How to ensure load from db when rendering ?

Vaadin 6 / 7 / 8
1

Hi
I am new to Vaadin for 2 days. I am blocked by a simple question : How to ensure load from db when rendering ?
In my UI class , I create a HorizontalSplitPanel . When user clicks the left tree , right panel renders correspondent view.
The problem is , the right panel caches the data loaded from DB. It cannot reflects the latest state in DB.

The right panel contains two component . countLabel , and mTable .
countLabel shows how many users in DB . and mTable loads/displays them.

@SpringComponent
public class UsersView extends VerticalLayout {

  @Inject
  private UserDao userDao;

  @PostConstruct
  void init() {
    Label countLabel = new Label(new AbstractProperty<String>() {
      @Override
      public String getValue() {
        return String.valueOf(userDao.count());
      }

      @Override
      public void setValue(String newValue) throws ReadOnlyException {

      }

      @Override
      public Class<? extends String> getType() {
        return String.class;
      }
    });

    addComponent(countLabel);

    final int pageSize = 10;
    MTable<User> mTable = new MTable<>(User.class,
      i -> {
        return userDao.list(1, pageSize);
      },
      () -> (int) userDao.count() ,  pageSize
     )
      .withProperties("id", "name")
      ;
    mTable.refreshRows();
    mTable.setSizeFull();
    addComponent(mTable);
  }
}

I want Vaadin to display correct countLabel (user count) and userList (mTable) upon each rendering.
But it seems only countLabel works correctly (But I feel it is tedious , anyway to improve/shorten it ?) .

The mTable is cached forever.

If the user navigates to other component and back (by clicking the left tree node) , if DB state changes (user added or removed) , countLabel shows correctly , but mTable doesn’t reflect the true state.

Even the user refresh the browser , the mTable still displays stale data.

How to fix such issue ?

(The UsersView is injected to my UI class )

Environment :
spring-boot 1.3.3
vaadin-spring-boot-starter : 1.0.0
viritin : 1.47

2

I solve the problem by introducing another customized interface : Reloadable

public interface Reloadable { void reload(); } And my views implement this interface :

@SpringComponent
public class TeachersView extends VerticalLayout implements Reloadable {

  @Inject
  private TeacherDao teacherDao;

  private final static int PAGESIZE = 10;

  private MTable<Teacher> mTable = new MTable<>(Teacher.class);

  @PostConstruct
  public void init() {
    mTable.setSizeFull();
    // other mTable settings ...

    reload();
    addComponent(mTable);
  }

  @Override
  public void reload() {
    mTable.setBeans(new SortableLazyList<>(
      sortablePagingProvider ,
      () -> (int) teacherDao.count() ,
      PAGESIZE
    ));
  }

  private SortableLazyList.SortablePagingProvider<Teacher> sortablePagingProvider =
    (firstRow, asc, sortProperty) -> {
      logger.info("teacherDao.findAll ...");
      return teacherDao.findAll(
        new PageRequest(
          firstRow / PAGESIZE, PAGESIZE,
          asc ? Sort.Direction.ASC : Sort.Direction.DESC,
          sortProperty == null ? "id" : sortProperty
        )
      ).getContent();
    };
}

And in the UI class :

@SpringUI(path = "/ui")
@Theme("valo")
public class VaadinUI extends UI {

  @Inject
  private TeachersView teachersView;

  // other injected views skipped

  @Override
  protected void init(VaadinRequest vaadinRequest) {
    
    Panel panel = new Panel("Admin Panel");

    HorizontalSplitPanel splitPanel = new HorizontalSplitPanel();
    splitPanel.setSplitPosition(15, Unit.PERCENTAGE);
    panel.setContent(splitPanel);

    Tree tree = new Tree("Menu");
    splitPanel.setFirstComponent(tree);

    Label home = new Label("Home");

    Map<String, Component> map = new HashMap<>();
    map.put("Teachers", teachersView);
    // other views

    map.forEach((k, v) -> tree.addItem(k));

    tree.addItemClickListener(event -> {
      Component view = map.get(event.getItemId());
      if (view instanceof Reloadable) {
        Reloadable reloadable = (Reloadable) view;
        reloadable.reload();
      }
      splitPanel.setSecondComponent(view);
    });

    splitPanel.setSecondComponent(home);

    setContent(panel);
  } // init()

}

It works !
But I don’t know if it the proper or
standard
 way achieving this ?
Is it the
vaadin
 way ? Or anything built-in I can follow ? Thanks.