I came across a recent blog entry about using ServiceLoader in a modular
environment:
https://blog.frankel.ch/migrating-serviceloader-java-9-module-system/
Unfortunately, it is completely wrong in its advice on "Migrating to the
Java Platform Module System". I have seen the same bad advice on
StackOverflow, so let me correct it here, as simply as possible:
1. The module containing the implementation SHOULD NOT export the
implementation package.
2. The module containing the client MUST say that it uses the service
interface.
See the "Deploying service providers as modules" section of
https://docs.oracle.com/en/java/javase/13/docs/api/java.base/java/util/ServiceLoader.html
The whole point of integrating ServiceLoader with the module system was
get the configuration documented explicitly, via `uses` and `provides`
clauses. Benefits: the implementation is strongly encapsulated (no
`exports`), and the client's service lookup is speedy because its
dependency (`uses`) was found cheaply during startup. Eventually, as the
blog rightly says, "only the configuration changes: the Service Loader
code itself in the client doesn’t change."
Alex
