how can i send a post request via Business Central? - dynamics-business-central

Question

I would like to create a PostRequest in my Business Central Extension that authenticates me in my web service and returns me a token. I send my username and password in the body of the request to my web service and I also receive the token in JSON format in the body.I want to create the post request using HttpClient.
I use the following link as a template: https://learn.microsoft.com/en-us/dynamics365/business-central/dev-itpro/developer/methods-auto/httpcontent/httpcontent-data-type
procedure sendPostRequest(uri: Text)
var
client: HttpClient;
content: HttpContent;
contentHeaders: HttpHeaders;
response: HttpResponseMessage;
request: HttpRequestMessage;
begin
content.GetHeaders(contentHeaders);
contentHeaders.Clear();
contentHeaders.Add('Content-Type', 'application/json');
request.Content:= content;
request.SetRequestUri(uri);
request.Method := 'POST';
end;
procedure SetURLsToDefault(var MessagingServiceSetup: Record "Messaging Service Setup WMR")
begin
MessagingServiceSetup."Service URL" := '202.212.127:8800';
end;
And I have a couple of questions:
1) the basic url is 202.212.127:8800 for my API gateway. To be able to authenticate myself I have to access 202.212.127:8800/authenticate. Is there a method in which you can create urls?
2) how do I get my username and password in the content?
3) and how do I get the token and can I save it in the field?
can someone tell me how to get the PostRequest up and running?

Answer 1

Common method to create different URLs is like this:
Create a setup table
Create fields like "Base Url", User, Pass etc.
I propose this pattern for your code:
SendRequest(Method; Url; Body)
Begin
...
Couple of functions (Your Api and Auth):
Authenticate()
begin
Method = 'post';
Url = SetupTable."Base Url" + '/authenticate';
Body = (Use AL Json stack and incorporate your user pass)
SendRequest(Method; Url; Body);
end;
Function1()
begin
Method = 'get';
Url = SetupTable."Base Url" + '/apiPath-Function1';
Body = '';
SendRequest(Method; Url; Body);
end
Function2()
begin
Method = 'post';
Url = SetupTable."Base Url" + '/apiPath-Function2';
Body = (Use AL Json stack and incorporate your body structure);
SendRequest(Method; Url; Body);
end;
To get your user pass into the content you need to check the documentation of the Api you're trying to call. It's usually described in details, it can be a simple header for basic authentication or a complex Jwt.
For receiving a token, again you need to check your Api documentation first, but essentially after making a Rest call (like: client.Send(RequestMessage, ResponseMessage); inside your SendRequest method), you get a response back and you can use AL Json stack to carve information out.
This is a fine article on how to proceed:
https://jackmallender.com/2019/03/04/interacting-with-rest-apis-using-json-from-within-business-central-part-1-an-introduction-to-the-httpclient-data-type/

Answer 2

Basically a string could work as an url. Depends on what you want. It is good practice to have a setup for your web service calls, so I am with Babak. You can set up a table in which you store the links, credentials - whatsoever.
and 4) I suggest Waldos Rest App for web service calls. you can download the source here: https://github.com/waldo1001/waldo.restapp
It encapsulated the calls, has helper functions for json handling as well. Using the "REST Helper" Codeunit. You can break down your call to:
local procedure DoCallWebservice(URI: Text; User: Text; Pass: Text; var Token: Text);
var
RESTHelper: Codeunit "REST Helper WLD";
begin
RRESTHelper.Initialize('GET', URI);
RESTHelper.SetContentType('application/json');
RESTHelper.AddBody('{"user":"USERNAME","pass":"PASSWORD"}');
if RESTHelper.Send() then
Token := RESTHelper.GetResponseContentAsText();
end;
Obviously, you need to parse the response (JSONHelper) to your needs. Look at the code of the codeunit, it's more or less self explanatory.