Delphi DLL

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. Delphi DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
rest: HCkRest;
bAutoReconnect: Boolean;
sbToken: HCkStringBuilder;
topicName: PWideChar;
subscriptionName: PWideChar;
sbPath: HCkStringBuilder;
sbResponseBody: HCkStringBuilder;
message: PWideChar;

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 := CkRest_Create();
bAutoReconnect := True;
success := CkRest_Connect(rest,'<yournamespace>.servicebus.windows.net',443,True,bAutoReconnect);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    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 := CkStringBuilder_Create();
CkStringBuilder_LoadFile(sbToken,'qa_data/tokens/serviceBusSas.txt','utf-8');

// Tell the REST object to use the Azure Shared Access Signature for authorization.
CkStringBuilder_Prepend(sbToken,'SharedAccessSignature ');
CkRest_AddHeader(rest,'Authorization',CkStringBuilder__getAsString(sbToken));

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

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

// Build the path..
sbPath := CkStringBuilder_Create();
CkStringBuilder_Append(sbPath,'/');
CkStringBuilder_Append(sbPath,topicName);
CkStringBuilder_Append(sbPath,'/subscriptions/');
CkStringBuilder_Append(sbPath,subscriptionName);
CkStringBuilder_Append(sbPath,'/messages/head');

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

// Use the DELETE HTTP verb to read the message at the head of the queue and remove it.
sbResponseBody := CkStringBuilder_Create();
success := CkRest_FullRequestNoBodySb(rest,'DELETE',CkStringBuilder__getAsString(sbPath),sbResponseBody);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRest__lastErrorText(rest));
    Exit;
  end;

Memo1.Lines.Add('Response Status Code = ' + IntToStr(CkRest_getResponseStatusCode(rest)));

// Check for a success response.
if (CkRest_getResponseStatusCode(rest) <> 200) then
  begin
    Memo1.Lines.Add(CkRest__lastRequestStartLine(rest));
    Memo1.Lines.Add(CkRest__lastRequestHeader(rest));
    Memo1.Lines.Add(CkStringBuilder__getAsString(sbResponseBody));
    Memo1.Lines.Add('Failed.');
    Exit;
  end;

// If successful, the message is the contents of the response body.
message := CkStringBuilder__getAsString(sbResponseBody);
Memo1.Lines.Add('Received message: ' + message);

Memo1.Lines.Add('Success.');

CkRest_Dispose(rest);
CkStringBuilder_Dispose(sbToken);
CkStringBuilder_Dispose(sbPath);
CkStringBuilder_Dispose(sbResponseBody);

end;