Pascal (Lazarus/Delphi)

REST Read Response with Stream API

See more REST Examples

Demonstrates how to make a REST call that returns a binary body, and to receive the body through a stream API. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.AuthAws,
  Chilkat.Rest,
  Chilkat.Task,
  Chilkat.Stream;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  rest: TRest;
  bTls: Boolean;
  port: Integer;
  bAutoReconnect: Boolean;
  authAws: TAuthAws;
  responseStatusCode: Integer;
  errResponse: string;
  bodyStream: TStream;
  readResponseBodyTask: TTask;
  nextChunk: TBytes;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  rest := TRest.Create;

  //  Connect to the Amazon AWS REST server.
  bTls := True;
  port := 443;
  bAutoReconnect := True;
  success := rest.Connect('s3.amazonaws.com',port,bTls,bAutoReconnect);

  //  ----------------------------------------------------------------------------
  //  Important: For buckets created in regions outside us-east-1,
  //  there are three important changes that need to be made.
  //  See Working with S3 Buckets in Non-us-east-1 Regions for the details.
  //  ----------------------------------------------------------------------------

  //  Provide AWS credentials for the REST call.
  authAws := TAuthAws.Create;
  authAws.AccessKey := 'AWS_ACCESS_KEY';
  authAws.SecretKey := 'AWS_SECRET_KEY';
  authAws.ServiceName := 's3';
  success := rest.SetAuthAws(authAws);

  //  Set the bucket name via the HOST header.
  //  In this case, the bucket name is "chilkat100".
  rest.Host := 'chilkat100.s3.amazonaws.com';

  //  Send the request to download the JPG.
  success := rest.SendReqNoBody('GET','/starfish.jpg');
  if (success <> True) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  Read the response header.
  responseStatusCode := rest.ReadResponseHeader();
  if (responseStatusCode < 0) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  WriteLn('Response status code = ' + responseStatusCode);

  //  We expect a 200 response status if the JPG data is coming.
  //  Otherwise, we'll get a string response body with an error message(or no response body).
  if (responseStatusCode <> 200) then
    begin
      errResponse := rest.ReadRespBodyString();
      if (rest.LastMethodSuccess <> True) then
        begin
          WriteLn(rest.LastErrorText);
        end
      else
        begin
          WriteLn(errResponse);
        end;
      Exit;
    end;

  bodyStream := TStream.Create;
  //  Set a 10 second read timeout for the stream. 
  //  (Give up if no data arrives within 10 seconds after calling a read method.)
  bodyStream.ReadTimeoutMs := 10000;

  //  Create a background thread task to read the response body (which feeds
  //  it to the bodyStream object.)
  readResponseBodyTask := rest.ReadRespBodyStreamAsync(bodyStream,True);

  //  Start the task. 
  success := readResponseBodyTask.Run();

  //  The application can now read the bodyStream...
  while (bodyStream.EndOfStream <> True) do
    begin

      //  Read the next chunk of bytes (whatever is immediately available,
      //  or wait for more data (up to 10 seconds because we set the stream's ReadTimeoutMs property)
      nextChunk := bodyStream.ReadBytes();
      if (bodyStream.LastMethodSuccess <> True) then
        begin
          WriteLn('Failed to receive more response data.');
          //  Make sure the background task is aborted/cancelled.
          success := readResponseBodyTask.Cancel();
          readResponseBodyTask.Free;
          Exit;
        end;

      //  OK.. the app has the next chunk of the body, and may do whatever it wishes with it...
    end;

  readResponseBodyTask.Free;

  WriteLn('Successfully received the entire response body.');


  rest.Free;
  authAws.Free;
  bodyStream.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.