In 4.2.8.Final the the class MapKeyHelpers.MapKeySource has the Method "getPathIdentifier()" overridden which retrieves the PathIdentifier from the class-local-object "mapJoin". In version 4.3.1.Final that Version is missing.

@Override
public String getPathIdentifier() {
	return mapJoin.getPathIdentifier();
}

In the 4.2-Branch that method was introduced with commit "https://github.com/hibernate/hibernate-orm/commit/c421d7014b0a8b1270c34da01574837e9c4dbc36" on August 2012 with comment to