Invoking other parts of the Cumulocity IoT REST API
The Cumulocity IoT REST API covers some extra functionality which is not covered with the individual event types. To invoke any other part of the REST API, a generic request/response API is provided which you can use to invoke any part of the Cumulocity IoT API.
To create the GenericRequest, always use new GenericRequest and then individually set whichever fields are needed by name. You must always set the reqId (which is used to tie requests and responses together) to a unique identifier generated by the com.apama.cumulocity.Util.generateReqId() action. You will also need to set the HTTP method (also known as the verb) and path. For some APIs, you will also need the queryParams (which populates the query string), body (typically a sequence or dictionary that will be converted to JSON by the plug-in) and/or additional HTTP headers. The GenericRequest event should be sent to the channel specified by the GenericRequest.SEND_CHANNEL constant.
To receive responses, you must subscribe to the channel given in the GenericResponse.SUBSCRIBE_CHANNEL constant. The response events will contain the reqId identifier specified in the request, as well as a body in a dictionary<any,any> where the AnyExtractor can be used to extract the expected content. This dictionary contains a structure which is equivalent to the JSON payload returned by Cumulocity IoT. For the cases where no body is expected in the response (for example, for a DELETE request), only a GenericResponseComplete event will be received for the request identifier.
When using an API which returns a collection, the results are automatically split into multiple GenericResponse events, followed by a GenericResponseComplete, all with the reqId identifier provided in the request.
Here is a simple example of using the API:
GenericRequest request := new GenericRequest;
request.reqId := com.apama.cumulocity.Util.generateReqId();
request.method := "GET";
request.isPaging := true;
request.path := "/measurement/measurements";
monitor.subscribe(GenericResponse.SUBSCRIBE_CHANNEL);
on all GenericResponse(reqId=request.reqId) as response
and not GenericResponseComplete(reqId=request.reqId)
{
AnyExtractor dict := AnyExtractor(response.getBody());
AnyExtractor source := AnyExtractor(dict.getDictionary("source"));
try{
AnyExtractor speed :=
AnyExtractor(dict.getDictionary("c8y_SpeedMeasurement")["speed"]);
log "Found measurement of type: c8y_SpeedMeasurement with id : " +
dict.getString("id") + " and source id :" + source.getString("id") +
" and speed "+speed.getFloat("value").toString()+
" "+speed.getString("unit")
at INFO;
}
catch(Exception e){
log "Failed to parse unexpected measurement : " +
dict.toString() at WARN;
}
}
on GenericResponseComplete(reqId=request.reqId)
{
monitor.unsubscribe(GenericResponse.SUBSCRIBE_CHANNEL);
}
send request to GenericRequest.SEND_CHANNEL;