I am creating a Javafx chat app which also allows for file transfer. My issue is I open a FileOutputStream for the received file within the below method. I can see my listener.statusTransferring() updating the UI only if I enable Platform.runLater. I think I now need to enable the same on the fos.write(b, 0, tmpTransferred) within the while loop but don't know how to do this. I have tried unsuccessfully wrapping the whole method within Platform runlater. Note: If I don't use platform runlater I don't get any errors however the UI does not update until the file transfer is complete eg listener.statusCompleted() is called;. The error I get now as a result of the fos being in Platform runlater. is below.. Line 185 is fos.write(b, 0, tmpTransferred); The other listener calls appear to work fine. Just not listener.statusTransferring(); or listener.transferUpdate(); which utilise the fos. Any help will be greatly appreciated. Also for your own sanity I am a self taught google programmer. Yep the worst kind I am sure. Thanks in advance.
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at net.thebowdens.net.FileReceiver.transfer(FileReceiver.java:185)
at net.thebowdens.net.DefaultMessageResponder.fileSend(DefaultMessageResponder.java:543)
public boolean transfer() {
listener.statusConnecting();
received = false;
cancel = false;
try {
if (sSock != null) {
sock = sSock.accept();
listener.statusTransferring();
Platform.runLater(() ->{
try {
fos = new FileOutputStream(file);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
});
is = sock.getInputStream();
final byte[] b = new byte[1024];
transferred = 0;
percent = 0;
int tmpTransferred = 0;
int tmpPercent = 0;
int transCounter = 0;
bCounter.prepare();
while (!cancel && (tmpTransferred = is.read(b)) != -1) {
fos.write(b, 0, tmpTransferred);
transferred += tmpTransferred;
percent = (int) ((transferred * 100) / size);
bCounter.addBytes(tmpTransferred);
transCounter++;
if (percent > tmpPercent || transCounter >= 250) {
transCounter = 0;
tmpPercent = percent;
listener.transferUpdate();
}
}
if (!cancel && transferred == size) {
received = true;
listener.statusCompleted();
}
else {
listener.statusFailed();
}
}
}
catch (final IOException e) {
LOG.log(Level.SEVERE, e.toString());
listener.statusFailed();
}
finally {
stopReceiver();
cleanupConnections();
}
return received;
}
Keep in mind that you should use Platform.runLater only for updating the UI, everything else should be outside it otherwhise the UI will become unresponsive.
I suggest you to to refactor your code according to this.
Well after much discussion over the correct language and other issues I solved my problem of the UI updating. I had two issues. My choice selector and Filechooser methods were not on the Javafx application thread (hope this is the right terminology) so I had to do the following:
private ExecutorService executorService = Executors.newCachedThreadPool();
executorService.execute(new Runnable() {
#Override
public void run() {
Platform.runLater(() -> {
try {
receiveRequest(tmpUser, fileRes, user, fileName, size, fileHash);
} catch (IOException | ServerException | CommandException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
});
}
});
I then had to do the same within the Filechooser and file accept method for the transfer class UI to update
executorService.execute(new Runnable() {
#Override public void run() {
if (fileRes.transfer()) {
ui.showSystemMessage("Successfully received " + fileName +
" from " + user + ", and saved as " + fileRes.getFile().getName());
}
else {
ui.showSystemMessage("Failed to receive " + fileName + " from " + user);
fileRes.cancel();
}
}
});
}
Related
... that is after all its properties - including its value - are updated?
The use-case is a Task that
"collects" items into an ObservableList which is the result of the call method
the list should be set as value when the task is "finished", no matter if normally or cancelled
A snippet of the Task implementation (complete example at end):
#Override
protected ObservableList<Rectangle> call() throws Exception {
ObservableList<Rectangle> results = FXCollections.observableArrayList();
for (int i=0; i<=count; i++) {
// do fill list
//...
try {
Thread.sleep(200);
} catch (InterruptedException interrupted) {
if (isCancelled()) {
// do update value on cancelled
updateValue(results);
break;
}
}
}
return results;
}
It's intended usage:
bind the itemsProperty of a tableView to the valueProperty
unbind on "finished"
My approach was to listen to its state property and unbind on state changes to SUCCEEDED or CANCELLED. The former works just fine, the latter doesn't because at the time of receiving the cancelled, the value is not yet updated and consequently the items not set.
// working ... but when to unbind?
table.itemsProperty().bind(task.valueProperty());
task.stateProperty().addListener((src, ov, nv) -> {
if (Worker.State.SUCCEEDED == nv ) {
// this is fine because implementation in TaskCallable first
// updates the value (with the result it got from T call())
// then updates state
LOG.info("succeeded" + task.getValue());
table.itemsProperty().unbind();
} else if (Worker.State.CANCELLED == nv) {
LOG.info("receiving cancelled " + task.getValue());
// can't unbind here, value not yet updated
// table.itemsProperty().unbind();
}
});
So in case of cancelled, this leaves me with either a property that's still bound or an empty table. Feels like I'm doing something wrong. Or core Task impl is not as useful as expected? It would mean that we simply can't bind to the value property (nor any of the others like progress) due to being unable to safely cleanup (using table items here is just an example, because it's easy to see, same for all types of properties).
Question is, how to do it correctly/overcome the limitation?
The complete example:
public class TaskValueBinding extends Application {
private Parent createListPane() {
Task<ObservableList<Rectangle>> task = createListTask();
Thread thread = new Thread(task);
thread.setDaemon(true);
TableView<Rectangle> table = new TableView<>();
TableColumn<Rectangle, Double> xCol = new TableColumn<>("X");
xCol.setCellValueFactory(new PropertyValueFactory<>("x"));
TableColumn<Rectangle, Double> yCol = new TableColumn<>("Y");
yCol.setCellValueFactory(new PropertyValueFactory<>("y"));
table.getColumns().addAll(xCol, yCol);
// working ... but when to unbind?
table.itemsProperty().bind(task.valueProperty());
task.stateProperty().addListener((src, ov, nv) -> {
if (Worker.State.SUCCEEDED == nv ) {
// this is fine because implementation in TaskCallable first
// updates the value (with the result it got from T call())
// then updates state
LOG.info("succeeded" + task.getValue());
table.itemsProperty().unbind();
} else if (Worker.State.CANCELLED == nv) {
LOG.info("receiving cancelled " + task.getValue());
// can't unbind here, value not yet updated
// table.itemsProperty().unbind();
}
});
Label messageLabel = new Label("Message: ");
Label message = new Label();
message.textProperty().bind(task.messageProperty());
Label progressAsText = new Label();
Label progressLabel = new Label("Progress: ");
progressAsText.textProperty().bind(task.progressProperty().asString());
ProgressBar progress = new ProgressBar();
progress.progressProperty().bind(task.progressProperty());
Button start = new Button("Start");
start.setOnAction(e -> {
start.setDisable(true);
thread.start();
});
Button cancel = new Button("Cancel");
cancel.setOnAction(e -> task.cancel());
cancel.disableProperty().bind(task.runningProperty().not());
int row = 0;
GridPane grid = new GridPane();
grid.add(table, 0, row++, 20, 1);
grid.add(messageLabel, 0, row);
grid.add(message, 1, row++);
grid.add(progressLabel, 0, row);
grid.add(progressAsText, 1, row++);
grid.add(progress, 0, row++, 2, 1);
grid.add(start, 0, row);
grid.add(cancel, 1, row++);
return grid;
}
private Task<ObservableList<Rectangle>> createListTask() {
Task<ObservableList<Rectangle>> task = new Task<ObservableList<Rectangle>>() {
#Override
protected ObservableList<Rectangle> call() throws Exception {
updateMessage("Creating Rectangles ...");
ObservableList<Rectangle> results = FXCollections.observableArrayList();
String message = "finished";
int count = 10;
for (int i=0; i<=count; i++) {
if (isCancelled()) {
updateValue(results);
// when do we get here?
message = "cancelled";
break;
}
Rectangle r = new Rectangle(10, 10);
r.setX(10 * i);
results.add(r);
updateProgress(i, count);
// Now block the thread for a short time, but be sure
// to check the interrupted exception for cancellation!
try {
Thread.sleep(200);
} catch (InterruptedException interrupted) {
if (isCancelled()) {
updateValue(results);
message = "interrupted";
break;
}
}
}
updateMessage(message);
return results;
}
};
return task;
}
#Override
public void start(Stage stage) throws Exception {
stage.setScene(new Scene(createListPane()));
stage.setTitle(FXUtils.version());
stage.show();
}
public static void main(String[] args) {
launch(args);
}
#SuppressWarnings("unused")
private static final Logger LOG = Logger
.getLogger(TaskValueBinding.class.getName());
}
Cancelling the task immediately triggers an update of the state property. If canceled from the application thread Platfrom.runLater is not used for this purpose but the call of the cancel method updates the state immediately. This results in the state being changed before any updateValue call updates the value property using Platform.runLater.
Task is not designed to allow partial results so you need to implement custom logic to accommodate for this. Depending on your needs you could subclass Task to trigger a custom event when the task completes in any way.
public abstract class PartialResultTask<T> extends Task<T> {
// handler triggered after last change of value
private Runnable onDone;
public Runnable getOnDone() {
return onDone;
}
public void setOnDone(Runnable onDone) {
this.onDone = onDone;
}
protected abstract T calculateResult() throws Exception;
private void onDone() {
if (onDone != null) {
Platform.runLater(onDone);
}
}
#Override
protected final T call() throws Exception {
try {
T result = calculateResult();
updateValue(result); // update value to the final value
onDone();
return result;
} catch (Exception ex) {
onDone();
throw ex;
}
}
}
private PartialResultTask<ObservableList<Rectangle>> createListTask() {
PartialResultTask<ObservableList<Rectangle>> task = new PartialResultTask<ObservableList<Rectangle>>() {
#Override
protected ObservableList<Rectangle> calculateResult() throws Exception {updateMessage("Creating Rectangles ...");
ObservableList<Rectangle> results = FXCollections.observableArrayList();
int count = 10;
for (int i = 0; !isCancelled() && i <= count; i++) {
Rectangle r = new Rectangle(10, 10);
r.setX(10 * i);
results.add(r);
updateProgress(i, count);
// Now block the thread for a short time, but be sure
// to check the interrupted exception for cancellation!
try {
Thread.sleep(200);
} catch (InterruptedException interrupted) {
}
}
updateMessage(isCancelled() ? "canceled" : "finished");
return results;
}
};
return task;
}
task.setOnDone(() -> {
table.itemsProperty().unbind();
});
task.stateProperty().addListener((src, ov, nv) -> {
if (Worker.State.SUCCEEDED == nv) {
// this is fine because implementation in TaskCallable first
// updates the value (with the result it got from T call())
// then updates state
LOG.info("succeeded" + task.getValue());
} else if (Worker.State.CANCELLED == nv) {
LOG.info("receiving cancelled " + task.getValue());
}
});
I am receiving strings from my server that I want to append into a Textarea on the client side (Think chat window). Problem is, when I receive the string, the client freezes.
insertUserNameButton.setOnAction((event) -> {
userName=userNameField.getText();
try {
connect();
} catch (IOException e) {
e.printStackTrace();
}
});
public Client() {
userInput.setOnAction((event) -> {
out.println(userInput.getText());
userInput.setText("");
});
}
private void connect() throws IOException {
String serverAddress = hostName;
Socket socket = new Socket(serverAddress, portNumber);
in = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(), true);
while (true) {
String line = in.readLine();
if (line.startsWith("SUBMITNAME")) {
out.println(userName);
} else if (line.startsWith("MESSAGE")) {
Platform.runLater(()->serverOutput.appendText(line.substring(8) + "\n"));
} else if (line.startsWith("QUESTION")) {
Platform.runLater(()->serverOutput.appendText(line.substring(8) + "\n"));
} else if (line.startsWith("CORRECTANSWER")) {
Platform.runLater(()->serverOutput.appendText(line.substring(14) + "\n"));
}
}
}
public static void main(String[] args) {
launch(args);
}
I have done some research and it seems that using Platform.runLater on each append should fix the problem. It doesn't for me.
Anyone has an idea of what it can be caused by? Thank you!
You are calling connect() on the FX Application Thread. Since it blocks indefinitely via the
while(true) {
String line = in.readLine();
// ...
}
construct, you block the FX Application Thread and prevent it from doing any of its usual work (rendering the UI, responding to user events, etc).
You need to run this on a background thread. It's best to use a Executor to manage the threads:
private final Executor exec = Executors.newCachedThreadPool(runnable -> {
Thread t = new Thread(runnable);
t.setDaemon(true);
return t ;
});
and then do
insertUserNameButton.setOnAction((event) -> {
userName=userNameField.getText();
exec.execute(() -> {
try {
connect();
} catch (IOException e) {
e.printStackTrace();
}
});
});
i have a very large database of images from the web which i am categorizing (downloaded locally).
so i have a website (locally) to do this, but the db queries were taking long, so i got an idea to "preload" the next page, so that only the very first load of the page would be slow. I save the list of items loaded in a seperate thread in session. So far so good.
I wanted to optimize further, and did some testing on what took the longest, and loading the images to check the size to see if i needed to scale them (set image height and width on the img obj) - so i wanted to do this with a parallel.foreach loop - but after doing this, my buttons on the page stopped responding? i can see the page runs through the page_load event when i press a button, but it doesn't reach the buttons "code":
protected virtual void btnSaveFollowPosts_Click(object sender, EventArgs e)
{...}
any take on what i am doing wrong? i have tried to limit the degree of paralellelism to 1 just to see if that would fix it - but it did not.
Update - code:
trying to boil it down:
protected void Page_Load(object sender, EventArgs e)
{
Search(false);
}
protected void Search(bool updateCounters)
{
if (Session[SessionItems] == null)
{
if (Session[SessionItemsCache] == null)
{
//if is being constructed, wait, else construct
//if construction is not running
if (Session[SessionCacheConstructionRunning] == null)
{
StartPreLoadContent();
}
while (Session[SessionCacheConstructionRunning] != null)
{
Thread.Sleep(25); //block main thread untill items ready
}
}
List<ContentView> contentViewList = Session[SessionItemsCache] as List<ContentView>;
Session[SessionItemsCache] = null; //clean preload cache
Session[SessionItems] = contentViewList; //save in current usage storage
Filltable(ref tblContent, contentViewList);
//preload next batch
StartPreLoadContent();
}
else
{
List<ContentView> contentViewList = Session[SessionItems] as List<ContentView>; //get items from session
Session[SessionItems] = contentViewList; //save in current usage storage
Filltable(ref tblContent, contentViewList);
}
}
protected void StartPreLoadContent()
{
Session[SessionCacheConstructionRunning] = true;
//start task
Thread obj = new Thread(new ThreadStart(RunPreLoadContent));
obj.IsBackground = true;
obj.Start();
}
protected void RunPreLoadContent()
{
using (DBEntities entities = new DBEntities())
{
entities.CommandTimeout = 86400;
IQueryable<ContentView> query = entities.ContentView.Where(some criterias);
List<ContentView> contentViewListCache = query.ToList();
ParallelOptions options = new ParallelOptions();
options.MaxDegreeOfParallelism = 7;
Parallel.ForEach(contentViewListCache, options, content =>
{
try
{
Interlocked.Increment(ref imageSizeCount);
string path = Path.Combine(basePath, content.LocalPath);
int imageSize = 150;
using (System.Drawing.Image realImage = System.Drawing.Image.FromFile(path))
{
double scale = 0;
if (realImage.Height > realImage.Width)
{
scale = (double)realImage.Height / imageSize;
}
else
{
scale = (double)realImage.Width / imageSize;
}
if (scale > 1)
{
content.ImageHeight = (int)((double)realImage.Height / scale);
content.ImageWidth = (int)((double)realImage.Width / scale);
content.ImageScaled = true;
}
content.ShowImage = true;
}
}
catch (Exception)
{
}
});
Session[SessionItemsCache] = contentViewListCache;
Session[SessionCacheConstructionRunning] = null; //cache ready
}
protected virtual void btnSave_Click(object sender, EventArgs e)
{
try
{
//save
...some reading and saving going on here...
//update
Session[SessionItems] = null;
Search(true);
}
catch (Exception error)
{
ShowError(error);
}
}
I agree with a previous comment: you should probably do this logic earlier in the page lifecycle. Consider overriding OnInit and putting it there.
Also, you could try this line of code instead of your current thread code (which is more suited to Windows not Web programming):
using System.Threading.Tasks;
Task.Run(() => { RunPreLoadContent(); });
Can anybody help telling me what is wrong with my code? I am trying to connect to SQLite database, and executing some queries. when trying to create and open the database, create and insert the table, no exception returned. but when I try to execute delete statement,
DatabaseIOException: File system error (12)
always returned. I don't know the cause of the exception exactly. would you tell me what usually cause this kind of exception? I don't even know when I need to close the database and when I don't need to. this solution also makes me confused.
here is my code:
public class DatabaseManager {
Logger log = new Logger();
Database db;
public DatabaseManager() {
createDatabase();
}
private void createDatabase() {
// Determine if an SDCard is present
boolean sdCardPresent = false;
String root = null;
Enumeration enum = FileSystemRegistry.listRoots();
while (enum.hasMoreElements()) {
root = (String) enum.nextElement();
if(root.equalsIgnoreCase("sdcard/")) {
sdCardPresent = true;
}
}
if(!sdCardPresent) {
alert("This application requires an SD card to be present. Exiting application...");
}
else {
try {
URI uri = URI.create("/SDCard/databases/MyAdvanceUI/myadvanceui.db");
db = DatabaseFactory.openOrCreate(uri);
db.close();
//alert("Database OK!");
} catch (Exception e) {
// TODO Auto-generated catch block
//alert("Exception in createDatabase(): " + e);
}
}
}
private void alert(final String message) {
UiApplication.getUiApplication().invokeLater(new Runnable() {
public void run() {
Dialog.inform(message);
System.exit(0);
}
});
}
private void createTableTask() {
try {
URI uri = URI.create("/SDCard/databases/MyAdvanceUI/myadvanceui.db");
db = DatabaseFactory.open(uri);
Statement st = db.createStatement("CREATE TABLE IF NOT EXISTS t_task (id INTEGER PRIMARY KEY AUTOINCREMENT, "
+ "client TEXT, task TEXT)");
st.prepare();
st.execute();
st.close();
db.close();
//alert("Table Task created!");
} catch (Exception e) {
// TODO: handle exception
//alert("Exception in createTableTask(): " + e);
}
}
private void insertTableTask() {
String[] clients = { "Budi Setiawan", "Dian Kusuma", "Joko Ahmad", "Titi Haryanto", "Wahyu" };
String[] tasks = {
"Penawaran terhadap instalasi server",
"Follow up untuk keperluan produk terbaru",
"Pendekatan untuk membina relasi",
"Penawaran jasa maintenance",
"Penawaran terhadap instalasi database"
};
try {
URI uri = URI.create("/SDCard/databases/MyAdvanceUI/myadvanceui.db");
db = DatabaseFactory.open(uri);
for(int i = 0; i < clients.length; i++) {
Statement st = db.createStatement("INSERT INTO t_task (client, task) VALUES (?, ?)");
st.prepare();
st.bind(1, clients[i]);
st.bind(2, tasks[i]);
st.execute();
st.close();
}
db.close();
} catch (Exception e) {
// TODO: handle exception
//alert("Exception in insertTableTask(): " + e);
}
}
public void loadInitialData() {
createTableTask();
insertTableTask();
}
public Cursor getTasks() {
// TODO Auto-generated method stub
Cursor results = null;
try {
URI uri = URI.create("/SDCard/databases/MyAdvanceUI/myadvanceui.db");
db = DatabaseFactory.open(uri);
Statement st = db.createStatement("SELECT client, task FROM t_task");
st.prepare();
results = st.getCursor();
return results;
} catch (Exception e) {
// TODO: handle exception
//alert("Exception: " + e);
}
return results;
}
public void delete(String string) {
// TODO Auto-generated method stub
try {
URI uri = URI.create("/SDCard/databases/MyAdvanceUI/myadvanceui.db");
db = DatabaseFactory.open(uri);
Statement st = db.createStatement("DELETE FROM t_task WHERE client=?");
st.prepare();
st.bind(1, string);
st.execute();
} catch (Exception e) {
// TODO: handle exception
alert("Exception: " + e);
}
}
}
thank you for your help.
I don't see that you close the statement and close the database after select and delete actions. Most probably you can't open database because it wasn't closed correctly.
Big warning SD card isn't available when user mounted devices to PC as external drive. Some devices are going without SD card preinstalled. DB operations are really slow on 5 OS devices. Your alert method code wan't close db what could be issue to open it after on the next application start.
Warning As #pankar mentioned in comment you should add finally {} where you will close resources for sure. In your current implementation if you get exception in execution you will never close database.
Big improvements You don't need to create and prepare statement every loop. Just do it before for. Do bind and execute every loop. And close statement after for.
Improvements You could keep one opened db during application run cycle. It will save you some line of code and time for opening closing.
Notation It's bad practice to have parameter named like 'string'. I would rename it to something more meaningful.
I'm currently having an issue with stopping a background thread in a webachive. I currently tie it in the war's deployment, and destroy it when the archive is un-deployed.
The threads starts up without issue, but when I close the archive, It seems to lose the handle on the thread. In the below case: st is null when the contextDestroyed method is called.
This is an issue as Tomcat notes the thread as orphaned in its warning about memory leaks.
public class LimitOrderContextListener implements ServletContextListener {
static Logger logger = Logger.getLogger(LimitOrderRuntime.class.getName());
private SwiftThread st = null;
/**
* Initializes this listener when this war's context is initialized
*/
public void contextInitialized(ServletContextEvent sce)
{
try {
if ( (st == null) || (!st.isAlive()) ) {
LimitOrderRuntime lor = new LimitOrderRuntime();
SwiftThread st = new SwiftThread(lor);
st.start();
} else {
st.gracefulStop();
st.join(2000);
}
} catch(Exception e) {
logger.warn("Unable to properly load thread! " +
e.getMessage() + " --cause " + e.getCause());
e.printStackTrace();
}
}
/**
* When this war is destroyed/stopped, stop the thread.
*/
public void contextDestroyed(ServletContextEvent sce)
{
try {
boolean success = st.gracefulStop();
if (!success) {
st.interrupt();
}
} catch (Exception e) {
logger.warn("Unable to properly release thread! " +
e.getMessage() + " --cause " + e.getCause());
e.printStackTrace();
}
}
}
In your contextInitialized method, you're redeclaring st as a local variable, rather than initializing the instance variable with the thread.
Replace
SwiftThread st = new SwiftThread(lor);
with
this.st = new SwiftThread(lor);