Can I automatically generate controller classes from FXML?

Question

As I understand it, when using FXML to describe a Java FX scene, the controller class is written manually and it's member variables and methods can then be referenced from the .fxml file. When loading the scene using the FXMLLoader, member variables are set to the corresponding scene elements and methods are wired up to the corresponding events automatically. This works but is very cumbersome as changes need to be done in two places and any mistakes will only show up at runtime.

I've seen other GUI frameworks that allow you to instead generate the controller from a scene description as an abstract class which needs to be implemented to access the scene elements and handle the events. An example of what I mean:

I would create the following .fxml file (e.g. using the JavaFX Scene Builder):

<AnchorPane ... >
  <children>
     <Button fx:id="button" ... text="Button" onAction="#buttonPressed" />
  </children>
</AnchorPane>

Somewhere in my build process, the following .java file would be created (e.g. using a Maven plugin):

abstract class TestController {
    protected final Parent root;
    protected final Button button;

    {
        // Load test.fxml file
        // Assign scene elements to root and button
        // Attach event handler to the button that calls buttonClicked()
    }

    protected abstract void buttonClicked(ActionEvent event);
}

I could then, possibly multiple times, create a concrete implementation of that controller:

final class TestControllerImpl extends TestController {
    TestControllerImpl(String buttonLabel) {
        button.setText(buttonLabel);
    }

    @Override
    protected void buttonClicked(ActionEvent event) {
        button.setText("I've been clicked! What a great day!");
    }
}

Is there a project with the goal to do this? Or is there a problem with this approach applied to FXML?

I see the following benefits from this approach:

• Declarations for member variables and methods for the controller are automatically generated.
• All member variables are final and protected instead of non-final and either public or annotated.
• The same for methods, they are protected instead of either public or annotated.
• Not implementing a method or misspelling it's name will lead to a compiler error.
• Programmatic setup of the scene can be done in the constructor instead of an initialize() method because the constructor will run after the scene has been loaded and its elements assigned to the member variables.

Answer 1

Update Nov 2020

This answer is now outdated.

As various more recent answers have pointed out, there are now a variety of additional different tools available for automatically generating FXML controller classes from FXML documents. Many of these are targeted as extensions, features or plugins to existing development tools, such as SceneBuilder, Idea, Eclipse or NetBeans.

I suggest that interested readers review both this answer and other answers to this question, then look at their individual use-case and toolset chain and choose the solution which is most appropriate for them from the available choices.

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There is nothing I know that does exactly what you propose in your question.

Likely this answer will probably end up pretty outdated over time.

Alternate Technologies

JRuby achieves most of your outlined benefits using a slightly different approach - it uses jRuby's dynamic programming magic to automatically create Ruby class members from the FXML dynamically a runtime.

Tom Schindl wrote a tool which generates Java code from FXML. Of the approaches listed in this answer, Tom's tool seems closest to your question.

SceneBuilder Skeletons

A similar Java code generator from FXML is available in SceneBuilder View | Show Sample Controller Skeleton feature, which is described in this blog post. When I use SceneBuilder, I use this feature all the time and try to keep my controllers really light so they are almost all auto generated code from the SceneBuilder skeleton feature.

It is slightly annoying though because it doesn't achieve a clean separation of generated code from hand written code, so you need to be careful when you do updates to the FXML and want to generate a new skeleton and copy and paste it over parts of your existing Controller (plus that is a slightly error prone manual operation that takes a little bit of developer time).

Source code for SceneBuilder is available if you want to see how it works.

Potential Build Tool Plugins

Such a code generation feature might make a worthwhile addition to some of the existing build tools in the JavaFX ecosystem, such as the JavaFX Maven plugin or JavaFX Gradle plugin (or a separate plugin in it's own right).

Future Development

I believe that Oracle are also working on a feature extension for FXML for a future JavaFX release (post Java 8) which compiles FXML directly to Java byte code (class files), bypassing the Java source code step. This kind of feature would probably achieve most of your outlined benefits.

Answer 2

This is now supported in SceneBuilder, NetBeans and in Eclipse. Note this works out of the box in NetBeans and SceneBuilder, but in Eclipse you first need the e(fx)clipse plugin.

SceneBuilder: With an FXML file open in the editor, enter the menu to select "View" and "Show Sample Controller Skeleton".

Eclipse: Open the fxml file so the contents are displayed in the code editing pane (you should see the fxml as plaintext xml with syntax highlighting inside Eclipse, not rendered visually in SceneBuilder). Right-click on the code in Eclipse and select "Code" and then "Generate Controller".

NetBeans: In NetBeans it is even easier, right-click the fxml file in the project explorer and select "Make Controller".

Answer 3

It is possible with NetBeans version 8.

Open FXML , go to Source and click generate controller.

Edit: Now can be done in any IDE , Eclipse needs a plugin thought.

Answer 4

For Intellij Idea IDE users, FXMLManager to the rescue. See the plugin homepage

"When clicking right mouse button on .fxml file, there is new menu item "Update Controller from FXML". Clicking this item will modify FXML Java Controller:

• Remove all @FXML fields that are missing in FXML and their getters/setters
• Add all @FXML fields that are missing in Controller
• @Deprecate all ActionEvent methods that are missing in FXML
• Create all ActionEvent methods that are missing from Controller"

Answer 5

As I know, there are two kind of solutions exist in netbeans.

First, netbeans's internal feature "Make Controller", which you can see with right mouse click on the fxml document. it will generate controller class which will work with FXMLLoader. The controller's java file name should be indicated in the fxml document. (left panel -> Controller -> Controller class)

Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

Second, netbeans's plugin "FXML 2 JAVA Converter", which you can install from menu (Tool -> Plugin -> Available Plugin -> FXML 2 JAVA Converter). and you can see "Generate Abstract Class" menu item with right mouse click on the fxml document. It will generate source code from fxml document and you can use it as an abstract class without using FXMLLoader like normal JavaFX project not JavaFXML project.

Answer 6

Now you can easily do it with eclipse Just do these simple steps :

1. Go to your fxml file that you want to create Controller for
2. Right Click and Click source
3. Click Generate Controller

Click here to see the Picture of How to do it.

Answer 7

If you're using IntelliJ ide, you may have to try FXML Helper plugin.
First, install the plugin from the File | Settings... | Plugins. After the installation restart the ide, Now right click on the .fxml document and select the FXML Helper menu. That`s all.

Answer 8

@Feuermurmel
no there is not any ways to generate automatically controller class for particula .fxml file.
you should define dynamically declare variable and method with anotation @fxml and set(bind) in scence builder.