Re: [Communicator-user] Java bindings

[<woh...@mi...>]

Sam's explanation looks correct to me. In particular, the signature info is really only used for validation purposes (an optional step).

- Steve

"Samuel L. Bayer" wrote:

>    We found that writing a Java based server is somewhat different to doing it
>    using C. Especially, we are concerned of the signature definition routines,
>    initSignatures, SigEntry, Signature and addSignature.  As I have understood
>    it, one has to define the exact nature of input and output frames for each
>    dispatch function of the server. However in our case we have two problems
>    regarding this,
>
> Narada -
>
> This is a good question, and I apologize that the docs are
> unclear. The examples in contrib/MITRE/examples/double certainly show
> a complete specification of the signature. However, there are a number
> of ways of defining the signature. I'm far from an expert on Java;
> Steve Wohlever covers that area for us. Normally, I'd let him reply,
> but he may be out for a few days for our Thanksgiving break. So let me
> give this a shot.
>
> You only need to use the signature stuff if you want to specify a
> signature, as shown in the code from
> contrib/MITRE/examples/double/java/Multiply.java:
>
>     private void initSignatures() {
>         SigEntry[] foo = {new SigEntry(":int",GalaxyObject.GAL_INT, Signature.GAL_KEY_ALWAYS)};
>         addSignature(new Signature("multiply", foo , Signature.GAL_OTHER_KEYS_NEVER, foo, Signature.GAL_OTHER_KEYS_NEVER, Signature.GAL_REPLY_PROVIDED));
>     }
>
> The signatures are used only informationally, for validation
> purposes. They're sent to the Hub when the server and Hub connect, but
> the only effect they currently have is validation. So to answer one of
> your questions, no, initSignatures() isn't necessary. As you're
> probably aware, the Java bindings map message names to methods named
> "serverOp<capitalized_message_name>", no matter whether a signature is
> declared or not. See contrib/MITRE/examples/audio/java for cases where
> no signatures are registered.
>
> If you want to use signatures, you can use the constants
> Signature.GAL_KEY_SOMETIMES and Signature.GAL_OTHER_KEYS_MAYBE in
> the appropriate places to indicate, respectively, that a key is
> possible but not required and that other keys are permitted.
>
> I'll admit that this mechanism wasn't designed for the case you
> describe, where you're treating a dispatch function as polymorphic,
> essentially. So this mechanism doesn't admit alternative signatures,
> for instance. However, the mechanism itself is currently fairly
> non-central to the infrastructure, so this particular defect doesn't
> concern me much.
>
> If any of this is wrong, I'm sure Steve will chime in, perhaps after
> he comes back from vacation.
>
> Cheers,
> Sam