How to set the channel variable in ASTERISK ARI

Initiating the call using the code

 Map<String,String> channelVar = new HashMap<>();
        channelVar.put("UID",callRequest.getUid());
        channelVar.put("asterisk_context",outContext);
        channelVar.put("sipGateway", suffix);
        channelVar.put("outCallerId",outCallerId);
        channelVar.put("timeout",timeout);
        channelVar.put("TO",callRequest.getExtraParams().get("TO"));
  
 Channel channel = ARIApp.ari.channels().originate("PJSIP/8224XXXXX")
                    .setApp(ARIApp.APP_NAME)
                    .setAppArgs(callRequest.getUid())
                    .setCallerId(outCallerId)
                    .setVariables(channelVar)
                    .setTimeout(Integer.parseInt(timeout))
                    .setChannelId(channelId)
                    .execute();

Once I get the call and answered the same I am getting stasis start event in application there i am checking these channel variable but i am getting null only.

String uid = ARIApp.ari.channels().getChannelVar(channelId,"UID").execute().getValue();

I tried setting after call initiate also but that is also not working