terça-feira, 10 de outubro de 2017

Using CDI 2.0 in a JavaFX application

With the CDI 2.0 release we have a container that can be used in Java SE applications! Previously if you wanted to make use of CDI 1.x in a Java SE application you had to use Weld classes, see FXML & JavaFX—Fueled by CDI & JBoss Weld post.

Adam Bien introduced the SE container in a video, see:

Of course I had to try it with JavaFX so I can use CDI in some personal applications!

Create the Container in a JavaFX Application

By JavaFX application I mean the class that extends javafx.application.Application, which is the entry point for JavaFX apps and where the main stage can be used. To use CDI we should create the SeContainer and make sure that it create all classes managed by CDI. This should be done in the entry point Application class so we manage all the classes created from there.

Once you started the container you have different ways to send the initial stage to the actual Application class, for example, you can have users to implement an interface and then use the CDI container to select a bean that implements the interface, for example:

There's a more elegant way which is by using CDI Observer API. In this case we may create an annotation that will be the qualifier for the event javafx.stage.Stage. CDI will wisely know all classes that observes that event and will select the user classes when we fire it by sending the primary stage. This is similar to what was done in FXML & JavaFX—Fueled by CDI & JBoss Weld post:

Whatever approach you chose, just make sure to not shutdown the container or it may bring inconsistencies (actually I think it will work in most of the cases, but I decided to not shutdown it).

Ok, now you can use CDI in your application! Go ahead and inject stuff in your class. Unless of course if you are using FXML and in this case FXML will create the controllers for you using reflection, and CDI won't work there, unless we use CDI itself to produce a FXMLLoader instance and in this case we can set a callback to create the bean using CDI, so all the injected fields won't be null. The code was taken from  FXML & JavaFX—Fueled by CDI & JBoss Weld post because it didn't have change at all, we are just using Java 8 delicious lambdas,  see:

Finally you can create your own app, but never call FXMLLoader static methods when using CDI, instead, use the injected one:

Remember that you are also able to inject stuff in your controller. In my case I injected a classic Greeter to the controller:

Also, since this a CDI application we should not forget about the empty beans.xml file. This is the structure of the project I used in my tests:

This is the final result with the fact that now the message is coming from a CDI Bean:

The full project can be found in my github.

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