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https://github.com/manuel-mauky/fluxfx

Flux architecture with JavaFX
https://github.com/manuel-mauky/fluxfx

flux javafx javafx-library

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Flux architecture with JavaFX

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# FluxFX - Flux architecture with JavaFX



This is an experimental implementation of the [Flux Architecture](https://facebook.github.io/flux/docs/overview.html) with JavaFX.

"Experimental" means that the API is likely to be changed in the future and it's not production ready (yet) in terms of tests, documentation and feature set.

If you are looking for a production ready application framework for JavaFX have look at [mvvmFX](https://github.com/sialcasa/mvvmFX).



[![Build Status](https://travis-ci.org/lestard/FluxFX.svg?branch=master)](https://travis-ci.org/lestard/FluxFX)



### Flux architecture

The flux architecture is an alternative to Model-View-Controller build by Facebook for their JavaScript library [React](https://facebook.github.io/react/).



The key concept of flux is unidirectional data flow:



The application state is located in so called **Stores**.

**Views** are displaying the data of a the stores but they can't change the state pf the stores.

Instead the View has to publish **Actions**.

These actions are managed by a **Dispatcher** that dispatches *all* actions to *all* stores.

Each store can decide if it likes to handle an incoming action and can change it's internal state accordingly.

After a state change the store will emit a "change" event to the views so that the view can update itself.



### FluxFX



FluxFX follows this idea with some small exceptions to make it more suitable for the usage with JavaFX:



- Stores can "subscribe" to specific action types. Other actions aren't dispatched to the store.

- There is no explicit mechanism for "change events" from the Stores to trigger the re-rendering of views.

Instead it's recommended to use the Properties and unidirectional Data-Binding provided by JavaFX. Another great tool for this purpose are

the `EventStream`/`EventSource` classes from [ReactFX](https://github.com/TomasMikula/ReactFX).



Internally FluxFX uses the great library [ReactFX](https://github.com/TomasMikula/ReactFX) which is the only dependency.



To use FluxFX in your own project you can us the following config:



Gradle:



```groovy

dependencies {

    compile 'eu.lestard:fluxfx:0.1'

}

```



Maven:



```xml



    eu.lestard

    fluxfx

    0.1



```



Another example of the flux architecture with JavaFX (but without fluxfx) can be seen [here](https://github.com/lestard/juggr_model-view-star/tree/master/flux).



### Tutorial



In this short tutorial we are creating a simple notes app.



##### Create a basic Store



We start with the store class that will hold our notes data. In our case we will use a simple list of

strings:



```java

package notesapp;



import eu.lestard.fluxfx.Store;

import javafx.collections.FXCollections;

import javafx.collections.ObservableList;



public class NotesStore extends Store {



    private ObservableList notes = FXCollections.observableArrayList();



    public ObservableList getNotes() {

        return FXCollections.unmodifiableObservableList(notes);

    }

}

```



The store class extends from `eu.lestard.fluxfx.Store`.

Internally we use an observable array list.

But the public getter for the list returns an unmodifiable wrapper of our list.

This way we can be sure that the state can only be modified by the Store itself and not from

other classes.



##### Create a FXML file for the View (with [SceneBuilder](http://gluonhq.com/products/scene-builder/))



```xml



   

      

         

            

            

         

      

      

   

   

      

   



```

This FXML file produces this GUI:



![NotesApp](/examples/notesapp/notesapp.png)



Note that we have set the attribute `fx:controller` to `notesapp.NotesView`. We will create this class in the next step.



##### Create a View class



The view class acts as a connector between the Java logic and the FXML file.

We can inject references to the UI elements declared in the FXML file and fill them with data.



In the first step the view class looks like this:



```java

package notesapp;



import eu.lestard.fluxfx.View;

import javafx.fxml.FXML;

import javafx.scene.control.ListView;

import javafx.scene.control.TextField;



public class NotesView implements View {



    @FXML

    private ListView list;



    @FXML

    private TextField input;



    private NotesStore store = new NotesStore();



    public void initialize() {

        list.setItems(store.getNotes());

    }



    public void add() {

        // todo

    }

}

```



The intersting part is the `initialize` method. This method will be called automatically by JavaFX when the FXML file

is loaded. With the statement `list.setItems(store.getNotes());` the `ListView` will show the notes from the Store.

As the notes list is observable the ListView will update itself automatically when the state in the store is changed.



Another thing to notice is that we implement the `eu.lestard.fluxfx.View` interface. In the next steps we will see why.



##### Define an Action to add notes



With flux all changes to the applications state are triggered by *actions*.

In our case we like to add new notes so we create a class `AddNoteAction`.

An action implements the `eu.lestard.fluxfx.Action` interface:



```java

package notesapp;



import eu.lestard.fluxfx.Action;



public class AddNoteAction implements Action {



    private final String noteText;



    public AddNoteAction(String noteText) {

        this.noteText = noteText;

    }



    public String getNoteText() {

        return noteText;

    }

}

```



Actions can contain data but they should be immutable (i.e. data can't be changed after creation).



##### Trigger action in the View



We can now implement the `add` method in our view class.

When the user clicks the `add` button we will take the text from the input field and publish a new `AddNoteAction`.



```java

...

public class NotesView implements View {



    ...



    public void add() {

        publishAction(new AddNoteAction(input.getText()));

    }

}

```



The `View` interface has a method `publishAction` that we are using to bring our action into the system.



##### Process the action in the store



In our store we can subscribe to our action and perform the needed changes to the applications state.



```java

public class NotesStore extends Store {

    ...

    public NotesStore() {

        subscribe(AddNoteAction.class, new Consumer() {

            @Override

            public void accept(AddNoteAction addNoteAction) {

                final String noteText = addNoteAction.getNoteText();



                if(noteText != null && !noteText.trim().isEmpty()) {

                    notes.add(noteText);

                }

            }

        });

    }

    ...

}

```



In the constructor we use the `subscribe` method from the `Store` class.

The first param is the class type of the action we are interested in.

The second param is a `Consumer` function that is processing the incoming action.



With Java8 of cause we can use a **lambda** instead of the anonymous inner class for the consumer.

Even better is to create a method in the store and use a **method reference** in

the subscribe statement.

The method should be `private` or package scope (no access modifier) to prevent direct

invocation from outside of the store:



```java

public NotesStore() {

    subscribe(AddNoteAction.class, this::processAddNoteAction);

}



private void processAddNoteAction(AddNoteAction action) {

    final String noteText = action.getNoteText();



    if(noteText != null && !noteText.trim().isEmpty()) {

        notes.add(noteText);

    }

}

```



##### Create an application class and load the View



The last step is to create an application class with a `main` method and load the FXML file.

If your FXML file has the same name as the View class (except for the file ending of cause)

and is contained in the same package, you can use the `ViewLoader` class from FluxFX

to load it like this:



```java

package notesapp;



import eu.lestard.fluxfx.ViewLoader;

import javafx.application.Application;

import javafx.scene.Parent;

import javafx.scene.Scene;

import javafx.stage.Stage;



public class App extends Application {



    public static void main(String... args) {

        launch(args);

    }



    @Override

    public void start(Stage stage) throws Exception {

        final Parent root = ViewLoader.load(NotesView.class);



        stage.setScene(new Scene(root));

        stage.show();

    }

}

```



##### Testing



Testing code is crucial for real applications. With flux architecture

most logic is located in the store so let's write a unit test for our store.

If you are a fan of test-driven-design you could write the test even before implementing the store.



```java

import eu.lestard.fluxfx.Dispatcher;

import org.junit.Before;

import org.junit.Test;



import static org.assertj.core.api.Assertions.assertThat;



public class NotesStoreTest {



	private NotesStore store;



	@Before

	public void setup() {

		store = new NotesStore();

	}



	@Test

	public void testAddASingleNote() {



		// given

		assertThat(store.getNotes()).isEmpty();



		// when

		Dispatcher.getInstance().dispatch(new AddNoteAction("something"));



		// then

		assertThat(store.getNotes()).contains("something");

	}



	@Test

	public void testAddMultipleNotes() {



		// given

		assertThat(store.getNotes()).isEmpty();



		// when

		Dispatcher.getInstance().dispatch(new AddNoteAction("something"));

		Dispatcher.getInstance().dispatch(new AddNoteAction("second"));

		Dispatcher.getInstance().dispatch(new AddNoteAction("third"));



		// then

		assertThat(store.getNotes()).containsExactly("something", "second", "third");

	}



	@Test

	public void testAddEmptyNotes() {

		// given

		assertThat(store.getNotes()).isEmpty();



		// when

		Dispatcher.getInstance().dispatch(new AddNoteAction(""));

		// then

		assertThat(store.getNotes()).isEmpty();



		// when

		Dispatcher.getInstance().dispatch(new AddNoteAction(null));

		// then

		assertThat(store.getNotes()).isEmpty();



		// when

		Dispatcher.getInstance().dispatch(new AddNoteAction("    "));

		// then

		assertThat(store.getNotes()).isEmpty();

	}

}



```



In the example I'm using [JUnit](http://junit.org/junit4/) and [AssertJ](https://joel-costigliola.github.io/assertj/) for testing.

As there is no View available

in a Unit-Test we are directly using the `Dispatcher` to create new Actions.

The `publishAction` method that we have seen above in the View class is just a shortcut that delegates

the actions to the singleton Dispatcher in the same way.



If we had made our `processAddNoteAction` method in the store to be package scoped we could use it directly

in the test class and could skip the Dispatcher.

It's up to you which option you choose.



The complete code for this example can be seen in [the repository](/examples/notesapp).