Eclipse-RCP: Getting Resourcebundles using custom ResourceBundle.Control

Question

We load our translations from our database. To retrieve the bundles we have a custom java.util.ResourceBundle.Control.

To translate our e4 RCP application, I already created a TranslationService, which I add to the root context using an addon. That was no problem (only that I had to copy 95% of BundleTranslationProvider because I did not see any other way).

Now I want to use the new Message Extension (coming with Eclipse Luna) to translate the rest. As far as I can see from the sources of the default MessageFactoryServiceImpl, there does not seem to be an easy way to inject my ResourceBundle.Control there either.

In the linked blog series, the use case of getting the resource bundles from a database is described, but solved by using class based resource bundles. This is no option, because I can't implement a class for every resource bundle and every locale. The reason for loading the resource bundles from the database is to be able to deploy translations into new languages without redeploying the application.

Is the only way to achive this by creating my own IMessageFactoryService by copying 99% of the default MessageFactoryServiceImpl, just to pass our Control into the calls to ResourceBundleHelper?

Answer 1

After some investigation on this, I found a way that you are able to support your use case without modifying or copying code a lot.

You need to exchange the BundleLocalization to load the ResourceBundle your way. In your case by using your custom ResourceBundle.Control. By doing this you override that the platform is looking for the ResourceBundle specified by the MANIFEST.

At the moment you will also have to implement a custom TranslationService that uses your BundleLocalization. The existing BundleTranslationProvider does not take the BundleLocalization out of the context. And you will need to copy a lot of code there, because getBundle() is private. I will discuss possible modifications with the developers.

You can find an example here: https://github.com/fipro78/e4classbasedtranslation

Hope that helps you to solve your specific requirement.

Answer 2

AFAIK ResourceBundle.Control is used to load ResourceBundles. In the new Message Extension we use a custom ResourceBundle.Control to enable the loading of ResourceBundles in the OSGi context, and it is configurable via annotations.

AFAICS exchanging the ResourceBundle.Control will break any other use case supported by the new Message Extension.

The question is, why do you use a custom ResourceBundle.Control instead of creating a class based ResourceBundle? I haven't tried it yet, but maybe it is possible to create only the base ResourceBundle (without Locale information) and determine the Locale in another way than using getLocale().

But without knowing what you are doing in your custom ResourceBundle.Control, I don't know what to answer and what to suggest. Of course we could open the API for that, but as I said before, then every other plugin that makes use of the default implementation will fail.

Maybe you can give some hints on what you are doing exactly and I can show you a way to achieve your goal in another way.