（2）物件池

 物件池比较简单 ，概念上就是重复使用闲置的无状态元件，避免反复释放/创建，实现也比较简单，就用一个TList就可以了，需要注意的有两个问题：

1、线程同步，Service肯定是多线程的（也有用进程来代替线程的），在存取TList是要用TCriticalSection或别的保护；

2、物件池大小，应该设定一个池大小限制，即池中不需要放太多闲置元件（毕竟是占内存的）；物件总的数量（闲置的加忙碌的）也应该有数量限制，否则可能内存不够，当数量已经满时，如果没有闲置的物件就需要等待，直到有物件闲置下来(可以用信号量来处理)。

线程池是同样的方式。

我觉得无论物件池还是线程池都不是为了效率，物件/线程的创建耗费时间比起你的业务函数执行时间应该小得多，使用池是为了保护有限资源不要被耗尽，设定池的大小来控制资源的使用，否则系统会因为资源不足而拒绝服务或崩溃。

//服务元件池，包括空闲的和忙碌的元件 TServicePool=class private FPool:TStringList; FCritical:TCriticalSection; FDestroying:Boolean; FCheckTimer:TTimer; protected procedure Lock; procedure UnLock; procedure ServiceObjectDestroyed(AServiceObject:TCustomServiceObject); procedure ServiceUnRegistered(AService:TServiceClass); procedure CheckServiceObjectStatus(const AServiceObject:TCustomServiceObject; const AStatus:TServiceObjectStatus); //检查超时调用，超时的调用将被强制停止 procedure CheckServiceTimeOut(Sender:TObject); public constructor Create;virtual; destructor Destroy;override; procedure DestroyIdleObjects;virtual; procedure Clear; //找出一个空闲元件 function Pop(const AServiceName:string;const AServiceObjectStub:integer=-1):TCustomServiceObject; //把元件置为空闲 procedure Push(AServiceObject:TCustomServiceObject); function GetIdleObjectCount(AServiceName:string):integer; function GetBusyObjectCount(AServiceName:string):integer; //回收再利用元件 procedure CycleServiceObject(AServiceObject:TCustomServiceObject); procedure WMApplicationReady(var Msg:TMessage);message WM_ApplicationReady; procedure WMLogout(var Msg:TMessage);message WM_Logout; end;

function TServicePool.Pop(const AServiceName: string; const AServiceObjectStub:integer=-1): TCustomServiceObject;var i,Index:integer; AList:TServiceObjectList; AObject:TCustomServiceObject;begin Result:=nil; Lock; try//还没有元件 if not FPool.Find(AServiceName,Index) then begin AList:=TServiceObjectList.Create(AServiceName); FPool.InsertObject(Index,AServiceName,AList); end else AList:=TServiceObjectList(FPool.Objects[Index]); AObject:=nil;//寻找存根元件 if AServiceObjectStub>0 then begin for i:=0 to AList.Count-1 do begin if Integer(TCustomServiceObject(AList[i]))=AServiceObjectStub then begin AObject:=TCustomServiceObject(AList[i]); break; end; end; if AObject=nil then Raise Exception.CreateFmt(S_StubNotFound,[InttoStr(AServiceObjectStub)]) else if AObject.Status=osBusy then Raise Exception.CreateFmt(S_StubIsBusy,[InttoStr(AServiceObjectStub)]); end else begin//控制池中元件数目（减少一个信号量，等待一个空闲的元件或获得新创建元件的信号）//先解锁，否则可能死锁 UnLock; try AList.WaitFor; finally Lock; end;//寻找一个未锁定的空闲元件 for i:=AList.Count-1 downto 0 do begin if not TCustomServiceObject(AList[i]).FIsLocked and (TCustomServiceObject(AList[i]).Status=osIdle) then begin AObject:=TCustomServiceObject(AList[i]); break; end; end; end;//设置找到元件的状态 if AObject<>nil then begin Result:=AObject; if AObject.Status=osIdle then begin Dec(AList.FIdleCount); Inc(AList.FBusyCount); end; AObject.Status:=osBusy; end; finally UnLock; end; if Result<>nil then begin if ServiceLog<>nil then ServiceLog.ServiceObjectPoolPoped(AServiceName); end;end;procedure TServicePool.Push(AServiceObject: TCustomServiceObject);begin CheckServiceObjectStatus(AServiceObject,osIdle); AServiceObject.FDataObject:=nil;end;procedure TServicePool.CheckServiceObjectStatus(const AServiceObject: TCustomServiceObject; const AStatus:TServiceObjectStatus);var i,Index:integer; AList:TServiceObjectList; AObject:TCustomServiceObject; vFoundObject:Boolean;begin Lock; try AObject:=nil; vFoundObject:=false; if not FPool.Find(AServiceObject.FServiceName,Index) then begin AList:=TServiceObjectList.Create(AServiceObject.FServiceName); FPool.InsertObject(Index,AServiceObject.FServiceName,AList); end else begin AList:=TServiceObjectList(FPool.Objects[Index]); for i:=0 to AList.Count-1 do begin if TCustomServiceObject(AList[i])=AServiceObject then begin AObject:=TCustomServiceObject(AList[i]); vFoundObject:=true; break; end; end; end; if AObject=nil then begin AObject:=AServiceObject; AList.Add(AObject); end;//还原数量 if vFoundObject then begin case AObject.Status of osBusy: begin Dec(AList.FBusyCount);//不用判断是否锁 if (AStatus=osIdle) then begin//增加信号量 AList.Signal; end; end; osIdle: begin Dec(AList.FIdleCount); end; end; end; case AStatus of osBusy: Inc(AList.FBusyCount); osIdle: Inc(AList.FIdleCount); end; AObject.Status:=AStatus; finally UnLock; end; if ServiceLog<>nil then ServiceLog.ServiceObjectPoolPushed(AServiceObject.FServiceName);end;