How to use the OMNIA Platform's API, using Swagger

1. Introduction

In the third release of the OMNIA Platform, the API and its usage were two of our main concerns. This version provides a clear API that has all of the functionality and doesn’t require the clients to implement logic.

The OMNIA API was implemented together respecting the OpenAPI Specification. This means that, with the use of OpenAPI file generated with Swagger, it is possible to:

  • Generate API clients for whichever languages users want to use to develop software that requires our API;
  • Generate interactive documentation automatically, using Swagger UI.

2. Using Swagger UI

By accessing the Swagger UI page hosted at /api/docs/ (i.e. if your subscription of the platform is installed at omnia.example.com, omnia.example.com/api/docs/), you will see all of the possible options for interacting with the platform via the API.

We are actively working on enriching this API documentation with more and better examples of the information to be sent in different scenarios.

Usage guidelines:

  • Authorization is required to access almost every method in our API. Swagger UI provides an Authorize button that allows you to perform an authorization operation.
  • To use a method, after selecting it and seeing the documentation, you can click the Try it out button and Swagger will open a series of fields you can type your information into, and an Execute button.
  • All updates to existing resources use the HTTP PATCH method and implement the JSONPatch standard.

    In order to calculate the patch between the current state and the state you want it to be in, there are a number of tools, such as JSON Patch Builder Online.

3. Consuming the API with an API Client

It’s possible to use whatever language you want to access the OMNIA API, allowing you to use the API the way you need to.

Our API requires authorization, so the first you need to do is register an API client in the platform (see here how).

We choose OAuth 2.0 as our authorization protocol. OAuth 2.0 is the industry-standard protocol for authorization and securing access to APIs with focus on client developer simplicity.

After the register, using the generated Client ID and Client Secret, you are able to request an access token to gain access to the API, through the OAuth 2.0 Client Credentials flow, and start using the API.

3.1 Request an access token using C#

Requesting an access token can be easy using IdentityModel an OpenID Connect & OAuth 2.0 client library.

using IdentityModel.Client;

string accessToken = null;

// discover endpoints from metadata
var discoveryClient = new DiscoveryClient("[Identity Endpoint]") 
{ 
	//Policy = { RequireHttps = false } //uncomment the Policy property if you use a insecure connection
};
var discoEndpoint = await discoveryClient.GetAsync();
if (!discoEndpoint.IsError)
{
    //request token
    var tokenClient = new TokenClient(discoEndpoint.TokenEndpoint, userId, "[Your secret]");
    var tokenResponse = await tokenClient.RequestClientCredentialsAsync("[Required scopes]");

    if (!tokenResponse.IsError)
    {
        accessToken = tokenResponse.AccessToken;
    }
}

As you can see in the previous example, when a token is requested, the scope must be sent. Currently, OMNIA platform supports only one scope, named api. This is the scope required to access OMNIA API.

3.2 Using HttpClient to send request to the API

Using the built-in .NET HttpClient, you can use the requested token to perform requests to our API.

using System.Collections.Generic;
using System.Net.Http;

var authHeaderValue = new AuthenticationHeaderValue("Bearer", "[Access Token]");
var client = new HttpClient() { DefaultRequestHeaders = { Authorization = authHeaderValue } };

var requestResponse = await client.GetAsync("[API Endpoint]}");
if (requestResponse.IsSuccessStatusCode)
{
    var responseBody = await requestResponse.Content.ReadAsStringAsync();
	var response = JsonConvert.DeserializeObject<Dictionary<string, object>>(responseBody);
}