ServerRuntime cayenneRuntime = new ServerRuntime("cayenne-BlueTwine.xml");
    ObjectContext context = cayenneRuntime.getContext();

    Project project = context.newObject(Project.class); // Add new project to context

    // set some variables on project object

    Div rootDiv = context.newObject(Div.class);

    // set some variables on rootDiv object

    rootDiv.setProject(project);

    context.commitChanges();

    System.out.println(rootDiv.getProject().getId()); // Returns null pointer