//Init a project and a workspace
ProjectController pc = Lookup.getDefault().lookup(ProjectController.class);
pc.newProject();
Project project = pc.getCurrentProject();
Workspace workspace = project.getLookup().lookup(WorkspaceProvider.class).getCurrentWorkspace();

//Import file
ImportController importController = Lookup.getDefault().lookup(ImportController.class);
FileImporter fileimp = importController.getFileImporter("graphml");
Container container = importController.importFile(new File("data/examplefile.graphml"));
importController.process(container, new DefaultProcessor(), workspace);

//Print the column values
GraphModel model = Lookup.getDefault().lookup(GraphController.class).getGraphModel(workspace);

System.out.println("----------------\nColumns for node:\n----------------");

for(Node n : model.getGraph().getNodes())
{
    System.out.println("label:" + n.getAttribute("label"));
    System.out.println("someidfornode:" + n.getAttribute("someidfornode"));

    //Throws an error
    try
    {
        System.out.println("d3:" + n.getAttribute("d3"));
    }
    catch(Exception ex)
    {
        ex.printStackTrace();
    }
}

System.out.println("----------------\nColumns for edge:\n----------------");

for(Edge e : model.getGraph().getEdges())
{
    System.out.println("label:" + e.getAttribute("label"));
    System.out.println("someidforedge:" + e.getAttribute("someidforedge"));

    //Throws an error
    try
    {
        System.out.println("d7:" + e.getAttribute("d7"));
    }
    catch(Exception ex)
    {
        ex.printStackTrace();
    }
}