JAVAFX Concurency with querying the DB

Question

I'm building an application using JAVAFX over JAVA8. In my app i have a data grid that should populate with result set from the DB. However, the query may take a while and I don't want the GUI to be idle until that.

What is the best Thread architecture for that kind of issue?

I thought about using a Task for the query itself and than put the outcome it in the data grid. However, The main UI Thread doesn't allows other thread to touch the objects. And if I just wait for the thread to end, it becomes a sync process (which i want to avoid of)

Any Ideas?

score 0 · Accepted Answer · answered May 13 '14 at 19:27

I would go for that task. It is always a good idea to have long running operations on the background so the UI doesn't freeze up. Furthermore, you can think about paging (by scrolling down in a table for example, or prev and next buttons)

Here is how I would do it using a Task

    final Task<List<User>> searchUserTask = new Task<List<User>>() {
        @Override
        protected List<User> call() throws Exception {
              //search logic, for example call to DB
              return //list of users
        }

    };

    //Here we add a listener to the state, so that we can know when the operation finishes, and decide what to do after
    searchUserTask.stateProperty().addListener((ObservableValue<? extends Worker.State> source, Worker.State oldState, Worker.State newState) -> {

        if (newState.equals(Worker.State.SUCCEEDED)) { //the operation finished successfully
            List<User> result = searchTask.getValue();
            //set value to a UI component (this method runs on the UI thread)
            //usersTable.getItems().setAll(matches);
        } else if (newState.equals(Worker.State.FAILED)) {
            Throwable exception = searchTask.getException();
            log.error("Contact search failed", exception);
        }
    });

    new Thread(searchUserTask).start();

So here you have a way that somewhat simulates a callback mechanism. You add a listener to the state, when it changes, the event will automatically fire, and its upto you to properly catch it, and than handle the success state etc.

JAVAFX Concurency with querying the DB

1 Answers1