code: private String encodeBatch (Batch<String> batch) throws IOException {
      // Convert original json object to a new json object with format {"Body": "originalJson"}
      // Add new json object to an array and send the whole array to eventhub using REST api
      // Refer to https://docs.microsoft.com/en-us/rest/api/eventhub/send-batch-events
      List<String> records = batch.getRecords();
      ArrayList<EventhubRequest> arrayList = new ArrayList<>();
  
  
      for (String record: records) {
        arrayList.add(new EventhubRequest(record));
      }
      return mapper.writeValueAsString (arrayList);
    }
docs: Each record of batch is wrapped by a 'Body' json object
  put this new object into an array, encode the whole array