Portable retrieval of resource bundles across module path and class path

[Gunnar Morling]

Hi all,

I've written a quick blog post about my experiences with
ResourceBundleProvider et al.:


https://www.morling.dev/blog/resource-bundle-lookups-in-modular-java-applications/

 The scenario I'm describing is that of a "well-structured monolith", with
each module contributing its own resource bundle(s). It took a while to set
things up in a way working with Java 9+ (with module and with classpath)
and Java 8, but I've found my ways in the end.

Thanks again for all the feedback and input you provided!

Best,

--Gunnar



Am Fr., 23. Juli 2021 um 21:14 Uhr schrieb Mandy Chung <
mandy.chung at oracle.com>:

>
>
> On 7/23/21 4:17 AM, Gunnar Morling wrote:
>
> Thanks a lot for your replies, Mandy and Alan!
>
> > I assume the class path is running on JDK <= 8, right?  Otherwise
>
> Is there something missing after "Otherwise"?
>
>
> It was a typo (I should have taken it out).
>
> In fact, I'm looking for a way to run this
>
> - Java 1.8 on classpath
> - Java 9+ on classpath
> - Java 9+ on module path
>
> As I've learned by now, ResourceBundleControlProvider implementations on
> Java 1.8 will only be loaded via the extension mechanism, which often is
> impractical to use. So it seems I'll need to amend my solution described
> above to pass in the custom Control explicitly to
> ResourceBundle.getBundle(). I could use the ResourceBundleControlProvider
> in a MR JAR, but there seems not much of an advantage to doing that.
>
> > For the migration scenario where the resources are in .properties format
> then the simplest may be to just deploy the JAR files on the module path
> where they will be treated as automatic modules.
>
>
> Right, this is indeed the simplest approach if the JAR file contain
> resource bundles in .properties format and no .class files in that
> package.  i.e. you can keep the resource bundles in `dev/morling/greeter`
> and deploy them as automatic modules.
>
>
> In the scenario I have in mind (for educational purposes mainly) the JAR
> files contain the properties file as well code and should be usable as
> "proper" (i.e. non-automatic) modules as well as on the classpath.
>
>
> It's common to have the resources packaged in separate JARs from the code
> and also an application includes all resources.   This educational purpose
> demo shows an advanced feature.
>
>
> > There are no split package issues unless the resources have been
> compiled as .class files.
>
> That's very interesting, it's not what I observe. Having the *.properties
> in one and the same package in multiple modules triggers an error upon
> start-up:
>
>     java.lang.LayerInstantiationException: Package dev.morling.greeter.fr
> <https://urldefense.com/v3/__http://dev.morling.greeter.fr__;!!ACWV5N9M2RV99hQ!fILkGEkNjEpD7sQnRSKHS3M4qZY3lXvfXij2Q4XgaGa9P1mVdmrAFrdcvVKsPREq3A$>
> in both module dev.morling.greeter.german and module
> dev.morling.greeter.french
>
>
> this looks a little suspicious.   GreetingMessages_de.properties should be
> expected in dev.morling.greeter.
>
> Mandy
>