ExercService Version for JavaFX

Question

I made a Java utility that does a search inside XML inside the x number of fancy zip files (twx).

This was originally a command line utility and did not perform threading.

When I moved it to use JavaFX, I ran into problems with freezing, and then translated all the searches into the task object that needs to be fixed.

I needed a way to track progress, so I implemented the Progress and ProgressBar property for tracking.

This worked fine, but since I'm already multi-threaded, why not create a thread for each Zip search. Unfortunately, this did not work.

To track, I create an array of tasks, and then the main task that processes them. I use progress and general properties that handle all updates.

Here is the code

public class TextSearch { final private SimpleDoubleProperty progress = new SimpleDoubleProperty(); final private SimpleDoubleProperty total = new SimpleDoubleProperty(); /** * * Kicks off a search. Creates a Task/Thread for each twx search. * @return A task object that maintains all of the twx searches. * * @throws ZipException If the zip file is unreadable. * @throws IOException If the file is unreadable. * @throws JDOMException If the xml in the files are unreadable. * @throws InvalidTWXFile If the twx is corrupt. */ public Task<?> executeSearch() throws ZipException, IOException, JDOMException, InvalidTWXFile { //Loop through all registered twx files. Iterator<TWExport> rit = registered.iterator(); Integer t = 0; //Create a task for each search final ArrayList<Task<?>> tasks = new ArrayList<Task<?>>(); while(rit.hasNext()) { final TWExport twx = rit.next(); //Only run search if user selects to search it. if(twx.getSearchEnabled()) { Task<Void> task = new Task<Void>() { @Override public Void call() { informUser("Searching " + twx); SearchResults proj = new SearchResults(twx); searchResult.add(proj); searchTwx(proj,twx); twx.setResultCount(proj.getTotalCount()); informUser("Finished Searching " + twx); try { Thread.sleep(1000); } catch (InterruptedException e) { if (isCancelled()) { updateMessage("Cancelled"); } } return null; } }; tasks.add(task); t += twx.getObjects().size(); } else { informUser("Skipping " + twx); } } total.setValue(t); //Create the main thread that will hold all individual searches. Task<Void> main = new Task<Void>() { @Override protected Void call() throws Exception { startTime = new Date(); Iterator<Task<?>> it = tasks.iterator(); while(it.hasNext()) { Thread t = new Thread(it.next()); t.start(); } //Sometimes I get a hung thread in this loop while(!progress.getValue().equals(total.getValue())) { updateProgress(progress.getValue(), total.getValue()); Thread.sleep(5000); } setEndTime(new Date()); return null; } }; new Thread(main).start(); return main; } /** * Search through a twx file and add results to the project search results * @param proj The parent SearchResults * @param twx The TWExport to search */ private void searchTwx(SearchResults proj, TWExport twx) { Iterator<TWObject> it = twx.getObjects().iterator(); //Iterate through the files and get the result while(it.hasNext()) { TWObject object = it.next(); progress.setValue(progress.getValue() + 1); if(searchArtifacts.matcher(object.getName()).find()) { SearchResults result = object.searchContents(searchStr); if(result != null) { proj.add(result); } } } } 

Using the main thread seems very awkward, and sometimes it freezes in this loop when searching for 10 + zip files at a time.

Is there a better way to do this with an unknown amount of tasks? Is there something like a JavaFX ExecutorService where I can add a bunch of tasks, let it go and control progressProperty?

Answer 1

There is no need for a specific JavaFX executor service: regular java.util.concurrent.ExecutorService works just fine, since Task is a subclass of FutureTask .

Once you have a list of tasks, you can calculate the overall progress as a function of the progress of each of them. For example, it may just be the sum of the progress of all, divided by the number of tasks. If each task has a different number of items to process, you can do something more complex.

Here's a simple SSCCE:

 import java.util.ArrayList; import java.util.List; import java.util.Random; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.stream.Collectors; import javafx.application.Application; import javafx.beans.binding.DoubleBinding; import javafx.beans.property.DoubleProperty; import javafx.beans.property.IntegerProperty; import javafx.beans.property.SimpleDoubleProperty; import javafx.beans.property.SimpleIntegerProperty; import javafx.concurrent.Task; import javafx.concurrent.Worker; import javafx.geometry.Insets; import javafx.geometry.Pos; import javafx.scene.Scene; import javafx.scene.control.Button; import javafx.scene.control.Label; import javafx.scene.control.ProgressBar; import javafx.scene.control.TextArea; import javafx.scene.layout.BorderPane; import javafx.scene.layout.Priority; import javafx.scene.layout.VBox; import javafx.stage.Stage; public class MultipleTaskTest extends Application { private final ExecutorService exec = Executors.newFixedThreadPool(5, r -> { Thread t = new Thread(r); t.setDaemon(true); return t ; }); private final Random rng = new Random(); @Override public void start(Stage primaryStage) { Label pendingTasksLabel = new Label(); Button button = new Button("Launch tasks"); TextArea log = new TextArea(); DoubleProperty progress = new SimpleDoubleProperty(1); ProgressBar progressBar = new ProgressBar(); progressBar.progressProperty().bind(progress); IntegerProperty pendingTasks = new SimpleIntegerProperty(0); pendingTasksLabel.textProperty().bind(pendingTasks.asString("Pending Tasks: %d")); button.disableProperty().bind(pendingTasks.greaterThan(0)); button.setOnAction(e -> { int numTasks = rng.nextInt(5) + 4 ; List<Task<Void>> tasks = new ArrayList<>(); for (int i = 0; i < numTasks; i++) { tasks.add(createRandomTask()); } // rebind progress: progress.unbind(); progress.bind( new DoubleBinding() { { for (Task<Void> task : tasks) { bind(task.progressProperty()); } } @Override public double computeValue() { return tasks.stream().collect(Collectors.summingDouble( task -> Math.max(task.getProgress(), 0) )) / numTasks; } }); log.appendText("Submitting "+numTasks+" tasks\n"); pendingTasks.set(numTasks); // log state of each task: tasks.forEach(task -> task.stateProperty().addListener((obs, oldState, newState) -> { log.appendText("\tTask "+newState+"\n"); // update pendingTasks if task moves out of running state: if (oldState == Worker.State.RUNNING) { pendingTasks.set(pendingTasks.get() - 1); } })); tasks.forEach(exec::execute); }); VBox root = new VBox(10, pendingTasksLabel, progressBar, log, button); root.setAlignment(Pos.CENTER); root.setPadding(new Insets(10)); VBox.setVgrow(log, Priority.ALWAYS); primaryStage.setScene(new Scene(root, 400, 400)); primaryStage.show(); } @Override public void stop() { exec.shutdownNow() ; } private Task<Void> createRandomTask() { int numSteps = 100 + rng.nextInt(100); return new Task<Void>() { @Override public Void call() throws Exception { for (int i = 1; i <= numSteps; i++) { Thread.sleep(50); updateProgress(i, numSteps); } return null ; } }; } public static void main(String[] args) { launch(args); } }