Pascal (Lazarus/Delphi)

Azure Service Bus - Receive and Delete Message from Subscription

See more Azure Service Bus Examples

Shows how to receive and delete a message from an Azure service bus topic subscription. 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.Rest,
  Chilkat.StringBuilder;

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

procedure RunDemo;
var
  success: Boolean;
  rest: TRest;
  bAutoReconnect: Boolean;
  sbToken: TStringBuilder;
  topicName: string;
  subscriptionName: string;
  sbPath: TStringBuilder;
  sbResponseBody: TStringBuilder;
  message: string;

begin
  success := False;

  //  Note: Requires Chilkat v9.5.0.65 or greater.

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

  //  Make the initial connection.
  //  A single REST object, once connected, can be used for many Azure Service Bus REST API calls.
  //  The auto-reconnect indicates that if the already-established HTTPS connection is closed,
  //  then it will be automatically re-established as needed.
  rest := TRest.Create;
  bAutoReconnect := True;
  success := rest.Connect('<yournamespace>.servicebus.windows.net',443,True,bAutoReconnect);
  if (success <> True) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  //  ----------------------------------------------------------------------------------------------
  //  The code above this comment could be placed inside a function/subroutine within the application
  //  because the connection does not need to be made for every request.  Once the connection is made
  //  the app may send many requests..
  //  ----------------------------------------------------------------------------------------------

  //  Let's load a previously computed SAS token and use it.
  //  See Azure Shared Access Signature for an example to genenerate an Azure SAS token.
  sbToken := TStringBuilder.Create;
  sbToken.LoadFile('qa_data/tokens/serviceBusSas.txt','utf-8');

  //  Tell the REST object to use the Azure Shared Access Signature for authorization.
  sbToken.Prepend('SharedAccessSignature ');
  rest.AddHeader('Authorization',sbToken.GetAsString());

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

  //  Receive a message from the subscription "feedings" in the topic "gilaMonster"
  topicName := 'gilaMonster';
  subscriptionName := 'feedings';

  //  Build the path..
  sbPath := TStringBuilder.Create;
  sbPath.Append('/');
  sbPath.Append(topicName);
  sbPath.Append('/subscriptions/');
  sbPath.Append(subscriptionName);
  sbPath.Append('/messages/head');

  //  Add a timeout parameter.
  rest.AddQueryParam('timeout','20');

  //  Use the DELETE HTTP verb to read the message at the head of the queue and remove it.
  sbResponseBody := TStringBuilder.Create;
  success := rest.FullRequestNoBodySb('DELETE',sbPath.GetAsString(),sbResponseBody);
  if (success <> True) then
    begin
      WriteLn(rest.LastErrorText);
      Exit;
    end;

  WriteLn('Response Status Code = ' + rest.ResponseStatusCode);

  //  Check for a success response.
  if (rest.ResponseStatusCode <> 200) then
    begin
      WriteLn(rest.LastRequestStartLine);
      WriteLn(rest.LastRequestHeader);
      WriteLn(sbResponseBody.GetAsString());
      WriteLn('Failed.');
      Exit;
    end;

  //  If successful, the message is the contents of the response body.
  message := sbResponseBody.GetAsString();
  WriteLn('Received message: ' + message);

  WriteLn('Success.');


  rest.Free;
  sbToken.Free;
  sbPath.Free;
  sbResponseBody.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.