AL Coding: consume a web service from Dynamics NAV 2018 with POST and Basic Authentication

During our project with Dynamics NAV 2018, we needed to consume a web service from CleverReach (see documentation of their REST API: https://rest.cleverreach.com/howto/), so that we can synchronize the recipients of the newsletters.

Here are now procedures that can be universally useful for using web services from within Dynamics NAV:

See the code at https://github.com/TBits/Al-examples/blob/master/HTTPRequests/cod50131.HttpRequest.al

How to do a simple GET http request:

procedure LoadWebpage(url: Text) result: Text;

How to do a simple POST http request:

procedure PostRequest(url: Text; post_names: List of [Text]; post_values: List of [Text]) result: Text;

And then how to do a POST http request, that is behind Basic Authentication (eg. done with htaccess/htpasswd):

procedure PostRequestWithBasicAuth(
        url: Text;
        post_names: List of [Text];
        post_values: List of [Text];
        username: Text;
        password: Text) result: Text;

I have prepared some web services for testing, see the code in https://github.com/TBits/Al-examples/blob/master/HTTPRequests/pag50130.HttpRequest.al for how to call them.

By the way, this example also shows how to use lists in AL, which is a feature that can hardly be found in the documentation:

var
    post_names: List of [Text];
    i: Integer;
begin
    post_names.Add('test1');
    post_names.Add('test2');
    for i := 1 to post_names.Count do
    begin
        message(post_names.Get(i));
    end;
end;