读DataSnap源代码（六）

具体分析一下DataSanp App与Rest, WebBroker App的不同，先看TDSHTTPService。

***********************************************************************************************

TDSHTTPService = class(TCustomDSHTTPServerTransport)

继承体系：

TDSHTTPService -> TCustomDSHTTPServerTransport -> TCustomDSRESTServerTransport -> TDSServerTransport ...

************************************************************************************************

TDSHTTPWebDispatcher = class(TDSHTTPServerTransport, IWebDispatch)

继承体系：

TDSHTTPWebDispatcher -> TDSHTTPServerTransport -> TCustomDSHTTPServerTransport  ...

************************************************************************************************

都是TCustomDSHTTPServerTransport的后代.  目前来看，如果没有意外，后续的请求处理方式应该是一样的。

那么DataSanp App的WEB请求又是从哪开始的呢？

   TCustomDSHTTPServerTransport = class(TCustomDSRESTServerTransport)
   strict protected
     FHttpServer: TDSHTTPServer;
   strict private
     { Private declarations }
     FCredentialsPassthrough: Boolean;
     FDSAuthPassword: string;
     FDSAuthUser: string;
     FDSPort: Integer;
     FDSHostName: string;
     FDSCacheContext: string;
     function IsCacheContextStored: Boolean;
   private
     function GetHttpServer: TDSHTTPServer;
     function IsDSHostnameStored: Boolean;
     procedure SetCacheContext(const Ctx: string);
     function GetCacheContext: string;
   protected
     function CreateHttpServer: TDSHTTPServer; virtual; abstract;

上面是TCustomDSHTTPServerTransport类的部分定义，可以看到第19行处，有一个abstract的方法，意味着TCustomDSHTTPServerTransport的子类必须实现这个方法 。

 function TDSHTTPService.CreateHttpServer: TDSHTTPServer;
 var
   LHTTPServer: TDSHTTPServerIndy;
 begin
   if Assigned(FCertFiles) then
     LHTTPServer := TDSHTTPSServerIndy.Create(Self.Server, IPImplementationID)
   else
     LHTTPServer := TDSHTTPServerIndy.Create(Self.Server, IPImplementationID);
   Result := LHTTPServer;
   LHTTPServer.HTTPOtherContext := HTTPOtherContext;
 end;

 function TDSHTTPWebDispatcher.CreateHttpServer: TDSHTTPServer;
 begin
   Result := TDSHTTPServerWebBroker.Create;
 end;

果然是不一样的，但都是一个父类继承下来的：

TDSHTTPServerIndy= class(TDSHTTPServer)

TDSHTTPServerWebBroker = class(TDSHTTPServer)

   TDSHTTPServerIndy = class(TDSHTTPServer)
   strict private
     FHTTPOtherContext: TDSHTTPOtherContextEvent;
   private
     FServer: IIPHTTPServer;
     FDefaultPort: Word;
     FServerSoftware: string;
     FIPImplementationID: string;
     FPeerProcs: IIPPeerProcs;
     function PeerProcs: IIPPeerProcs;
     function GetActive: Boolean;
     function GetDefaultPort: Word;
     procedure SetActive(const Value: Boolean);
     procedure SetDefaultPort(const Value: Word);
     procedure DoIndyCommand(AContext: IIPContext;
       ARequestInfo: IIPHTTPRequestInfo; AResponseInfo: IIPHTTPResponseInfo);
     function GetServerSoftware: string;
     procedure SetServerSoftware(const Value: string);
     property HTTPOtherContext: TDSHTTPOtherContextEvent read FHTTPOtherContext write FHTTPOtherContext;
   protected
     function Decode(Data: string): string; override;
     procedure DoCommandOtherContext(AContext: TDSHTTPContext;
       ARequestInfo: TDSHTTPRequest; AResponseInfo: TDSHTTPResponse;
       const ARequest: string); override;
     procedure InitializeServer; virtual;
   public
     constructor Create(const ADSServer: TDSCustomServer; const AIPImplementationID: string = ''); override;
     destructor Destroy; override;
     property Server: IIPHTTPServer read FServer;
     property DefaultPort: Word read GetDefaultPort write SetDefaultPort;
     property Active: Boolean read GetActive write SetActive;
     property ServerSoftware: string read GetServerSoftware write SetServerSoftware;
   end;

 procedure TDSHTTPServerIndy.SetActive(const Value: Boolean);
 begin
   if Value and (FServer = nil) then
   begin
     FServer := PeerFactory.CreatePeer(FIPImplementationID, IIPHTTPServer, nil) as IIPHTTPServer;
     InitializeServer;
   end;
   if FServer <> nil then
     FServer.Active := Value;
 end;