Question

I have an ISAPI Application in Delphi 6 that uses WebBroker. I need to add logging information at the beggining and the end of each Action.

I have tried OnBeforeDispatch and OnAfterDispatch, but some actions sent the response directly to the browser and the OnAfterDispatch event is never fired.

Is there a way to add a filter or something without having to add code to each action?

Answer 1

One way you can do that is to have only one action. Set the path to “/” and action as default handler. Then:

1. log the start of action
2. From the URL call the appropriate inner handler you specified
3. Log the end of action

I always do an action handler engine that has all actions registered. Then the code is like this

procedure TwmWebModule.wmWebModuleActionHandlerAction(Sender: TObject;
                                                      Request: TWebRequest;
                                                      Response: TWebResponse;
                                                      var Handled: Boolean);
var
  HandlerID: string;
begin
  HandlerID := StringReplace(string(Request.InternalPathInfo), '/', '', []);
  FHandlerEngine.ExecuteHandler(HandlerID, Request, Response);
end;

Now just add logging 🙂 This has other benefits. Every handler is then in its own unit and you achieve the MVC approach of a kind. The code is a lot cleaner and more maintainable.

The skeleton looks like this:

  TCustomHandler = class
  private
    FHandlerID: string;
    FHandlerSettings: ISimpleStorage;
  protected
    procedure Execute(const Request: TWebRequest; const Response: TWebResponse); virtual; abstract;
  public
    constructor Create(const ID: string);
    property HandlerID: string read FHandlerID;
    property HandlerSettings: ISimpleStorage read FHandlerSettings;
  end;

  THandlerEngine = class
  private
    FHandlersList: TObjectList;
    FRegisteredHandlers: THashTable;
  protected
  public
    constructor Create;
    destructor Destroy; override;
    procedure RegisterHandlers;
    procedure AddSingleHandler(const ID: string; const Handler: TCustomHandler);
    procedure ExecuteHandler(const ID: string; const Request: TWebRequest; const Response: TWebResponse);
  end;

You should be able to understand the principle from all this.