Problem: JNI binding generator can't handle function pointers as method parameters

[bluca]

https://github.com/zeromq/zproject/blob/master/zproject_java_lib.gsl#L156

        if resolve_container (argument) = 1
            my.method.okay = 0
            #echo "Skipping $(class.name).$(my.method.name) - can't deal with argument type $(argument.type)"

So the class is skipped given the constructor can't be generated.

This is a problem in CZMQ since it means that zactor bindings can't be generated. We'd need some help here from JNI experts! How can we fix this?

zeromq/czmq#1443

[jimrthy]

It looks to me as though this is also a problem with ZLoop.

[jimrthy]

I'm not an expert in any of the tech involved here.

I think one valid approach would be:

• the caller needs to supply an instance that fulfills some sort of ICallback interface (much like you hand anonymous event handler instances to Swing)
• we set up a C-level callback wrapper to hand to the 0mq API
• that callback's "args" parameter is a struct that contains
  • JNI environment pointer
  • method ID
  • "real" arguments
• that callback wrapper function does the "real" callback

I took a first pass at this approach (and started pointing out the places that look obviously broken) here:
jimrthy#1

I probably won't get another chance to look at this until next weekend, at the earliest.

Maybe someone who's more familiar with GSL can help push it further along?

[sappo]

Thanks for investigating I'll give it at try next week

[jimrthy]

Thank you!

[sappo]

@jimrthy I havn't forgotten this issue but I'm a bit short on time for time being.

[jimrthy]

I haven't forgotten either. Just also distracted by other things.

[diorcety]

Could you take a look on https://github.com/diorcety/zproject/tree/x_java2 ?

[diorcety]

python use ffi in order to handle the callbacks. I used jffi which is an Java implementation which allow to use java callback quickly. This is almost the same thing that python stuff

[sappo]

Neat, I'll have a look at it later, thanks Am 12.02.2018 3:55 nachm. schrieb "Diorcet Yann" <notifications@github.com>:

…

python use ffi in order to handle the callbacks. I used jffi which is an Java implementation which allow to use java callback quickly. This is almost the same thing that python stuff — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#776 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAeGuiJ5IfS-49StUlazgLunPsbrx5Xbks5tUFDlgaJpZM4LY7dS> .

[hgourvest]

I managed to write a pure java class for zactor, and doing this I also discovered zsys::create_pipe was not working for the same reason, it pass a pointer to a handle.

[stephan57160]

Found this link, but unable to see if really useful or not:
https://stackoverflow.com/questions/819536/how-to-call-java-functions-from-c

(my 2 cents).