Web Transactions

If your host needs to perform web requests (e.g. GET, PUT, POST, or DELETE) with a 3rd party API or cloud service, the Notecard can facilitate these requests with the web.get, web.put, web.post, and web.delete APIs.

Consult the web Requests API reference for more extensive information on using the web.* APIs.

Requirements for Using Web Transactions

Use of these requests in the Notecard API requires the following:

1) The Notecard must be in continuous mode and connected to Notehub.

For example:

{
  "req": "hub.set",
  "product": "com.your-company.your-name:your_product",
  "mode": "continuous"
}

J *req = NoteNewRequest("hub.set");
JAddStringToObject(req, "product", "com.your-company.your-name:your_product");
JAddStringToObject(req, "mode", "continuous");

NoteRequest(req);

req = {"req": "hub.set"}
req["product"] = "com.your-company.your-name:your_product"
req["mode"] = "continuous"

card.Transaction(req)

If any of the web.* requests are issued to a Notecard not in continuous mode or not connected, an error will be returned:

{ "err": "web operations require being online (hub.set)" }

2) The endpoint to the 3rd party API or cloud service must be configured as a proxy Route in Notehub as a "Proxy for Device Web Requests" type.

This allows the host to avoid hardcoded URLs, keys, and certificates, while relying on Notehub secure authentication mechanisms for performing requests.

Once the device is in continuous mode and the proxy Route is created, use web.get, web.put, web.post, or web.delete in accordance with the requirements of the final endpoint.

For example, the Route shown above creates a proxy to a GET request to the weather endpoint of the OpenWeatherMap API. The route argument corresponds to the Route Alias specified when the proxy Route is created.

Note that you may optionally enable caching so that web.get requests return cached results to reduce latency and provide you with more control over Consumption Credit usage (i.e. cached responses do not cost CCs). When handling a web.get request with caching enabled, Notehub honors the Cache-Control response header as per RFC7234 with a minimum cache TTL of 5 minutes.

{
  "req": "web.get",
  "route": "weatherInfo"
}

J *req = NoteNewRequest("web.get");
JAddStringToObject(req, "route", "weatherInfo");

NoteRequest(req);

req = {"req": "web.get"}
req["route"] = "weatherInfo"

rsp = card.Transaction(req)

For all web requests, the Notecard returns the HTTP Status Code in the result field. If the response also contains a body, that body is provided in the body field.

warning

The Notecard can only accept valid JSON in response to a GET, POST, or PUT request unless you override the default content argument of application/json with the appropriate MIME type.

{
 "result": 200,
 "body": {
  "base": "stations",
  "clouds": {
   "all": 75
  },
  "coord": {
   "lat": 42.5776,
   "lon": -70.87134
  },
  "name": "Beverly",
  "weather": [
   {
    "description": "broken clouds",
    "icon": "04d",
    "id": 803,
    "main": "Clouds"
   }
  ],
  "wind": {
   "deg": 240,
   "speed": 5.1
  }
 }
}

note

Data returned by a proxy Route is delivered to the Notecard unmodified. To preserve power and data, make sure the APIs you're working with return only the data needed by your host, if possible.

For web.put and web.post requests, a JSON body OR base64-encoded payload can be provided using the body or payload arguments. Unlike the note.add API, you cannot use both at the same time in a single web transaction.

{
  "req": "web.post",
  "route": "SensorService",
  "name": "/addReading",
  "body": { "temp": 72.32, "humidity": 32.2 }
}

J *req = NoteNewRequest("web.post");
JAddStringToObject(req, "route", "SensorService");
JAddStringToObject(req, "name", "/addReading");

J *body = JCreateObject();
JAddNumberToObject(body, "temp", 72.32);
JAddNumberToObject(body, "humidity", 32.2);
JAddItemToObject(req, "body", body);

NoteRequest(req);

req = {"req": "web.post"}
req["route"] = "SensorService"
req["name"] = "/addReading"
req["body"] = {"temp":72.32, "humidity":32.2}

rsp = card.Transaction(req)

After performing a web request, don't forget to set your Notecard back into a non-continuous mode, if needed, using hub.set.

Sending Large Payloads to Notehub

Consult our guide on Sending and Receiving Large Binary Objects if your application needs to send large binary payloads to Notehub.