@adora-tech asked the question in the Welcome thread #167

Hello all,

I am new to java programming and I hope to have an understanding from the maintainers.

I need to write an application in which I have to implement a state machine.
In a certain state I need to treat for example an event of type 'ChannelHangupRequest' with a certain id, only once, and then I need to close/remove the listening of that type of event.
Further in a new state it is possible to listen again to an event of the same type (ex. 'ChannelHangupRequest') and so on.
I need this because a sequence of events of the same type is received "by construction" on the websocket and this can lead to unwanted behaviors in the application.

On the Asterisk site there are examples written in python and javascript "Introduction to ARI and Media Manipulation / ARI and Media: Part 1 - Recording" which produces the behavior described above.

https://wiki.asterisk.org/wiki/display/AST/ARI+and+Media%3A+Part+1+-+Recording

In the examples (see at the end of the post), they subscribe to a 'ChannelHangupRequest' or 'ChannelDtmfReceived' event, as follows:

python

self.hangup_event = self.call.channel.on_event ('ChannelHangupRequest', self.on_hangup)
self.dtmf_event = self.call.channel.on_event ('ChannelDtmfReceived', self.on_dtmf)

javascript

call.channel.on ("ChannelHangupRequest", on_hangup);
call.channel.on ("ChannelDtmfReceived", on_dtmf);

and then somewhere in the code unsubscribe from events 'ChannelHangupRequest' or 'ChannelDtmfReceived', as follows:

python

self.hangup_event.close ()
self.dtmf_event.close ()

javascript:

call.channel.removeListener ('ChannelHangupRequest', on_hangup);
call.channel.removeListener ('ChannelDtmfReceived', on_dtmf);

In the examples on github/ari4java I could not find or understand how to unsubscribe(cleanup in the examples) from a particular event/events.
The question is, what is the correct approach in java and ari4java library, to get the behavior presented in the examples on the Asterisk site?

For maintainers, it would be very useful if the examples on the Asterisk site in python and javascript, can be replicated in as much detail as possible, using java and ari4java:

https://github.com/asterisk/ari-examples
https://wiki.asterisk.org/wiki/display/AST/ARI+and+Media%3A+Part+1+-+Recording
https://wiki.asterisk.org/wiki/display/AST/ARI+and+Media%3A+Part+2+-+Playbacks

I really appreciate your work.
Thank you!