This example will show you how you can implement a Coupa API Client that communicates with your Coupa Core instance using OAuth2 Authorization.
The sample is setup to implement a MemoryCache OAuth Access Token store so it does not have to ask for access token all the time from your Coupa Core instance. This implementation of MemoryCacheTokenStore will expire a cached access token after a certain time. In this example, I am showing you how to expire the access token from cache after 20 hours. See line 32 in Program.cs for how to do this.
The sample is also setup to use the Polly NuGet package and other related helper NuGet packages such as Microsoft.Extensions.Http.Polly and Polly.Contrib.WaitAndRetry to allow communication resiliency upon transient HTTP error/issue. See line 52 in Program.cs for how to do this.
To run this sample, you need .NET 6 or later SDK to be installed. If you are using lower version of .NET, you need to change the .csproj and Program.cs to not use the top level statements. See https://learn.microsoft.com/en-us/dotnet/core/tutorials/top-level-templates for details. You can download .NET 6 SDK from https://dotnet.microsoft.com/en-us/download.
Follow the example on https://success.coupa.com/Integrate/KB/OAuth_2.0_Getting_Started_with_Coupa_API on how to setup your OAuth Client entry in your Coupa Core instance.
IMPORTANT!! You might encounter issue when creating your OAuth Client when following the tutorial in the Coupa Success article above. If you can't see the Secret field, you probably entered the Jwks Uri when setting up the OAuth Client entry. If so, just create another Oauth Client entry but this time, DO NOT enter anything in the Jwks Uri field.
Once you do that, take note (copy & paste) the Identifier and Secret from your Oauth Client entry and paste them into the appropriate places in Program.cs line 12 and 13.
Also, replace line 11 in Program.cs with your Coupa Core instance hostname
Ensure that the Oidc Scopes that you assigned to the OAuth Client entry are also copied (after removing all the commas) into line 14 in Program.cs.
In this sample, I am calling the /api/invoices/{id} where the id is an id of a particular invoice that could be found in the Coupa Core instance. In this case, it is important to have the core.invoice.read Oidc Scope assigned since we are going to read the invoice from that Core instance.
You will want to replace 684 in line 23 of Program.cs with a valid invoice Id on your Coupa Core instance where you know that you have read access to.
Once all of these are done, you can run this sample by typing dotnet run from your terminal/command prompt/bash shell, etc.
When it runs, it should:
- Connect to the Core instance and fetch an OAuth access token, cache it in the
MemoryCacheTokenStore - Fetch the invoice with the specific invoice id and display the
JSONstring of that retrieved invoice.