Chapter 9. Creating ReST Interface

18.01.2022 — HaeramKim, BuildYourOwnIoTPlatform — 1 min read

NOTE: this notes are from “Build Your Own IoT Platform” by Anand Tamboli. And I can’t speak english very well, so some sentences or word might be inappropriate and might have some misunderstandings.

Make “ReST/GET Records Based on Condition” Funtionality

It’s simple; Fetch some records by topic-like, payload-like, count.
HTTP in node: Set method as GET and URL as /records/topic-like/:topic/payload-like/:payload/last/:count.
function node:

1// Create query
2
3// if no authentication filter defined or available
4// set the default value as 1
5if(!msg.req.authFilter)
6    msg.req.authFilter = 1;
7
8// wildcard used for API query is * and this needs to be converted into SQL wildcard character %
9msg.topic = "SELECT id,topic,payload,timestamp" +
10            " FROM thingsData WHERE" +
11            " topic LIKE '" + msg.req.params.topic.
12            replace(/\*/g, "%") + "'" +
13            " AND" +
14            " payload LIKE '" + msg.req.params.payload.
15            replace(/\*/g, "%") + "'" +
16            " AND deleted=0" +
17            " AND (" + msg.req.authFilter + ")" +
18            " ORDER BY ID DESC" +
19            " LIMIT " + msg.req.params.count + ";";
20
21return msg;

Note that we set default of authFilter to 1. It means we’re gonna allow all un-authorized user for now.
Check " AND (" + msg.req.authFilter + ")" + part: If authFilter is 1, this means true, so this query will works normally, but if it’s 0, this means false, so this query will fetch nothing.

Deleting from DB

Note that all the APIs has same structure and procedure; all the differences between them are just ReST API endpoints and DB query.
There are two ways to accomplish this: Recoverable and Permanent.

Recoverable Deletation

Recoverable deletation is just updating value of deleted column to 1.
Since this is just a updating the DB, so i think it’s better to use PATCH HTTP method instead of GET method.

Permanent Deletation

Permanent deletation is deleting the instance inside of DB.
Unlike Recoverable Deletation, i’m decide to use DELETE HTTP method to do it.

Microservice Utilities

ReST/GET Current Timetamp

This functionality coordinates with M2 API.
Set ReST Endpoint to /timestamp, method to GET.
And set function node to:

1msg.payload = {
2    timestamp: (new Date()).getTime().toString()
3};
4return msg;

ReST/GET Random Code

This functionality coordinates with M3 API.
Set ReST Endpoint to /randomcode/:len, method to GET.
- :len represents length of the random code.
And set function node to:

1var randomString = function(length) {
2    var text = "";
3    var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
4    for(var i = 0; i < length; i++) {
5        text += possible.charAt(Math.floor(Math.random() * possible.length));
6    }
7    return text;
8}
9
10msg.payload = {
11    code: randomString(msg.req.params.len)
12};
13
14return msg;

ReST/GET UUID

This functionality coordinates with M4 API.
For this functionality, we have to install node-red-contrib-uuid plugin to generate UUID.
After that, all we have to do is just pass the generated UUID to HTTP response.
So, set ReST Endpoint to /uuid, method to GET.
And set function node to:

1// Prepare response
2msg.payload = {
3    uuid: msg.payload
4};
5
6return msg;

And other…

To implement M5, M6 API, we need to use SendGrid and Twilio.
But to use both of ‘em, we have to pay some money. So, let’s skip these for now.