Сеть и HTTP-клиенты

// Один клиент хранит общие настройки и используется для нескольких запросов.
program HttpClientReuse;
{$APPTYPE CONSOLE}
uses System.Net.HttpClient;
var
  Client: THTTPClient;
  Response: IHTTPResponse;
begin
  Client := THTTPClient.Create;
  try
    Client.UserAgent := 'DelphiClient/1';
    Response := Client.Get('https://example.com/api/ping');
    Writeln(Response.StatusCode);
    Response := Client.Get('https://example.com/api/version');
    Writeln(Response.StatusCode);
  finally
    Client.Free;
  end;
end.

// Проследите фактическое поведение RetryPolicy.
program RetryPolicy;
uses System.Net.HttpClient, System.Classes, System.SysUtils;
procedure SendPayment(Client: THTTPClient; const IdempotencyKey: string);
var
  Attempt: Integer;
  Payload: TStringStream;
begin
  Payload := TStringStream.Create('{"amount":100}', TEncoding.UTF8);
  try
    for Attempt := 1 to 3 do
    try
      Payload.Position := 0;
      Client.CustomHeaders['Idempotency-Key'] := IdempotencyKey;
      Client.Post('https://example.com/payments', Payload);
      Exit;
    except
      if Attempt = 3 then raise;
      Sleep(Attempt * 500);
    end;
  finally
    Payload.Free;
  end;
end;
begin end.

// Отделите правило языка от удачного запуска ResponseChecks.
program ResponseChecks;
uses System.Net.HttpClient, System.SysUtils;
procedure ValidateResponse(const R: IHTTPResponse);
var
  Body: string;
begin
  if R.StatusCode <> 200 then
    raise Exception.CreateFmt('HTTP %d', [R.StatusCode]);
  if not R.MimeType.StartsWith('application/json') then
    raise Exception.Create('Unexpected content type');
  Body := R.ContentAsString(TEncoding.UTF8);
  Writeln(Length(Body));
end;
begin end.

// Проследите фактическое поведение StreamDownload.
program StreamDownload;
uses System.Net.HttpClient, System.Classes;
var Client: THTTPClient; FileStream: TFileStream;
begin
  Client := THTTPClient.Create;
  FileStream := TFileStream.Create('package.tmp', fmCreate);
  try
    Client.Get('https://example.com/package.bin', FileStream);
  finally
    FileStream.Free;
    Client.Free;
  end;
end.

// Определите реальную гарантию в TlsValidation.
program TlsValidation;
{$APPTYPE CONSOLE}
function AcceptCertificateDespiteFailure(const FailureReason: string): Boolean;
begin
  Result := True;
end;
begin
  if AcceptCertificateDespiteFailure('hostname mismatch') then
    Writeln('request continues');
end.

// Проследите фактическое поведение HttpTimeout.
program HttpTimeout;
uses System.Net.HttpClient, System.Classes, System.SysUtils;
var
  Client: THTTPClient;
  Payload: TStringStream;
begin
  Client := THTTPClient.Create;
  Payload := TStringStream.Create('{}', TEncoding.UTF8);
  try
    Client.ConnectionTimeout := 5000;
    Client.ResponseTimeout := 15000;
    Client.Post('https://example.com/orders', Payload);
  finally
    Payload.Free;
    Client.Free;
  end;
end.