This tutorial illustrates the creation of a small application based on the NetBeans Rich Client Platform (RCP), and JavaFx, which will monitor the prices of a few stocks and update the UI in real time as prices are updated.  The application will make use of SceneBuilder to create an main UI, and JavaFX property bindings in order to keep the UI up to date as the prices are updated.

The Model

First, lets start with the model, a Stock class which will simply consist of a ticker symbol and a name.

public class Stock {
    
    protected String symbol;
    protected String name;

    public Stock(String symbol, String name) {
        this.symbol = symbol;
        this.name = name;
    }

    public String getSymbol() {
        return symbol;
    }

    public String getName() {
        return name;
    }    
}

Next, the listener interface that we will need to implement in order to get updates on the prices.  The priceUpdated() method will be invoked whenever a new price arrives for a stock.

public interface StockPriceUpdatedListener {

    public void priceUpdated( Stock stock, double price );
    
}

The model will consist of a collection of stocks, each of which will be mapped to a StringProperty.  When a new stock is added to the model, a new StringProperty will be created and mapped to the specified stock.  The model implements the StockPriceUpdatedListener interface.  When a new price is received, the StringProperty for that Stock will be looked up and updated.

Note that in the model below that you need to be on the main JavaFx thread when you update a property!  For the purposes of this application the stock prices are arriving from a non-ui thread, so updating the property needs to be wrapped in a Platform.runLater() call which will put the update on to the ui-thread.

import com.mvc.stock.price.Stock;
import com.mvc.stock.price.StockPriceUpdatedListener;
import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.Map;
import javafx.application.Platform;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;

public class StockModel implements StockPriceUpdatedListener {
    
    protected Map<Stock, StringProperty> stocks = new HashMap<>();
    DecimalFormat df = new DecimalFormat("$##0.00");
    
    public StringProperty addStock( Stock stock ) {
        StringProperty property = stocks.get(stock);
        if( property == null ) {
            property = new SimpleStringProperty("");
            stocks.put(stock, property);
        }
        
        return property;
    }
    
    @Override
    public void priceUpdated(Stock stock, double price) {
        //Don't update the properties from a non-JavaFx-UI thread!
        Platform.runLater( () -> stocks.get(stock).setValue(df.format(price)));
    }    
}

The View

Next, the view for this application was designed with SceneBuilder.  The layout consists of a GridPane containing information about a few stocks, as well as a subscribe button which will trigger the monitoring of price information.

SceneBuilder generated the following FXML code below, with the UI controller set to:

com.mvc.stock.ui.StockPriceController

Also note that the button has its onAction event defined to call the subscribeButtonClicked() method which will need to be implemented in the StockPriceController class.

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.text.*?>
<?import javafx.geometry.*?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>


<AnchorPane id="AnchorPane" prefHeight="197.0" prefWidth="233.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8" fx:controller="com.mvc.stock.ui.StockPricePanelController">
    <children>
        <GridPane alignment="CENTER" gridLinesVisible="true" layoutX="14.0" layoutY="14.0">
            <columnConstraints>
                <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
                <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            </columnConstraints>
            <rowConstraints>
                <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
                <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
                <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
                <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
            </rowConstraints>
            <children>
                <Label text="MSFT" GridPane.halignment="RIGHT" GridPane.rowIndex="1">
                    <padding>
                        <Insets right="10.0" />
                    </padding>
                </Label>
                <Label alignment="CENTER" text="Stock" textAlignment="CENTER" GridPane.halignment="CENTER">
                    <padding>
                        <Insets right="10.0" />
                    </padding>
                    <font>
                        <Font name="System Bold" size="13.0" />
                    </font>
                </Label>
                <Label text="Last Price" GridPane.columnIndex="1" GridPane.halignment="CENTER">
                    <font>
                        <Font name="System Bold" size="13.0" />
                    </font>
                </Label>
                <Label text="EBAY" GridPane.halignment="RIGHT" GridPane.rowIndex="3">
                    <padding>
                        <Insets right="10.0" />
                    </padding>
                </Label>
                <Label text="AMZN" GridPane.halignment="RIGHT" GridPane.rowIndex="2">
                    <padding>
                        <Insets right="10.0" />
                    </padding>
                </Label>
                <Label fx:id="msftPriceLabel" GridPane.columnIndex="1" GridPane.rowIndex="1">
                    <padding>
                        <Insets left="10.0" />
                    </padding>
                </Label>
                <Label fx:id="amznPriceLabel" GridPane.columnIndex="1" GridPane.rowIndex="2">
                    <padding>
                        <Insets left="10.0" />
                    </padding>
                </Label>
                <Label fx:id="ebayPriceLabel" GridPane.columnIndex="1" GridPane.rowIndex="3">
                    <padding>
                        <Insets left="10.0" />
                    </padding>
                </Label>
            </children>
        </GridPane>
        <Button fx:id="subscribeButton" layoutX="136.0" layoutY="153.0" mnemonicParsing="false" onAction="#subscribeButtonClicked" text="Subscribe" />
    </children>
</AnchorPane>

The Controller

As mentioned above, the FXML file references StockPricePanelController as the UI’s controller.  The controller has 3 labels and a button defined which will be injected into the controller by annotating those fields with the @FXML annotation.  When the controller is first initialized it creates a new stock object for each stock and then binds the StringProperty of the StockModel to the StringProperty of its corresponding label.

Also, as previously stated, the controller will need to implement a method called subscribeButtonClicked() which was defined in the FXML above.  This method needs to be annotated with the @FXML annotation in order to be invoked when the subscribeButton is clicked.  When this action is invoked, the controller will subscribe to price data for the specified stocks.

import com.mvc.stock.price.Stock;
import com.mvc.stock.price.provider.IStockPriceProvider;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Label;

/**
 * FXML Controller class
 *
 */
public class StockPricePanelController implements Initializable {

    
    @FXML
    protected Label msftPriceLabel;
    
    @FXML
    protected Label amznPriceLabel;
    
    @FXML
    protected Label ebayPriceLabel;
    
    @FXML
    protected Button subscribeButton;
    
    protected StockModel stockModel;
    
    protected IStockPriceProvider provider;
    protected Stock msft = new Stock("MSFT", "Microsoft");
    protected Stock amzn = new Stock("AMZN", "Amazon");
    protected Stock ebay = new Stock("EBAY", "eBay");
    
    
    /**
     * Initializes the controller class.
     */
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        stockModel = new StockModel();
        //bind the string property from the model to the labels.
        msftPriceLabel.textProperty().bindBidirectional( stockModel.addStock(msft) );
        amznPriceLabel.textProperty().bindBidirectional( stockModel.addStock(amzn) );
        ebayPriceLabel.textProperty().bindBidirectional( stockModel.addStock(ebay) );
    }    

    public IStockPriceProvider getProvider() {
        return provider;
    }

    public void setProvider(IStockPriceProvider provider) {
        this.provider = provider;
    }

    @FXML
    public void subscribeButtonClicked( ActionEvent event ) {
        if( provider != null ) {
            provider.subscribeToPriceData(msft, stockModel);
            provider.subscribeToPriceData(amzn, stockModel);
            provider.subscribeToPriceData(ebay, stockModel);
        }
    }
    
}

The final piece is to tie JavaFX UI into the NetBeans module which this component is a part of.  In order to do this you will need to have a TopComponent defined for your module like in the example below.  Basically a TopComponent is a top level panel that is usually within a TabbedPane in the main UI.  The TopComponent class below uses the Lookup API to find an implementation of an IStockPriceProvider interface.  Next a JFXPanel is created, which is a Swing JPanel that can hold a JavaFX Scene.

Within the Platform.runLater() method, a new FXMLLoader is created which points to the location of the FXML file from above.  Once the loader has loaded the file, we can obtain a reference to the StockPricePanelController, and pass in the instance of the stockPriceProvider that was previously just looked up.

Finally, a new Scene is created,  added to the JFXPanel, and the JFXPanel is added to the Center position of the TopComponent.

public final class StockPriceTopComponent extends TopComponent {

    public StockPriceTopComponent() {
        initComponents();
        setName(Bundle.CTL_StockPriceTopComponent());
        setToolTipText(Bundle.HINT_StockPriceTopComponent());
        putClientProperty(TopComponent.PROP_CLOSING_DISABLED, Boolean.TRUE);
        putClientProperty(TopComponent.PROP_DRAGGING_DISABLED, Boolean.TRUE);
        putClientProperty(TopComponent.PROP_UNDOCKING_DISABLED, Boolean.TRUE);
        
        
        IStockPriceProvider stockPriceProvider = Lookup.getDefault().lookup(IStockPriceProvider.class);
        if( stockPriceProvider == null ) {
            throw new IllegalStateException( "Provider is null");
        }        
        
        JFXPanel jfxPanel = new JFXPanel();

        //This needs to be set to make sure the JavaFx thread doesn't exit if the tab is closed.
        Platform.setImplicitExit(false);
        
        // create JavaFX scene
        Platform.runLater(() -> {
            Parent root;
            try {
                FXMLLoader loader = new FXMLLoader(getClass().getResource("/com/mvc/stock/ui/StockPricePanel.fxml"));
                root = loader.load();
                StockPricePanelController controller = loader.getController();
                controller.setProvider(stockPriceProvider);
                
                Scene scene = new Scene(root);
                
                jfxPanel.setScene(scene);
            } catch (IOException ex) {
                Exceptions.printStackTrace(ex);
            }
        });
        add( jfxPanel, BorderLayout.CENTER );
    }

The resulting NetBeans application is shown below.

twitter: @RobTerpilowski
twitter: @LimitUpTrading

I have a fair amount of pluggable infrastructure in place with the NetBeans platform for trading related applications. My latest application, “Atlas Trader” is being used to route our commodity trades through Quantitative Brokers. I want to take advantage of JavaFX for this project as it provides a cleaner MVC separation than Swing does, and also provides a lot of eye candy out of the box, such as animated transitions, translucency, etc.). I have been having strange issues however when attempting to incorporate this as a module to my NetBeans platform application.

I started out with a stripped down version of the platform, since I don’t need any of the Swing components and all the UI components with be within an JavaFX Scene, so have only included the following RCP modules:

• org-netbeans-api-annotations-common
• org-openide-modules
• org-openide-util
• org-openide-util-lookup

In my module’s “Installer” class, the restored() method kicks off the JavaFX app with the following calls:

Application.launch(MainApp.class);
Platform.setImplicitExit(false);

All seems to be ok at this point. The app launches and displays the UI correctly. I can log in and get to the main screen of the application.

Below is the main screen in the application. The issues arrises when one of the commodity labels at the top of the screen is clicked. The expected behaviour is to display a new JavaFX componenet allowing the user to enter an order.

The “CommodityHeaderLabels” at the top of the UI have the following action method defined.

@FXML
public void fireCommodityClicked() {

When one of these headers are clicked, an exception is immediately thrown, complaining that:

Caused by: javafx.fxml.LoadException: 

/Users/RobTerpilowski/ZoiCapital/JavaSource/QTrader/ZQTrader-Plugin/target/classes/com/zoicapital/qtrader/plugin/TradePanel.fxml:15

at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2605)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2583)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2445)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2413)
at com.zoicapital.qtrader.plugin.TradePanel.init(TradePanel.java:198)
... 10 more

Caused by: java.lang.NullPointerException
at javafx.fxml.FXMLLoader.loadTypeForPackage(FXMLLoader.java:2920)

After drilling into the FXMLLoader class to find out what was going on, it appears that the “fireCommodityClick()” method is not being called from the JavaFX Event thread, and so it isn’t able to load the FXML file for the component that it needs to create when the item is clicked.

In fact, when running through the debugger, the JavaFX Thread is running prior to the component being clicked, but disappears when the component is clicked.

To make things even more difficult to understand, is that all the events leading up to this point are executed as expected in the RCP version of this application on the Java FX Application Thread. As I mentioned, I can log in to the application without any issues, and its not until one of these CommodityLabel components are clicked that the issue appears. Below is a screenshot of NB in the debugger with a breakpoint at the first line in the method that is called when the component is clicked. On the left side of the screen you can see the stack trace and that the current thread is the “AppKit Thread”, with the Java FX Application thread no longer present.

I set up a test project to run this application as a stand-alone outside of the NetBeans RCP, and things work as expected. The event method is called on the JavaFX Application Thread, and the resulting component is created and displayed as expected.

I can only think that there is an exception being swallowed somewhere, and that there may possibly be another NetBeans Platform module that is required in addition to the 4 modules that I mentioned at the beginning of this post.

I realize this post is a little short on the amount of code, but I’m looking for any other ideas on areas I could look at to further debug this issue.

twitter: @RobTerpilowski