection then).
>
> What the heck is going on here? what am i missing? any ideas? Thanks!

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Re: Saving/Loading to/from BinaryResourceImpl [message #1383943 is a reply to message #1383942]

Tue, 27 May 2014 10:38

Markus Duft

Messages: 148
Registered: February 2013

Senior Member

thanks for the hints.

@Ed: thanks for the insight, very good to keep that in mind Smile

In this case i don't think that i have this kind of problem. I verified that the model is persisted correctly (all elements are in the file), and that it is read correctly (model.contents contains all root elements, and in the debugger i can have a look at them). Just right after "bin.allContents.toIterable.filter(TopLevelElement)" the returned collection is filled, and half a second later it's empty, without any (obvious, in the current thread) code running...

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