Pascal (Lazarus/Delphi)

Azure Service Bus - Delete Message

See more Azure Service Bus Examples

Deletes a message from a queue or subscription.

For more information, see https://docs.microsoft.com/en-us/rest/api/servicebus/unlock-message

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;
  messageId: string;
  lockToken: string;
  sbPath: TStringBuilder;
  numReplaced: Integer;
  sbResponseBody: TStringBuilder;

begin
  success := False;

  //  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;

  //  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());

  //  ----------------------------------------------------------------------------------------------
  //  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..
  //  ----------------------------------------------------------------------------------------------

  //  To delete a message, we'll need either the SequenceNumber or MessageId.
  //  When the message was peek-locked, the SequenceNumber and MessageId of the locked message
  //  was returned in the HTTP response header named "BrokerProperties, which contained
  //  JSON such as the following:
  //  
  //  	{
  //  	  "DeliveryCount": 1,
  //  	  "EnqueuedSequenceNumber": 3000004,
  //  	  "EnqueuedTimeUtc": "Wed, 07 Dec 2016 17:42:48 GMT",
  //  	  "Label": "M3",
  //  	  "LockToken": "6eeee205-e541-4cb6-95fb-4c81da5f6858",
  //  	  "LockedUntilUtc": "Thu, 08 Dec 2016 00:57:32 GMT",
  //  	  "MessageId": "e8028116d63c43f191577f2789b1cca7",
  //  	  "SequenceNumber": 4,
  //  	  "State": "Active",
  //  	  "TimeToLive": 922337193600
  //  	}
  //  
  //  
  //  The path for unlocking a message is constructed as follows, depending on
  //  whether it is a message on a queue or subscription:
  //  
  //  (for a queue)
  //  /{queuePath}/messages/{messageId|sequenceNumber}/{lockToken}
  //  
  //  (for a subscription)
  //  /{topicPath}/subscriptions/{subscriptionName}/messages/{messageId|sequenceNumber}/{lockToken}

  //  This example will build a path to delete a message contained in a subscription.
  topicName := 'gilaMonster';
  subscriptionName := 'feedings';
  messageId := 'e8028116d63c43f191577f2789b1cca7';
  lockToken := '6eeee205-e541-4cb6-95fb-4c81da5f6858';

  //  Build the path..
  sbPath := TStringBuilder.Create;
  sbPath.Append('/{topicPath}/subscriptions/{subscriptionName}/messages/{messageId|sequenceNumber}/{lockToken}');
  numReplaced := sbPath.Replace('{topicPath}',topicName);
  numReplaced := sbPath.Replace('{subscriptionName}',subscriptionName);
  numReplaced := sbPath.Replace('{messageId|sequenceNumber}',messageId);
  numReplaced := sbPath.Replace('{lockToken}',lockToken);

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

  //  Use the DELETE HTTP verb to delete the message.
  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 response body would be empty..
  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.