Styjun

I am making two simple JMS application with JavaFx (one for sender and the other one is receiver).

But, I could not refresh the GUI of the receiver with the new arriving message from the sender.

From debugging, I noticed that the receiver received the message from the server, but the receiver could not add it to my ObservableList (which, of course, resulted in no refreshing in the GUI of the ListView).

I looked up on the internet with onMessage event, and override it (to add an item to the ObservableList there), but it is not working. After the event is raised, no element was added to the ObservableList.

This is my receiver:

public class Administrator extends Application 
 private ObservableList<String> observableList;
 private final String DESTINATION_TYPE = "queue";
 private final String RECEIVE_CHANNEL = "askDestination";
 private final String SEND_CHANNEL = "answerDestination";
 private MessageConsumer messageConsumer;
 private MessageProducer messageProducer;
 private Session session;
 private Destination destination;
 private Connection connection;

 @FXML
 public TextField tfMessage;

 @FXML
 public ListView<String> lvMessage;

 @FXML
 public Button btnSend;

 @Override
 public void start(Stage stage) throws IOException 
 Parent root = FXMLLoader.load(getClass().getResource("administratorUI.fxml"));
 stage.setTitle("Administrator");
 stage.setScene(new Scene(root, 640, 480));
 stage.setResizable(false);
 stage.show();
 

 @Override
 public void init() throws Exception 
 super.init();
 lvMessage = new ListView<>();
 tfMessage = new TextField();
 //questionList = new ArrayList<>();
 observableList = FXCollections.observableArrayList();
 lvMessage.setItems(observableList);
 initService(RECEIVE_CHANNEL, DESTINATION_TYPE);
 getMessage(RECEIVE_CHANNEL);
 //Platform.runLater(this::updateLV);
 

 public static void main(String[] args) 
 launch();
 

 public void onButtonAnswerClick() 
 String message = tfMessage.getText();

 if (message.equals("")) 
 Alert alert = new Alert(Alert.AlertType.ERROR);
 alert.setContentText("Please enter your message!!");
 alert.show();
 return;
 

 if (replyToQuestion(message, SEND_CHANNEL)) 
 tfMessage.clear();
 else 
 handleServiceError("Service Error", "Could not send the message to the service");
 
 

 private void handleServiceError(String errorTitle, String errorText)
 Alert error = new Alert(Alert.AlertType.ERROR);
 error.setTitle(errorTitle);
 error.setContentText(errorText);
 

 private void updateLV()
 lvMessage.getItems().clear();
 lvMessage.setItems(observableList);
 

 private void initService(String targetDestination, String destinationType) JMSException e) 
 e.printStackTrace();
 
 

 private boolean replyToQuestion(String message, String sendDestination) 
 try 
 initService(sendDestination, DESTINATION_TYPE);

 // for sending messages
 messageProducer = session.createProducer(destination);

 // create a text message
 Message msg = session.createTextMessage(message);

 msg.setJMSMessageID("222");
 System.out.println(msg.getJMSMessageID());

 // send the message
 messageProducer.send(msg);

 //questionList.add(message);
 updateLV();
 return true;
 catch (JMSException e) 
 e.printStackTrace();
 return false;
 
 

 private void getMessage(String receiveDestination) 
 try 
 initService(receiveDestination, DESTINATION_TYPE);

 // this is needed to start receiving messages
 connection.start();

 // for receiving messages
 messageConsumer = session.createConsumer(destination);
 MessageListener listener = message -> 
 try 
 observableList.add(((TextMessage)message).getText());
 catch (JMSException e) 
 e.printStackTrace();
 
 ;

 messageConsumer.setMessageListener(listener);
 catch (JMSException e) 
 e.printStackTrace();
 
 

And my sender:

 public class User extends Application implements MessageListener 
 private static List<String> questions;
 private final String DESTINATION_TYPE = "queue";
 private final String RECEIVE_CHANNEL = "answerDestination";
 private final String SEND_CHANNEL = "askDestination";
 private String requestId;
 private MessageConsumer messageConsumer;
 private MessageProducer messageProducer;
 private Session session;
 private Destination destination;
 private Connection connection;

 @FXML
 public Button btnSend;

 @FXML
 public TextField tfMessage;

 @FXML
 public ListView lvMessage;

 @Override
 public void start(Stage stage) throws IOException 
 Parent root = FXMLLoader.load(getClass().getResource("userUI.fxml"));
 stage.setTitle("Sender");
 stage.setScene(new Scene(root, 640, 480));
 stage.setResizable(false);
 stage.show();
 

 @Override
 public void init() throws Exception 
 super.init();
 btnSend = new Button();
 tfMessage = new TextField();
 lvMessage = new ListView();
 questions = new ArrayList<>();
 initService(RECEIVE_CHANNEL, DESTINATION_TYPE);
 getAnswer(RECEIVE_CHANNEL);
 

 public static void main(String[] args)
 launch(args);
 

 public void onButtonSendClick(javafx.event.ActionEvent actionEvent) 
 String message = tfMessage.getText();

 if (message.equals("")) 
 Alert alert = new Alert(Alert.AlertType.ERROR);
 alert.setContentText("Please enter your question!!");
 alert.show();
 return;
 

 if (sendQuestion(message, SEND_CHANNEL)) 
 tfMessage.clear();
 else 
 handleServiceError("Service Error", "Could not send the message tot the service");
 
 

 private void handleServiceError(String errorTitle, String errorText)
 Alert error = new Alert(Alert.AlertType.ERROR);
 error.setTitle(errorTitle);
 error.setContentText(errorText);
 

 private void updateLV()
 lvMessage.getItems().clear();
 lvMessage.getItems().addAll(questions);
 

 private void initService(String targetDestination, String destinationType)
 try 
 Properties props = new Properties();
 props.setProperty(Context.INITIAL_CONTEXT_FACTORY,
 "org.apache.activemq.jndi.ActiveMQInitialContextFactory");
 props.setProperty(Context.PROVIDER_URL, "tcp://localhost:61616");

 // connect to the Destination called “myFirstChannel”
 // queue or topic: “queue.myFirstDestination” or “topic.myFirstDestination”
 props.put((destinationType + "." + targetDestination), targetDestination);
 Context jndiContext = new InitialContext(props);
 ConnectionFactory connectionFactory = (ConnectionFactory) jndiContext.lookup("ConnectionFactory");

 // to connect to the JMS
 connection = connectionFactory.createConnection();
 // session for creating consumers
 session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);

 // connect to the receiver destination
 //reference to a queue/topic destination
 destination = (Destination) jndiContext.lookup(targetDestination);
 catch (NamingException 

 private boolean sendQuestion(String message, String sendDestination) 
 try 
 initService(sendDestination, DESTINATION_TYPE);

 // for sending messages
 messageProducer = session.createProducer(destination);

 // create a text message
 Message msg = session.createTextMessage(message);

 msg.setJMSMessageID("111");
 System.out.println(msg.getJMSMessageID());

 // send the message
 messageProducer.send(msg);

 //questionList.add(message);
 updateLV();
 return true;
 catch (JMSException e) 
 e.printStackTrace();
 return false;
 
 

 private void getAnswer(String receiveDestination) 
 try 
 initService(receiveDestination, DESTINATION_TYPE);

 // for receiving messages
 messageConsumer = session.createConsumer(destination);
 messageConsumer.setMessageListener(this);


 // this is needed to start receiving messages
 connection.start();
 catch (JMSException e) 
 e.printStackTrace();
 
 

 @Override
 public void onMessage(Message message) 
 try 
 questions.add(((TextMessage)message).getText());
 requestId = message.getJMSMessageID();
 System.out.println(requestId);
 updateLV();
 catch (JMSException e) 
 e.printStackTrace();
 
 

The FXML of the receiver:

 <GridPane hgap="10" prefHeight="400.0" prefWidth="600.0" vgap="10" xmlns="http://javafx.com/javafx/8.0.172-ea" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Administrator">
 <padding>
 <Insets bottom="10" left="10" right="10" top="10" />
 </padding>
 <Label text="Current question:" textFill="cornflowerblue" GridPane.columnIndex="0" GridPane.rowIndex="0">
 <font>
 <Font name="System Bold" size="15.0" />
 </font>
 </Label>
 <ListView fx:id="lvMessage" prefWidth="600" GridPane.columnIndex="0" GridPane.columnSpan="2" GridPane.rowIndex="1">

 </ListView>

 <HBox spacing="10" GridPane.columnIndex="0" GridPane.columnSpan="2" GridPane.rowIndex="2">
 <TextField fx:id="tfMessage" prefHeight="61.0" prefWidth="504.0" promptText="Type your answer here...">
 <font>
 <Font size="15.0" />
 </font>
 </TextField>
 <Button fx:id="btnSend" onAction="#onButtonAnswerClick" prefHeight="61.0" prefWidth="88.0" text="Send">
 </Button>
 </HBox>
 <columnConstraints>
 <ColumnConstraints />
 <ColumnConstraints />
 </columnConstraints>
 <rowConstraints>
 <RowConstraints />
 <RowConstraints />
 <RowConstraints />
 </rowConstraints>
</GridPane>

After the receiver received the message, the event is raised so I expected the ListView to be updated with the new message. However, no element was added to the ObservableList => no update in the ListView.

So, I would like to ask if what I did is wrong or correct?

Turn out that I was updating the ListView on the wrong thread. For those who is still interesting in the answer, I used: Platform.runLater() and registered the event listener in the start method (before stage.show())