读DataSnap源代码（三）

function TWebRequestHandler.HandleRequest(Request: TWebRequest;
  Response: TWebResponse): Boolean;
var
  I: Integer;
  LWebModule: TComponent;
  LWebAppServices: IWebAppServices;
  LGetWebAppServices: IGetWebAppServices;
  LComponent: TComponent;
begin
  Result := False;
11   LWebModule := ActivateWebModules;
  if Assigned(LWebModule) then
  try
    try
      if Supports(IInterface(LWebModule), IGetWebAppServices, LGetWebAppServices) then
        LWebAppServices := LGetWebAppServices.GetWebAppServices;
      if LWebAppServices = nil then
        for I := 0 to LWebModule.ComponentCount - 1 do
        begin
          LComponent := LWebModule.Components[I];
          if Supports(LComponent, IWebAppServices, LWebAppServices) then
            if LWebAppServices.Active then
              break
            else
              LWebAppServices := nil;
        end;
      if LWebAppServices = nil then
        LWebAppServices := TDefaultWebAppServices.Create;
      LWebAppServices.InitContext(LWebModule, Request, Response);
      try
        try
          Result := LWebAppServices.HandleRequest;
        except
          ApplicationHandleException(LWebAppServices.ExceptionHandler);
        end;
      finally
        LWebAppServices.FinishContext;
      end;
      if Result and not Response.Sent then
        Response.SendResponse;
    except
      ApplicationHandleException(LWebAppServices.ExceptionHandler);
    end;
  finally
    DeactivateWebModules(LWebModule);
  end;
end;

第11行代码，先得到一个激活的WebModule，如何没有，就会创建一个再返回。

第14行到第26行代码，判断WebModule中是否实现了 IGetWebAppServices 接口的，具体做什么先略过。因为WebModule没有继承这个接口。

第27行，创建一个默认的WebAppServices

第32行，执行默认操作。

function TDefaultWebAppServices.HandleRequest: Boolean;
begin
  Result := InvokeDispatcher;
end;

function TDefaultWebAppServices.InvokeDispatcher: Boolean;
begin
  if RequestHandler <> nil then
  begin
    Result := RequestHandler.HandleRequest(Request, Response);
  end
  else
    raise EWebBrokerException.CreateRes(@sNoDispatcherComponent);
end;

上面的RequestHandler是

    property RequestHandler: IWebRequestHandler read GetRequestHandler;

function TDefaultWebAppServices.GetRequestHandler: IWebRequestHandler;
begin
  if FRequestHandler = nil then
    FRequestHandler := FindRequestHandler;
  Result := FRequestHandler;
end;

function TDefaultWebAppServices.FindRequestHandler: IWebRequestHandler;
var
  Component: TComponent;
begin
  Result := nil;
  Component := FindWebDispatcher;
  if Component <> nil then
    if not Supports(Component, IWebRequestHandler, Result) then
      Assert(False, 'Expect support for IWebRequestHandler');  { do not localize }
end;

function TDefaultWebAppServices.FindWebDispatcher: TComponent;
var
  J: Integer;
begin
  Result := nil;
  if WebModule is TCustomWebDispatcher then
    Result := WebModule
  else
    for J := 0 to WebModule.ComponentCount - 1 do
      if WebModule.Components[J] is TCustomWebDispatcher then
      begin
        Result := WebModule.Components[J];
        break;
      end;
end;

上面红色标记的代码，最终会返回 WebModule.

  TWebModule = class(TCustomWebDispatcher)

所以，上面绿色标记的代码，是调用TCustomWebDispatcher.HandleRequest方法, 内部代码如下：

function TCustomWebDispatcher.HandleRequest(
  Request: TWebRequest; Response: TWebResponse): Boolean;
begin
  FRequest := Request;
  FResponse := Response;
  Result := DispatchAction(Request, Response);
end;