Load EMF model instance from XMI file

The reason was, I did not generate the model codes. Because of that, 'List' package could not be found. I did add it to my packageRegistry and that's all.

        ResourceSet resourceSet = new ResourceSetImpl();

        // register UML
        Map packageRegistry = resourceSet.getPackageRegistry();
        packageRegistry.put(list.ListPackage.eNS_URI, list.ListPackage.eINSTANCE);

        // Register XML resource as UMLResource.Factory.Instance
        Map extensionFactoryMap = Resource.Factory.Registry.INSTANCE.getExtensionToFactoryMap();
        extensionFactoryMap.put("xmi", new XMIResourceFactoryImpl());

        Resource resource = (Resource) resourceSet.createResource(uri);


        // try to load the file into resource
        resource.load(null);