how to inject a list?

[magick93]

Hi all

We have a page, that calls a service - and this service returns a list<Indicator>.

Then, we have several client Composite components that dependant on this List<Indicator> result.

These components are instantiated at different times.

My thinking was that, perhaps we can @Inject the List<Indicator>, however this does not work.

I also tried using an Event<Indicator> with an Observer, however, I assume, due to the event firing before the components had been instantiated,this did not work.

Currently, we have a tightly coupled dependancy on the List<Indicator> being passed on the page that the components are used.

I'm hoping we can inject this in some way.

What / how do you advise we achieve this?

[edewit]

Hi Anton,

Do you mean how to use them in errai-ui? If so you can use an ListWidget or create an Provider to inject the list

Cheers,

     Erik Jan

[magick93]

Hi Erik

The data in the List<Indicator> is used in the UI, however, the data in the list is displayed differently in different components.

I am already using the ListWidget now to display the items on the page.

However, there are other components that need this data.

For example, we have a component that shows in a modal window, and uses data from the List<Indicator>. We either have to explicity pass this list from the page to the component, or again call the service.

So, I am looking for a way to:

Call the service once, and retrive the List<Indicator>

And have this value available for client components without being tightly coupled.

[jfuerth]

Have you tried an application-scoped producer? Maybe something like this:

@ApplicationScoped
public class IndicatorBeanProvider {

  @Produces
  private List<Indicator> indicatorList;


  @AfterInitialization
  private void fetchIndicatorList() {
    indicatorService.call(...callbacks...).getIndicators();
  }
}

and in the callback from the RPC, assign the response value to indicatorList. Then wherever you @Inject List<Indicator>, the CDI context should inject the same list that the producer field references.

I think this should work for your use case. It would not work if you required a different list of indicators to be injected at different injection points, although you could possibly use CDI qualifiers to solve that problem.

-Jonathan

[magick93]

Thank you Jonathan!

That tip signifcantly cleaned up our code!