CODEWITHSUNDEEP
azure-functionsazure-iot-hubazure-eventhub
jabrena
jabrena

Reputation: 1345

How to deserialize an Event from IoT hub which it was passed to an Event-hub?

I am processing a message from an EventHub connected with an IoT Hub. I will try to explain the whole process.

Using a terminal, I send the following command to an IoT hub component deployed on Azure:

  curl --request POST \
    --url "https://${IOT_HUB}.azure-devices.net/devices/${DEVICE}/messages/events?api-version=2018-06-30" \
    --header "Accept: application/json" \
    --header "Authorization: ${SAS_TOKEN}" \
    --data "{ \"field1\" : \"12345\", \"field2\" : \"abcde\" }" \
    --verbose

When the Azure function receive the event (curl -> IoT hub -> Event-hub <- Azure Function) and print the content:

    @FunctionName("processSensorData")
    public void processSensorData(
            @EventHubTrigger(
                    name = "demo",
                    eventHubName = "", // blank because the value is included in the connection string
                    cardinality = Cardinality.ONE,
                    connection = "EventHubConnectionString")
                    String item,
            final ExecutionContext context) {

        context.getLogger().info("Event hub message received: " + item.toString());

I receive the following message in the console:

    [
    {
       "id":"xxx",
       "topic":"/SUBSCRIPTIONS/xxx/RESOURCEGROUPS/xxxPROVIDERS/MICROSOFT.DEVICES/IOTHUBS/Txxxx",
       "subject":"devices/xxx",

   "eventType":"Microsoft.Devices.DeviceTelemetry",
   "eventTime":"2020-04-13T15:02:15.253Z",
   "data":{
      "properties":{

      },
      "systemProperties":{
         "iothub-content-type":"application/x-www-form-urlencoded",
         "iothub-content-encoding":"",
         "iothub-connection-device-id":"xxx",
         "iothub-connection-auth-method":"{\"scope\":\"device\",\"type\":\"sas\",\"issuer\":\"iothub\",\"acceptingIpFilterRule\":null}",
         "iothub-connection-auth-generation-id":"xxx",
         "iothub-enqueuedtime":"2020-04-13T15:02:15.253Z",
         "iothub-message-source":"Telemetry"
      },
      "body":"yyy"
   },
   "dataVersion":"",
   "metadataVersion":"1"
}]

but the body appear to be encrypted.

How to decode the body to return the original request?

"{ \"field1\" : \"12345\", \"field2\" : \"abcde\" }"

Many thanks in advance

Juan Antonio

Upvotes: 0

Views: 798

Answers (2)

Roman Kiss
Roman Kiss

Reputation: 8235

You should setup the system message properties such as the contentType to application/json and contentEncoding to UTF-8 in your POST request.

Upvotes: 1

Serkant Karaca
Serkant Karaca

Reputation: 2034

Body is base64 URL encoded. You should decode it in your code and then parse the JSON object out. Try this code for decoding:

  var base64EncodedBytes = System.Convert.FromBase64String(base64EncodedData);
  var jsonStr = System.Text.Encoding.UTF8.GetString(base64EncodedBytes);

Upvotes: 0

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