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TDatabase components use the 'Defaut' session by
default. You simply need create a new session for each TDatabase you
create. To create a applicatoin only runtime Session we use the following
code...
constructor TProcessing.Create(Sender :
TClient);
// Each client has their own Processing
thread
begin
inherited create(True); // don't
execute immediately
Owner := Sender;
FreeOnTerminate := True;
ClientSession :=
TSession.Create(MainForm);
EnterCriticalSection(IncSessionNo);
try
Inc(MainForm.SessionNo);
ClientSession.SessionName := 'Client Session ' +
IntToStr(MainForm.SessionNo);
finally
LeaveCriticalSection(IncSessionNo);
end;
......
Note ClientSession is a TSession that all database
stuff is pointed to. The other bit ensures that the
clientSession.SessionName is unique. Hope this is of some use
Robert Martin
Software Engineer
Wild Software Ltd
----- Original Message -----
Sent: Monday, October 08, 2001 3:54
PM
Subject: Re: [DUG]: [Q] MIDAS (Socket
Connection), BDE, Threads
R,
Sorry. Part II. Is a TSession still necessary even
though the thread and the application have their own TDatabase components and
inherently their own Session?
At 15:50 08/10/2001 +1300, you wrote:
I have no
idea about how MIDAS works but you definately need to use a seperate session
with each thread when working with DBase etc. As to BDE crashes, me
too! Any app that crashes the BDE will crash any other app using the
BDE in my experiance.
Robert Martin
Software
Engineer
Wild Software Ltd
----- Original Message -----
From: Donovan J.
Edye
To: Multiple
recipients of list delphi
Sent: Monday, October 08, 2001
2:49 PM
Subject: [DUG]: [Q] MIDAS (Socket Connection), BDE,
Threads
G'Day All,
I have the following:
- A
component TCricketLiveScoringClient that uses a MIDAS socket connection to
make and handle a connection to a MIDAS server
- The above component
uses a TTXProcessThread to monitor changes in a local BDE table
- When
a change is detected by the it uses TCricketLiveScoringClient.ProcessTX()
to send the transaction to the MIDAS server
However what I am
finding is that if an exception is raised and the thread terminated and
the connection to the MIDAS server closed that the application dies
horribly with access violation(s), runtime error 216 etc. So my questions
are these:
- The thread uses its own TDatabase connection (and not
the TDatabase connection of the application that contains the component).
But does it require a TSession component as well? Are there issues here to
do with the BDE/Threading?
- It appears to me that the AppServer
property of the TSocketConnection "disappears" out from under me. However
no amount of:
if not
((VarIsNull(FSocketConnection.AppServer)) AND (varEmpty =
VarType(FSocketConnection.AppServer))
AND
(varNull =
VarType(FSocketConnection.AppServer))) then
seems to protect me from
getting the access violation.
Can anybody provide me with some
pointers etc.? Below find the necessary code, but if you need anything
else then please ask. I am at a loss as to how to solve this. Environment
is D5.01 Enterprise.
TIA
type
TNewTXDataEvent = procedure(ATXID : integer; ATXPayload : string; TotalTXs
: integer;
var EventCompleted : boolean;
var EventCompletedSuccessfully : boolean) of object;
TTXProcessThread = class(TThread)
private
FDatabase :
TDataBase;
FEventCompleted :
boolean;
FEventCompletedSuccessfully :
boolean;
FLastTxIDProcessed :
integer;
//FSession :
TSession;
FTXTable :
TTable;
FNewTXDataEvent :
TNewTXDataEvent;
protected
procedure Execute;
override;
procedure
FireCallBackEvent;
public
constructor
Create(CreateSuspended : Boolean; ADBPath :
string;
AStartTXID :
integer; ANewTXData : TNewTXDataEvent);
destructor Destroy; override;
end;
type
TCricketLiveScoringClient =
class(TCustomPanel)
private
FActive :
boolean;
FCricketAppGUID :
string;
FGlobalMatchCode :
string;
FLastTXProcessed :
integer;
FSocketConnection :
TSocketConnection;
FStatusPanel :
TPanel;
FTXPanel :
TPanel;
FMessages :
TStringList;
FTXProcessingThread :
TTXProcessThread;
FClientIP :
string;
FDBPath :
string;
FLoggedIn :
boolean;
FMidasServerPort :
SmallInt;
FMidasServerAddress :
string;
procedure AddMessage(AMsg :
string);
procedure
CustomOnDblClick(Sender : TObject);
function Get_Local_IPAddr : string;
procedure HandleExceptionError(AProcName, AErr, ADelphiError :
string);
function Login :
boolean;
function Logout :
boolean;
procedure NewDataEvent(ATXID :
integer; ATXPayload : string; TotalTXs :
integer;
var
EventCompleted : boolean; var EventCompletedSuccessfully :
boolean);
function
ProcessTX(AGlobalMatchCode : string; ATXID :
Integer;
const
ATXPayload : string; var ANextTXID :
Integer;
var
ASQLServerErrroCode : integer; var ASQLServerErrorDesc : string) :
WordBool;
procedure SetActive(const
Value : boolean);
procedure
SetGlobalMatchCode(const Value :
string);
procedure
SetMidasServerAddress(const Value :
string);
procedure
SetMidasServerPort(const Value : SmallInt);
protected
public
constructor Create(AOwner : TComponent);
override;
destructor Destroy;
override;
published
property Active : boolean read FActive write
SetActive;
property
Align;
property
BevelInner;
property
BevelOuter;
property CricketAppGUID :
string read FCricketAppGUID write
FCricketAppGUID;
property
GlobalMatchCode : string read FGlobalMatchCode write
SetGlobalMatchCode;
property DBPath :
string read FDBPath write FDBPath;
property MidasServerAddress : string read FMidasServerAddress write
SetMidasServerAddress;
property
MidasServerPort : SmallInt read FMidasServerPort write
SetMidasServerPort;
end;
function
TCricketLiveScoringClient.ProcessTX(AGlobalMatchCode : string; ATXID :
Integer;
const ATXPayload : string; var ANextTXID :
Integer;
var ASQLServerErrroCode : integer; var
ASQLServerErrorDesc : string) :
WordBool;
////////////////////////////////////////////////////////////////////////////////
//
PURPOSE: Processes the supplied TX information
const
PROC_NAME = 'TCricketLiveScoringClient.ProcessTX';
ERR_MSG
= 'I was unable to process the transaction.';
begin
//Show failure at this point
result :=
FALSE;
try
if not
((VarIsNull(FSocketConnection.AppServer)) AND (varEmpty =
VarType(FSocketConnection.AppServer))
AND
(varNull =
VarType(FSocketConnection.AppServer)))
then
begin
if
FSocketConnection.AppServer.ProcessTX(FClientIP, FCricketAppGUID,
AGlobalMatchCode,
ATXID,
ATXPayload, ANextTXID, ASQLServerErrroCode, ASQLServerErrorDesc) =
WordBool(TRUE) then
begin
result :=
TRUE;
FLastTXProcessed := ANextTXID -
1;
end;
end;
except
on E : Exception
do
HandleExceptionError(PROC_NAME, ERR_MSG, E.Message);
end;
end;
--
Donovan
----------------------------------------------------------------------
Donovan J. Edye [www.edye.wattle.id.au]
Namadgi Systems [www.namsys.com.au]
Voice: +61 2 6285-3460
Fax: +61 2 6285-3459
TVisualBasic =
Class(None);
Heard just before the 'Big Bang': "...Uh Oh...."
----------------------------------------------------------------------
GXExplorer [http://www.gxexplorer.org] Freeware Windows Explorer
replacement. Also includes freeware
delphi windows explorer components.
----------------------------------------------------------------------
--
Donovan
----------------------------------------------------------------------
Donovan J. Edye [www.edye.wattle.id.au]
Namadgi Systems [www.namsys.com.au]
Voice: +61 2 6285-3460
Fax: +61 2 6285-3459
TVisualBasic =
Class(None);
Heard just before the 'Big Bang': "...Uh Oh...."
----------------------------------------------------------------------
GXExplorer [http://www.gxexplorer.org] Freeware Windows Explorer
replacement. Also includes freeware
delphi windows explorer components.
----------------------------------------------------------------------
|
