Pascal (Lazarus/Delphi)

Lower-Level REST API Methods (Google Cloud Storage)

See more REST Examples

The FullRequest* methods, such as FullRequestBinary, FullRequestMultipart, FullRequestNoBody, FullRequestStream, FullRequestString, etc. are high-level REST API methods that both send the request and receive the response. It is often the case that an application needs make a REST call, but with a finer level of control. The Chilkat REST API provides this feature. An application can break a REST call into the following parts:

1. Send the HTTP request. (via the SendReq* methods)
2. Receive the HTTP response header. (ReadResponseHeader)
3. Receive the HTTP response body. (via the ReadRespBody* methods)

This example demonstrates a REST call using SendReqStringBody, ReadResonseHeader, and ReadRespBodyString.

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.AuthGoogle,
  Chilkat.JsonObject,
  Chilkat.Rest;

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

procedure RunDemo;
var
  success: Boolean;
  gAuth: TAuthGoogle;
  rest: TRest;
  bAutoReconnect: Boolean;
  jsonReqBody: TJsonObject;
  objVersioning: TJsonObject;
  responseStatusCode: Integer;
  responseBodyStr: string;

begin
  success := False;

  //  This example demonstrates a REST call using SendReqStringBody, ReadResonseHeader, and ReadRespBodyString.
  //  It will create a bucket in Google Cloud Storage.

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

  gAuth := TAuthGoogle.Create;
  //  Obtain an access token as shown in one of the following examples:
  //  See Get Access Token using a Service Account JSON Key
  //  See Get Access Token using a P12 File

  rest := TRest.Create;

  //  Connect using TLS.
  bAutoReconnect := True;
  success := rest.Connect('www.googleapis.com',443,True,bAutoReconnect);

  //  Provide the authentication credentials (i.e. the access key)
  success := rest.SetAuthGoogle(gAuth);

  //  Build the JSON request body for creating a bucket.
  //  The only required property is the "name", but we'll add more
  //  to make a better example..
  jsonReqBody := TJsonObject.Create;
  success := jsonReqBody.AddStringAt(-1,'name','chilkat-bucket-c');
  success := jsonReqBody.AddStringAt(-1,'kind','storage#bucket');
  success := jsonReqBody.AddStringAt(-1,'location','US');

  objVersioning := TJsonObject.Create;
  jsonReqBody.AppendObject2('versioning',objVersioning);
  success := objVersioning.AddBoolAt(-1,'enabled',True);

  //  Show the HTTP request body we'll be sending.
  WriteLn(jsonReqBody.Emit());

  //  Add the required query parameter.
  //  See https://cloud.google.com/storage/docs/json_api/v1/buckets/insert
  success := rest.AddQueryParam('project','chilkattest-1050');

  //  Add the Content-Type HTTP request header.
  success := rest.AddHeader('Content-Type','application/json; charset=UTF-8');

  //  Send the REST HTTP request.
  success := rest.SendReqStringBody('POST','/storage/v1/b',jsonReqBody.Emit());
  if (success = False) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

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

  if (responseStatusCode <> 200) then
    begin
      //  The response was not successful.  We'll still need to receive 
      //  the response body, which may contain an error message from the server.
      //  If the response has no body, then the method for reading the
      //  response body can still be called.  It will simply return with an empty
      //  response body.

      //  We can examine the response header and status text:
      WriteLn('Response status text: ' + rest.ResponseStatusText);
      WriteLn('Response header: ' + rest.ResponseHeader);
    end;

  //  Read the response body.  In this case we're expecting it to be JSON..
  responseBodyStr := rest.ReadRespBodyString();
  if (rest.LastMethodSuccess <> True) then
    begin
      //  We were unable to receive the response body.
      //  Note: If the response did not include a body (such as for cases where
      //  the Content-Length header is 0, or if the response status code implicitly
      //  indicates no body, then ReadRespBodyString returns cktrue, and the
      //  responseBodyString will be an empty string.
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  Show the JSON response.
  WriteLn('Json Response: ' + responseBodyStr);


  gAuth.Free;
  rest.Free;
  jsonReqBody.Free;
  objVersioning.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.