（5）Transaction控制

ServiceObject的TransactionMode有三个取值：不需要交易，需要交易，需要新的交易。ServiceObject的方法被调用时会建立一个TTransactionContext，并随着子元件，子子元件的调用传递，子元件，子子元件只是对这个Transaction投票，是需要Commit还是Rollback，根元件根据最后结果来决定最后该Commit还是Rollback。

TCustomServiceObject=class(TObject) private FServiceName:string; FDataObjectCreated:Boolean; //自己使用,每个ServiceObject按需要拥有IDBService FDataObject:TCustomServiceObject; FContext:TTransactionContext; FContextCreated:Boolean; function GetContext: TTransactionContext; procedure LeaveActivity; private FStatus:TServiceObjectStatus; FIsLocked:Boolean; FThreadHandle:THandle; FTimeout:integer; procedure SetStatus(const Value: TServiceObjectStatus); protected procedure Activate;virtual; procedure Deactivate;virtual; function IsCanBePooled:Boolean;virtual; function GetTransactionMode:TServiceTransactionMode;virtual; function GetDataObject: TCustomServiceObject;virtual; function GetDataService: IDBService;virtual; function GetIsInTransaction: Boolean;virtual; function CallMethod(const AMethodName: string; const AParams: OLEVariant; const AAsyncCallContent:TASyncCallContent; const AClientContent:TClientContent):OLEVariant;virtual; public constructor Create(AServiceName:string);virtual; destructor Destroy;override; //调用自己的某个函数 function Call(const AMethodName: string; const AParams: OLEVariant; const AASyncCallContent:TASyncCallContent=nil; const AClientContent:TClientContent=nil): OLEVariant;virtual; //调用其它的元件 function CallOther(const AServiceName,AMethodName:string; const AParams:OLEVariant; const AASyncCallContent:TASyncCallContent=nil; const AClientContent:TClientContent=nil):OLEVariant;virtual; //在activity线程中获得一个服务元件 function BeginUseServiceObject(const AServiceName:string;const AServiceObjectStub:integer=-1):TCustomServiceObject;virtual; //结束activity中的物件使用 procedure EndUseSerivceObject(AService:TCustomServiceObject);virtual; //投票确认activity的交易 procedure VoteCommitTransaction;virtual; //投票拒绝activity的交易 procedure VoteRollbackTransaction;virtual; //某个函数在调用时是否需要记录日志 function IsMethodNeedLog(AMethodName:string):Boolean;virtual; property DataObject:TCustomServiceObject read GetDataObject; property DataService:IDBService read GetDataService; property Context:TTransactionContext read GetContext; property IsInTransaction:Boolean read GetIsInTransaction; property Status:TServiceObjectStatus read FStatus write SetStatus; end; function TCustomServiceObject.Call(const AMethodName: string; const AParams: OLEVariant; const AASyncCallContent:TASyncCallContent=nil; const AClientContent:TClientContent=nil): OLEVariant; const UseDTCTransaction=false; var //单个Connection执行“BEGIN DISTRIBUTED TRANSACTION”并不能将多个Connection纳入分布式事务 IsRoot:Boolean; procedure CheckTransactionStart; begin case GetTransactionMode of tmNeedNew: begin //开始新的activity,这个交易沿新的activity传递 if not FContextCreated then FContext:=nil; //不使用activity传下来的DataOject if not FDataObjectCreated then FDataObject:=nil; if not IsInTransaction then begin if UseDTCTransaction then begin Context.FTransaction:=DTCTransaction.DTCTransactionStart; DataService.JoinDistributeTransaction(Context.FTransaction); end else DataService.StartTransaction; end; end; tmNeed: begin if not IsInTransaction then begin //根元件启动交易 IsRoot:=true; if UseDTCTransaction then begin Context.FTransaction:=DTCTransaction.DTCTransactionStart; DataService.JoinDistributeTransaction(Context.FTransaction); end else DataService.StartTransaction; end; end; end; end; procedure CheckTransactionCommit; begin if GetTransactionMode=tmNeedNew then begin if UseDTCTransaction then DTCTransaction.DTCTransactionCommit(Context.FTransaction) else DataService.CommitTransaction; end else if IsRoot then begin //根元件根据activity的投票结果，决定确认交易还是回滚交易 if Context.FVoteTransactionRollbacked then begin if UseDTCTransaction then DTCTransaction.DTCTransactionRollback(Context.FTransaction) else DataService.RollbackTransaction; end else begin if UseDTCTransaction then DTCTransaction.DTCTransactionCommit(Context.FTransaction) else DataService.CommitTransaction; end; end; //投票确认activity交易 VoteCommitTransaction; end; procedure CheckTransactionRollback; begin if GetTransactionMode=tmNeedNew then begin if IsInTransaction then if UseDTCTransaction then DTCTransaction.DTCTransactionCommit(Context.FTransaction) else DataService.RollbackTransaction; end else if IsRoot then begin if IsInTransaction then if UseDTCTransaction then DTCTransaction.DTCTransactionCommit(Context.FTransaction) else DataService.RollbackTransaction; end; //表决回滚activity的交易 VoteRollbackTransaction; end; procedure CheckClearTransaction; begin if (GetTransactionMode=tmNeedNew) or IsRoot then begin if IsInTransaction then if UseDTCTransaction then DataService.UnJoinDistributeTransaction; ConText.FTransaction:=nil; ConText.FVoteTransactionRollbacked:=false; end; end; var ATime:TDateTime; begin Result:=null; ATime:=Now; if ServiceLog<>nil then ServiceLog.ServiceObjectBeforeMethodCalled(FServiceName,AMethodName); IsRoot:=false; try try CheckTransactionStart; Result:=CallMethod(AMethodName,AParams,AAsyncCallContent,AClientContent); CheckTransactionCommit; except CheckTransactionRollback; Raise; end; finally CheckClearTransaction; if ServiceLog<>nil then ServiceLog.ServiceObjectAfterMethodCalled( FServiceName,AMethodName,Round((Now-ATime)*86400000)); end; end;

如果是多个数据库的分散式Transaction，需要调用MSDTC来控制。

unit DTCTransaction; interface uses SysUtils,OleDB,ComObj,Windows; function DTCTransactionStart:ITransaction; procedure DTCTransactionCommit(ATransaction:ITransaction); procedure DTCTransactionRollback(ATransaction:ITransaction); const TransactionISOLATIONLEVEL=ISOLATIONLEVEL_SERIALIZABLE; CLSID_MSDASQL :TGUID='{C8B522CB-5CF3-11CE-ADE5-00AA0044773D}'; //oledb for ODBC CLSID_SQLOLEDB :TGUID='{0C7FF16C-38E3-11D0-97AB-00C04FC2AD98}'; //oledb for sql server implementation function DtcGetTransactionManager( hostName:PChar; tmName:PChar; iid:Pointer;//pointer of TGUID; dwReserved1:DWord; wReserved2:Word; pvReserved:Pointer; out txnDispenser:ITransactionDispenser):HResult;cdecl;external 'xolehlp.dll'; function DTCTransactionStart:ITransaction; var ID:ITransactionDispenser; begin Result:=nil; OLECheck(DtcGetTransactionManager( nil, nil, @IID_ITransactionDispenser, 0,0, nil, ID)); OLECheck(ID.BeginTransaction(nil, TransactionISOLATIONLEVEL, ISOFLAG_RETAIN_DONTCARE,nil,Result)); end; procedure DTCTransactionCommit(ATransaction:ITransaction); begin OLECheck(ATransaction.Commit(false,0,0)); end; procedure DTCTransactionRollback(ATransaction:ITransaction); var B:BOID; begin OLECheck(ATransaction.Abort(@B,false,false)); end; end.