AVRO-4147: Mention ServiceLoader in SchemaFormatter javadoc

[opwvhk]

What is the purpose of the change

Implement AVRO-4147 by updating the javadoc for the SchemaFormatter interface

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[nandorKollar]

LGTM, though it appears to me, that SchemaFormatterFactory is located via ServiceLoader, not the SchemaFormatter implementations. Nevertheless, eventually the factory is used to create the formatters, so it might worths mentioning service loading here too.

[opwvhk]

Thank you @nandorKollar !
Your comment is entirely correct, and the javadoc for SchemaFormatterFactory already mentions it. The reason for this comment however, is because I encountered a class loading issue when trying to use the SchemaFormatter in a non-standard environment (an IDE plugin).

The reason it didn't work, is because the class needed to be loaded using the context ClassLoader: neither my plugin nor Avro were available at application start, so the application ClassLoader could not find it.

I'm not certain though, whether I should mention that explicitly or if a reference to the ServiceLoader is sufficient.

[nandorKollar]

Thank you @nandorKollar ! Your comment is entirely correct, and the javadoc for SchemaFormatterFactory already mentions it. The reason for this comment however, is because I encountered a class loading issue when trying to use the SchemaFormatter in a non-standard environment (an IDE plugin).

The reason it didn't work, is because the class needed to be loaded using the context ClassLoader: neither my plugin nor Avro were available at application start, so the application ClassLoader could not find it.

I'm not certain though, whether I should mention that explicitly or if a reference to the ServiceLoader is sufficient.

I think it makes sense briefly highlighting this scenario, that could clarify why ServiceLoader is mentioned here too.

[nandorKollar]

@opwvhk one more thing: I think you should run mvn spotless:apply to fix style violations.

[opwvhk]

🤦 spotless...