(Delphi DLL) Lower-Level REST API Methods (Google Cloud Storage)

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.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, AuthGoogle, JsonObject, Rest;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
gAuth: HCkAuthGoogle;
rest: HCkRest;
bAutoReconnect: Boolean;
jsonReqBody: HCkJsonObject;
pObjVersioning: HCkJsonObject;
responseStatusCode: Integer;
responseBodyStr: PWideChar;

begin
// 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 := CkAuthGoogle_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 := CkRest_Create();

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

// Provide the authentication credentials (i.e. the access key)
success := CkRest_SetAuthGoogle(rest,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 := CkJsonObject_Create();
success := CkJsonObject_AddStringAt(jsonReqBody,-1,'name','chilkat-bucket-c');
success := CkJsonObject_AddStringAt(jsonReqBody,-1,'kind','storage#bucket');
success := CkJsonObject_AddStringAt(jsonReqBody,-1,'location','US');
success := CkJsonObject_AddObjectAt(jsonReqBody,-1,'versioning');

pObjVersioning := CkJsonObject_ObjectOf(jsonReqBody,'versioning');
success := CkJsonObject_AddBoolAt(pObjVersioning,-1,'enabled',True);
CkJsonObject_Dispose(pObjVersioning);

// Show the HTTP request body we'll be sending.
Memo1.Lines.Add(CkJsonObject__emit(jsonReqBody));

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

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

// Send the REST HTTP request.
success := CkRest_SendReqStringBody(rest,'POST','/storage/v1/b',CkJsonObject__emit(jsonReqBody));
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

// Read the response header.
responseStatusCode := CkRest_ReadResponseHeader(rest);
if (responseStatusCode < 0) then
  begin
    // We were unable to receive the response header.
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    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:
    Memo1.Lines.Add('Response status text: ' + CkRest__responseStatusText(rest));
    Memo1.Lines.Add('Response header: ' + CkRest__responseHeader(rest));
  end;

// Read the response body.  In this case we're expecting it to be JSON..
responseBodyStr := CkRest__readRespBodyString(rest);
if (CkRest_getLastMethodSuccess(rest) <> 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.
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

// Show the JSON response.
Memo1.Lines.Add('Json Response: ' + responseBodyStr);

CkAuthGoogle_Dispose(gAuth);
CkRest_Dispose(rest);
CkJsonObject_Dispose(jsonReqBody);

end;