Xtext:如何实现IQualifiedNameProvider来返回文件名

import org.eclipse.xtext.naming.DefaultDeclarativeQualifiedNameProvider;
import org.eclipse.xtext.naming.QualifiedName;

public class MyQualifiedNameProvider extends DefaultDeclarativeQualifiedNameProvider {

    @Override
    public QualifiedName getFullyQualifiedName(EObject obj) {
        if (obj instanceof MyElement) {
            MyElement element = (MyElement) obj;
            String fileName = element.eResource().getURI().lastSegment();
            return QualifiedName.create(fileName);
        }
        return null;
    }
}

<extension point="org.eclipse.xtext.resource.IResourceServiceProvider">
    <resourceServiceProvider
        uriExtension="mydsl"
        class="com.example.MyDslResourceServiceProvider">
        <fileExtensions
            contentTypeIdentifier="org.eclipse.xtext.resource.genericdsl.GenericDsl"
            fileExtension="mydsl"/>
    </resourceServiceProvider>
</extension>