[FIXED] cannot inject a dependency in a javafx project

Issue

I am trying to do dependency injection in a javaFX project.

I have a

@Singleton
public class WidgetFactory implements IWidgetFactory

My public class ZentaEditorModule extends MvcFxModule contains

  @Override
  protected void configure() {
    super.configure();
    //some other code
    System.out.println("binding WidgetFactory");
    bind(IWidgetFactory.class).to(WidgetFactory.class);
  }

In my public class ZentaApplication extends Application I have this, running in application initialization:

final Injector injector = Guice.createInjector(module);
System.out.printf(
    "widgetFactory=%s\n", injector.getInstance(IWidgetFactory.class)
);
domainHandler = new DomainHandler(injector, editorModel);

And the DomainHandler starts like this:

public class DomainHandler {

  @Inject
  private IWidgetFactory widgetFactory;
  @Inject
  private Injector injector;

  public DomainHandler(
      final Injector injector, final EditorModelItem editorModelItem
  ) {
    System.out.printf(
        "injector in domainHandler=%s\n",
        injector
    );
    System.out.printf(
        "injector2 in domainHandler=%s\n",
        getInjector(null)
    );
    System.out.printf(
        "widgetFactory in domainHandler=%s\n",
        widgetFactory
    );
    System.out.printf(
        "injector parameter=%s\n",
        this.injector
    );
 }
  @Inject
  public Injector getInjector(final Injector injector) {
    return injector;
  }
}

And I got this:

binding WidgetFactory
widgetFactory=org.rulez.demokracia.zenta3.editor.widgets.WidgetFactory@39957a81
injector in domainHandler=Injector[bindings=[ProviderInstanceBinding[key=Key[type=com.google.inject.Injector...
injector2 in domainHandler=null
widgetFactory in domainHandler=null
injector parameter=null
DomainHandler constructor

The injector output actually contain this:

LinkedKeyBinding[key=Key[type=org.rulez.demokracia.zenta3.editor.widgets.IWidgetFactory,
 annotation=[none]],
 source=org.rulez.demokracia.zenta3.editor.ZentaEditorModule.configure(ZentaEditorModule.java:152),
 scope=Scopes.NO_SCOPE,
 target=Key[type=org.rulez.demokracia.zenta3.editor.widgets.WidgetFactory,
 annotation=[none]]],

From that it seems that nothing get injected into my DomainManager instance, at none of the @Inject annotations. Interestingly there are other classes in the code which also have the injector injected, and those are working. So I guess I do something wrong at the initialization. But what?

Solution

Youre not creating your domainhandler through guice and therefore the @inject annotations do nothing. If you want to create this object both ways just use constructor injection and remove the @inject from your fields.

@inject
public DomainHandler(Injector injector, WidgetFactory widgetFactory) {
    this.injector = injector;
    this.widgetFactory = widgetFactory 
} 

This way passing them in manually or using getInstance will do the same thing.

@inject on getters doesn't make sense, it can be used on getters but even in the docs is says not normally, and your passing it a null when you print it from your constructor.

Answered By - kendavidson