Description Christopher Gerking 2022-01-18 14:42:29 EST

If a transformation includes workspace blackboxes, serializing and reloading that transformation to/from *.qvtox fails with an IllegalArgumentException "imported module must be in a resource". The failure is due to a bad choice of the artificial URIs used by QVTo to reference blackbox units. These blackbox URIs have the following form:

qvto://blackbox/org.eclipse.m2m.qvt.oml.MyBlackboxUnit?jdt#MyJavaProject

What are they used for? To indicate that BlackboxResourceFactory must be used when resolving a blackbox unit referenced by a *.qvtox file. BlackboxResourceFactory registers a parser for the qvto:// protocol, which then delegates the creation and loading of units to the blackbox mechanism.

The problem is the use of the fragment to encode the Java project in which a blackbox unit resides. A fragment usually represents a specific model element inside a unit, not the unit itself. Thus fragments are trimmed during EMF's default XMI serialization, so that URIs are serialized incompletely in the following form:

qvto://blackbox/org.eclipse.m2m.qvt.oml.MyBlackboxUnit?jdt

Obviously the above URI lacks an indication of the project and thus can't be resolved to a blackbox unit. Adjusting the *.qvtox serialization to our needs is possible but relatively cumbersome. Instead, the form of the URIs should be changed so that the Java project is encoded by the query:

qvto://blackbox/org.eclipse.m2m.qvt.oml.MyBlackboxUnit?jdt=MyJavaProject

This way, the fragment no longer encodes the project, so the URIs are intact using the default XMI serialization.