Portable retrieval of resource bundles across module path and class path

[Mandy Chung]

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