Get EPackage of .ecore file

[glsp-bot]

In order to generate a genmodel for code generation for an .ecore file I need to get get the EPackage for the file. I have tried some things but I'm not able to archive this.

As a reference I use this answer for the creation of the genmodel.
https://www.eclipse.org/forums/index.php?t=msg&th=513278&goto=1096737&#msg_1096737

He noted the following:
Please note that this generates a gen model file based on an existing ecore model which has already been imported into an EPackage by reading it using a Resource. Also, not shown here, the resource associated to the EPackage needs to have its URI set to the correct ecore file.

Basically I'm not able to produce the correct EPackage rootPackage which is needed in the code of the link.

original thread by Leo Knoll

[CamilleLetavernier]

In EMF, Resources are used to represent/load (and save) the contents of a File (In this case, load the EPackage from the *.ecore file)
Since resources often have dependencies, they are regrouped in a ResourceSet.
So, to load the EPackage from an existing *.ecore file, you need:

• A ResourceSet (new ResourceSetImpl())

• A URI to your *.ecore file (In an eclipse workspace: URI.createPlatformResourceURI('//<myFile.ecore>', or with absolute paths: URI.createFileURI('absolutePath')

• Then you can load the Resource corresponding to this URI from the Resource Set:

```Resource ecorePackageResource = resourceSet.getResource(uri, true); // Only use loadOnDemand=true if you know that the file already exists```

And then you can explore the contents of this resource to find the loaded EPackage (Usually, it's the first root element). An optimistic/simplified version:

```EPackage ecorePackage = (EPackage)resource.getContents().get(0);```

[glsp-bot]

[Leo Knoll]

Thanks a lot, I was already on the right track but did not understand the Resource system...
Only thing missing was to register the ResourceFactory
resourceSet.getResourceFactoryRegistry().getExtensionToFactoryMap().put('ecore', new XMIResourceFactoryImpl());

[CamilleLetavernier]

Ah, yes; in an Eclipse Application this is done automatically; but in a plain Java application you indeed need to register a few things manually

[glsp-bot]

[Jonas Ebel]

Hey I have a follow up issue on this question: When I run the genmodel generation in a docker container I get the exception:

```root ERROR Ecore Gen: Exception in thread 'main' 
root ERROR Ecore Gen: java.lang.RuntimeException: Cannot create a resource for 'file:/usr/src/client/workspace'; a registered resource factory is needed
    at org.eclipse.emf.ecore.resource.impl.ResourceSetImpl.getResource(ResourceSetImpl.java:394)
    at com.codegen.GenmodelGenerator.createGenModel(GenmodelGenerator.java:82)
    at com.codegen.GenmodelGenerator.main(GenmodelGenerator.java:57)```

I have a node-alpine running with openjdk-11 on the path. When I execute this command in my linux machine, I do not get this exception.
Do you have an idea, what this might be causing the exception?

[glsp-bot]

[Leo Knoll]

It was because of the registering, this one fixes it instead of the previous way it was registered:
resourceSet.getResourceFactoryRegistry().getExtensionToFactoryMap().put('ecore', new EcoreResourceFactoryImpl()); resourceSet.getResourceFactoryRegistry().getExtensionToFactoryMap().put('*', new XMIResourceFactoryImpl());