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Hi, using Eclipse 4.2.1 I observed the following: @Inject @Optional public void myMethod(@Named(IServiceConstants.ACTIVE_SELECTION)MyObject o) { } The method gets called at application startup. There is no MyObject instance loaded or displayed. As far as I unterstand the @Optional annotation at method level the method should not be called. The same code without the @Named annotation works as expected. Cheers Joachim
Hi, my problem is similar to the one of joachim: having a method annotated like this: @Inject public void setTodo(@Optional @Named(IServiceConstants.ACTIVE_SELECTION) MyObject o) { } it is called twice - i expected it is called only once through application startup. If the @Named is ommitted than it is called only once, but @Name should do only the "address stuff". Maybe my test or opion is wrong? Thanks Sven
@Paul, maybe some hints for potential contributors where to look would be helpful?
First check, is it just active selection, or does it happen with any @Named constant? PW
Created attachment 227293 [details] snippet from a view to test @Optional's startup behaviour
(In reply to comment #3) > First check, is it just active selection, or does it happen with any @Named > constant? Well, I tried ACTIVE_SELECTION, ACTIVE_PART and ACTIVE_SHELL and they all are passed as null with @PostContextCreate. The ACTIVE_PART is being passed 3 times as null before being an object reference: F expecting the active shell Shell {} G expecting the active part null unexpected E inject optional method selection null G expecting the active part null F expecting the active shell Shell {} G expecting the active part null F expecting the active shell Shell {} G expecting the active part org... F expecting the active shell Shell {} G expecting the active part org... F expecting the active shell Shell {} (see code attachement above)
@Optional on a method means: if the key cannot be resolved, the injection should be skipped rather than raise an InjectionException. null is an acceptable value to be set in the context, and it is different from a key being removed from the context. i.e., context.set(SOMEKEY, null); means anybody listening for SOMEKEY will be injected with null. If you look through the code, there are a number of places where the ACTIVE_SELECTION is explicitly set to null, such as when there is no active part and hence no active selection. If you weren't injected with null, you'd have no way to know that the active selection changed to nothing. null is the equivalent of an empty IStructuredSelection in the 3.x selection model.
(In reply to Brian de Alwis from comment #6) > @Optional on a method means: if the key cannot be resolved, the injection > should be skipped rather than raise an InjectionException. > > null is an acceptable value to be set in the context, and it is different > from a key being removed from the context. i.e., > > context.set(SOMEKEY, null); > > means anybody listening for SOMEKEY will be injected with null. Maybe we should add this to the Javadoc of @Optional? Opened Bug 468291 for this.
