读DataSnap源代码（二）

program Project1;
{$APPTYPE GUI}

{$R *.dres}

uses
  Vcl.Forms,
  Web.WebReq,
  IdHTTPWebBrokerBridge,
  FormUnit1 in ‘FormUnit1.pas‘ {Form1},
  ServerMethodsUnit1 in ‘ServerMethodsUnit1.pas‘,
  WebModuleUnit1 in ‘WebModuleUnit1.pas‘ {WebModule1: TWebModule};

{$R *.res}

begin{ 返回是什么，见下面的【绿色代码】 }
  if WebRequestHandler <> nil then
    WebRequestHandler.WebModuleClass := WebModuleClass;
  Application.Initialize;
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

IdHTTPWebBrokerBridge单元中：

 1 initialization{** 挂钩 **}
 2   WebReq.WebRequestHandlerProc := IdHTTPWebBrokerBridgeRequestHandler;
 3 {$IFDEF HAS_CLASSVARS}
 4   {$IFNDEF HAS_CLASSDESTRUCTOR}
 5 finalization
 6   FreeAndNil(TIdHTTPWebBrokerBridgeRequestHandler.FWebRequestHandler);
 7   {$ENDIF}
 8 {$ELSE}
 9 finalization
10   FreeAndNil(IndyWebRequestHandler);
11 {$ENDIF}

WebRequestHandler是Web.WebReq中的一个方法：

1 function WebRequestHandler: TWebRequestHandler;
2 begin
3   if Assigned(WebRequestHandlerProc) then
4     Result := WebRequestHandlerProc     /** 指向 IdHTTPWebBrokerBridgeRequestHandler 函数了 **/
5   else
6     Result := nil;
7 end;

IdHTTPWebBrokerBridgeRequestHandler的定义：

 1 function IdHTTPWebBrokerBridgeRequestHandler: TWebRequestHandler;
 2 begin
 3   {$IFDEF HAS_CLASSVARS}
 4   if not Assigned(TIdHTTPWebBrokerBridgeRequestHandler.FWebRequestHandler) then
 5     TIdHTTPWebBrokerBridgeRequestHandler.FWebRequestHandler := TIdHTTPWebBrokerBridgeRequestHandler.Create(nil);
 6   Result := TIdHTTPWebBrokerBridgeRequestHandler.FWebRequestHandler;
 7   {$ELSE}
 8   if not Assigned(IndyWebRequestHandler) then
 9     IndyWebRequestHandler := TIdHTTPWebBrokerBridgeRequestHandler.Create(nil);
10   Result := IndyWebRequestHandler;
11   {$ENDIF}
12 end;

还记得（一）中的那个静态成员吗? 在第4行初始化了。

继续（一）中 Run 函数中的代码：

 1 procedure TIdHTTPWebBrokerBridgeRequestHandler.Run(AThread: TIdContext; ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo);
 2 var
 3   LRequest: TIdHTTPAppRequest;
 4   LResponse: TIdHTTPAppResponse;
 5 begin
 6   try
 7     LRequest := TIdHTTPAppRequest.Create(AThread, ARequestInfo, AResponseInfo);
 8     try
 9       LResponse := TIdHTTPAppResponse.Create(LRequest, AThread, ARequestInfo, AResponseInfo);
10       try
11         // WebBroker will free it and we cannot change this behaviour
12         AResponseInfo.FreeContentStream := False;
13         HandleRequest(LRequest, LResponse);
14       finally
15         FreeAndNil(LResponse);
16       end;
17     finally
18       FreeAndNil(LRequest);
19     end;
20   except
21     // Let Indy handle this exception
22     raise;
23   end;
24 end;

TIdHTTPWebBrokerBridgeRequestHandler并没有 override 父类(TWebRequestHandler)的HandleRequest方法. 看TWebRequestHandler.HandleRequest代码

 1 function TWebRequestHandler.HandleRequest(Request: TWebRequest;
 2   Response: TWebResponse): Boolean;
 3 var
 4   I: Integer;
 5   LWebModule: TComponent;
 6   LWebAppServices: IWebAppServices;
 7   LGetWebAppServices: IGetWebAppServices;
 8   LComponent: TComponent;
 9 begin
10   Result := False;
11   LWebModule := ActivateWebModules;
12   if Assigned(LWebModule) then
13   try
14     try
15       if Supports(IInterface(LWebModule), IGetWebAppServices, LGetWebAppServices) then
16         LWebAppServices := LGetWebAppServices.GetWebAppServices;
17       if LWebAppServices = nil then
18         for I := 0 to LWebModule.ComponentCount - 1 do
19         begin
20           LComponent := LWebModule.Components[I];
21           if Supports(LComponent, IWebAppServices, LWebAppServices) then
22             if LWebAppServices.Active then
23               break
24             else
25               LWebAppServices := nil;
26         end;
27       if LWebAppServices = nil then
28         LWebAppServices := TDefaultWebAppServices.Create;
29       LWebAppServices.InitContext(LWebModule, Request, Response);
30       try
31         try
32           Result := LWebAppServices.HandleRequest;
33         except
34           ApplicationHandleException(LWebAppServices.ExceptionHandler);
35         end;
36       finally
37         LWebAppServices.FinishContext;
38       end;
39       if Result and not Response.Sent then
40         Response.SendResponse;
41     except
42       ApplicationHandleException(LWebAppServices.ExceptionHandler);
43     end;
44   finally
45     DeactivateWebModules(LWebModule);
46   end;
47 end;

在上面代码中，可以看到 WebModule 字眼了， ：）