后续行动（2014年4月9日）：用DOA 4.1.1替换DOA 4.0.7.1后，我无法重复此问题。我的问题已被弃用！但是，我仍然有兴趣收到任何在生产软件中实现了TOracleEvent的人的反馈。
原始问题：
如何使用DOA 4.0.7在Delphi 6中可靠地实现DBMS_ALERT的TOracleEvent？
或
如何在不破坏DOA源代码的情况下解决TOracleEvent.Stop方法锁定问题？
如果可能的话，我更喜欢修复或解决方法，而不需要修改原始的AllRoundAutomations DOA源代码。
我正在使用传统的Delphi 6和AllRoundAutomations Direct Oracle Access DOA 4.0.7。我已经点击了一个show stop，DOA TOracleEvent实例无法停止和释放，因此应用程序的进程无法自行终止。
我对DOA文档的理解是我应该调用myOracleEvent.Stop（）来清理TOracleEvent实例。但是，如果我执行Stop（）方法，我的应用程序将“挂起”该方法调用。如果我没有调用Stop（），我的应用程序将关闭，但它的进程将无限期地保持活着，直到我用taskmanager或其他方式杀死它。
TOracleEvent可以管理两种类型的信号：dbms_alert和管道。我正在使用dbms_alert信号来启用多个接收器。
在AllRoundAutomations论坛上搜索此问题时发现其他一些人遇到过此问题，但我没有找到任何答案。
我不认为这是Oracle服务器端问题，因为Application的TOracleEvent进程导致了阻塞。也就是说，TOracleEvent实例不是“等待”任何东西，它只是挂起。如果我杀掉“挂起”的Oracle会话服务器端，它就不会被释放。当然，问题可能是我的程序没有正确配置TOracleEvent属性或正确清理它以进行处理。
以下是用于测试用例状态机的Delphi-6代码，它隔离了DOA.TOracleEvent.Stop（）方法冻结的问题。如果修复了TOracleEvent.Stop（），那么状态机应该显示类似于下面代码后面显示的结果。如果没有修复，Stop（）方法将在调用时冻结。如果不修复（黑客攻击）DOA源代码，我无法使任何小型测试应用程序可靠地工作。
implementation
{$R *.dfm}
const
ALERT_NAME__STACKOVERFLOW = 'STACKOVERFLOW';
/// This is the TOracleEvent.OnEvent handler that listens for DBMS_ALERT Signals.
procedure TForm1.OracleEvent1Event(Sender: TOracleEvent; const ObjectName: String; const Info: Variant);
var
ii: integer;
begin
Memo1.Lines.Add('*> Oracle Event Received!');
Memo1.Lines.Add(' DBMS_ALERT.SIGNAL name = ' + ObjectName);
if VarIsArray(Info) then begin
for ii := 0 to VarArrayHighBound(Info, 1) do begin
Memo1.Lines.Add(' Message= ' + Info[ii]);
end;
end;
Memo1.Refresh();
end;
procedure TForm1.btnRunStateMachineClick(Sender: TObject);
begin
// Button clicked to clear the display and start the state machine timer.
AppState := 0;
Memo1.Lines.Clear();
Timer1.Enabled := true;
end;
procedure TForm1.Timer1Timer(Sender: TObject);
begin
// Time Interval State Machine that steps through the test sequence.
// Stop the Timer for Failsafe
Timer1.Enabled := false;
if (AppState = 0) then begin
try
Memo1.Lines.Add('==========================');
Memo1.Lines.Add('Connecting OracleSession2 to DB ...');
// Check for, Close, and Destroy previous Sessions
if (Assigned(OracleSession2) and OracleSession2.Connected) then begin
// Close the Connection
OracleSession2.LogOff();
OracleSession2.Connected := false;
OracleSession2.Free();
OracleSession2 := nil;
end;
if (not Assigned(OracleSession2)) then begin
OracleSession2 := TOracleSession.Create(self);
end;
// Configure Session #2 for general purpose routines
OracleSession2.LogonDatabase := 'STACKOVERFLOW_DB';
OracleSession2.LogonPassword := 'drowssap';
OracleSession2.LogonUserName := 'answer';
OracleSession2.Pooling := spInternal;
OracleSession2.ThreadSafe := true;
OracleSession2.Connected := true;
Memo1.Lines[Memo1.Lines.Count - 1] := 'DB OracleSession2 Connected!';
Inc(AppState);
except
on ex0: Exception do begin
AppState := -1;
Memo1.Lines.Add('!! ERROR !! ' + ex0.Message);
end;
end;
end
else if (AppState = 1) then begin
try
Memo1.Lines.Add('Connecting OracleSession1 to DB ...');
if (Assigned(OracleSession1) and OracleSession1.Connected) then begin
OracleSession1.LogOff();
OracleSession1.Connected := false;
OracleSession1.Free();
OracleSession1 := nil;
end;
if (not Assigned(OracleSession1)) then begin
OracleSession1 := TOracleSession.Create(self);
end;
// Configure Session #1 for the OracleEvent Handler
OracleSession1.LogonDatabase := 'STACKOVERFLOW_DB';
OracleSession1.LogonPassword := 'drowssap';
OracleSession1.LogonUserName := 'answer';
OracleSession1.Pooling := spInternal;
OracleSession1.ThreadSafe := true;
OracleSession1.Connected := true;
Memo1.Lines[Memo1.Lines.Count - 1] := 'DB OracleSession1 Connected!';
Inc(AppState);
except
on ex1: Exception do begin
AppState := -1;
Memo1.Lines.Add('!! ERROR !! ' + ex1.Message);
end;
end;
end
else if (AppState = 2) then begin
try
Memo1.Lines.Add('Configuring the Oracle Event Handler ...');
if (not OracleEvent1.Started) then begin
if (OracleEvent1.Session = nil) then begin
OracleEvent1.Session := OracleSession1;
end;
OracleEvent1.KeepConnection := false;
OracleEvent1.Synchronized := true;
OracleEvent1.TimeOut := 1;
OracleEvent1.ObjectNames := ALERT_NAME__STACKOVERFLOW;
OracleEvent1.Start();
Memo1.Lines[Memo1.Lines.Count -1] := 'Oracle Event Handler Started!';
end;
Inc(AppState);
except
on ex2: Exception do begin
AppState := -1;
Memo1.Lines.Add('!! ERROR !! ' + ex2.Message);
end;
end;
end
else if ((AppState >= 3) and (AppState <= 7)) then begin
try
Memo1.Lines.Add('Sending a DBMS_ALERT Signal to StackOverflow ...');
try
OracleSession1.DBMS_Alert.Signal(ALERT_NAME__STACKOVERFLOW, 'Hello StackOverflow! ' + FormatDateTime('HH:nn:ss', now));
OracleSession1.Commit();
except
on ex: Exception do begin
Memo1.Lines.Add('*> Oracle Event Signal ERRORT!');
Memo1.Lines.Add(ex.Message);
end;
end;
Inc(AppState);
except
on ex3: Exception do begin
AppState := -1;
Memo1.Lines.Add('!! ERROR !! ' + ex3.Message);
end;
end;
end
else if (AppState = 8) then begin
try
Memo1.Lines.Add('Disconnecting OracleSession2 from DB ...');
if (Assigned(OracleSession2) and OracleSession2.Connected) then begin
OracleSession2.LogOff();
OracleSession2.Connected := false;
OracleSession2.Free();
OracleSession2 := nil;
end;
Memo1.Lines[Memo1.Lines.Count -1] := 'DB OracleSession2 Disconnected!';
Inc(AppState);
except
on ex4: Exception do begin
AppState := -1;
Memo1.Lines.Add('!! ERROR !! ' + ex4.Message);
end;
end;
end
else if (AppState = 9) then begin
try
Memo1.Lines.Add('Stopping OracleEvent handler.');
Memo1.Lines.Add(' * THIS IS WHERE THE HANGUP PROBLEM IS CALLED!');
OracleEvent1.Stop(); // <<<< Freezes here if TOracleEvent.Stop() is not fixed!
////
Memo1.Lines.Add('OracleEvent Handler Stopped OK!');
Memo1.Lines.Add(' * If we got here, either there were no events...');
Memo1.Lines.Add(' or the Bug is Fixed B-)');
Inc(AppState);
except
on ex5: Exception do begin
AppState := -1;
Memo1.Lines.Add('!! ERROR !! ' + ex5.Message);
end;
end;
end
else if (AppState = 10) then begin
try
Memo1.Lines.Add('Disconnecting OracleSession1 from DB ...');
if (Assigned(OracleSession1) and OracleSession1.Connected) then begin
OracleSession1.LogOff();
OracleSession1.Connected := false;
OracleSession1.Free();
OracleSession1 := nil;
end;
Memo1.Lines[Memo1.Lines.Count -1] := 'DB OracleSession1 Disconnected!';
Inc(AppState);
except
on ex6: Exception do begin
AppState := -1;
Memo1.Lines.Add('!! ERROR !! ' + ex6.Message);
end;
end;
end
else begin
AppState := 0;
end;
Memo1.Refresh();
Timer1.Enabled := (AppState >= 0);
end;
procedure TForm1.btnStopClick(Sender: TObject);
begin
// Stop Button Clicked to halt the State Machine
Timer1.Enabled := false;
Memo1.Lines.Add('State Machine Stopped.');
Memo1.Refresh();
end;
/// Other handlers on the TOracleEvent instance
procedure TForm1.OracleEvent1Start(Sender: TOracleEvent);
begin
Memo1.Lines.Add('*> Oracle Event START!');
end;
procedure TForm1.OracleEvent1Stop(Sender: TOracleEvent);
begin
Memo1.Lines.Add('*> Oracle Event STOP!');
end;
procedure TForm1.OracleEvent1Error(Sender: TOracleEvent; const Error: Exception);
begin
Memo1.Lines.Add('*> Oracle Event ERROR!');
Memo1.Lines.Add('=> ' + Error.Message);
end;
procedure TForm1.OracleEvent1TimeOut(Sender: TOracleEvent; var Continue: Boolean);
begin
Memo1.Lines.Add('*> Oracle Event TIMEOUT!');
end;
以下是状态机的输出：
==========================
The following are the results for successfully running
the state machine with a DOA.TOracleEvent.Stop() "fixed".
Without fixing DOA.TOracleEvent.Stop(), the state machine will "freeze"
==========================
DB OracleSession2 Connected!
DB OracleSession1 Connected!
Configuring the Oracle Event Handler ...
Oracle Event Handler Started!
Sending a DBMS_ALERT Signal to StackOverflow ...
*> Oracle Event Received!
DBMS_ALERT.SIGNAL name = STACKOVERFLOW
Message= Hello StackOverflow! 21:55:41
*> Oracle Event TIMEOUT!
Sending a DBMS_ALERT Signal to StackOverflow ...
*> Oracle Event Received!
DBMS_ALERT.SIGNAL name = STACKOVERFLOW
Message= Hello StackOverflow! 21:55:42
*> Oracle Event TIMEOUT!
Sending a DBMS_ALERT Signal to StackOverflow ...
*> Oracle Event Received!
DBMS_ALERT.SIGNAL name = STACKOVERFLOW
Message= Hello StackOverflow! 21:55:43
*> Oracle Event TIMEOUT!
Sending a DBMS_ALERT Signal to StackOverflow ...
*> Oracle Event Received!
DBMS_ALERT.SIGNAL name = STACKOVERFLOW
Message= Hello StackOverflow! 21:55:44
*> Oracle Event TIMEOUT!
Sending a DBMS_ALERT Signal to StackOverflow ...
*> Oracle Event Received!
DBMS_ALERT.SIGNAL name = STACKOVERFLOW
Message= Hello StackOverflow! 21:55:45
DB OracleSession2 Disconnected!
*> Oracle Event TIMEOUT!
Stopping OracleEvent handler.
* This is where the Hangup problem gets called!
*> Oracle Event STOP!
OracleEvent Handler Stopped OK!
* If we got here, either there were no events...
or the Bug is Fixed B-)
DB OracleSession1 Disconnected!
==========================
答案 0 :(得分：0)
以下是DOA 4.1.1源代码中TOracleEvent.Stop例程的修订版。此例程中未更改的批量DOA代码将替换为＆＃39;。 。 。＆＃39;
此修订过程是（迄今为止）TOracleEvent.Stop（）调用的功能性工作，间歇性地导致我的应用程序挂起。
procedure TOracleEvent.Stop;
var
bLoggedOff: boolean;
begin
. . .
. . .
// Skip the CriticalSection Enter/Leave toggle.
// This is causing my application to get stuck here!
//CriticalSection.Enter;
//CriticalSection.Leave;
. . .
. . .
// LogOff the duplicate sessions
if (not KeepConnection) then begin
bLoggedOff := false;
// Keep trying the logoff until we actually get Logged Off or disconnected.
while (not bLoggedOff) do begin
try
if ((InternalSession <> nil) and (InternalSession.Connected)) then begin
InternalSession.LogOff;
end;
if ((StopSession <> nil) and (StopSession.Connected)) then begin
StopSession.LogOff;
end;
bLoggedOff := true;
except
on exLogoff: Exception do begin
// This error is typically ORA-24909: Call In Progress, Current Operation Cancelled.
// Sink this hangover error by sleeping it off
Sleep(1000);
end;
end;
end;
end;
end;