Towards better serialization

[forax at univ-mlv.fr]

----- Mail original -----
> De: "Brian Goetz" <brian.goetz at oracle.com>
> À: "Remi Forax" <forax at univ-mlv.fr>
> Cc: "amber-spec-experts" <amber-spec-experts at openjdk.java.net>
> Envoyé: Mardi 11 Juin 2019 23:29:51
> Objet: Re: Towards better serialization

>> About the details,
>> - using factories, constructor and matchers: yes
>> - using annotations @Serializer/@Deserializer + version,
>>    this part is still too magic, no?, an annotation is not better than an empty
>>    interface, it's still not integrated with the language,
>>    @Serializer/@Deserializer should be keywords, and version can be a parameter,
>>    so you can disambiguate versions in code (framework may use annotation on top
>>    of that mechanism to provide a more declarative API).
> 
> While you know that I reject about 99% of the proposed uses of
> annotations as "that's not what annotations are for", this one really
> does fit the bill.  Because, what these annotations do is _capture
> design intent_ that these members are intended, by the author, to be
> usable by serialization frameworks for certain activities.  But it does
> not affect their accessibility, or semantics, or the generated
> bytecode.  The language has (almost) no interest in these annotations;
> they are a side-channel signal between a class and a serialization
> framework (and not just Java serialization) that these members are
> suitable and intended for a certain purpose.  (Yes, the compiler may
> wish to do additional type checking, like checking that the arguments
> lists for the serializer and deserializer are compatible, and issue
> diagnostics accordingly, but that's also within the rules for
> annotations, like @Override.)

The main difference between @Override, @FunctionalInterface and @Serializer/@Deserializer is that the formers are a form of documentation, the code still work if you remove them, it's not true with the two annotations you are proposing.

Those annotations add a new contract at the language level, so they should be keywords and not annotations.

Rémi