发表于：
2009-11-10 20:49:44
大家晚上好：
我现在看李维写的《Delphi 5.x 分布式多层应用系统篇》，在运行5-1节示例代码的时候。
客户端的代码运行到红色字体的时候就会出错，错误代码是：“CDSBash Cannot perform this operation on a closed dataset”！请大家帮忙看一下，为什么会出这样的错？CDSBash 的属性FetchOnDemand 已设为False. PacketRecords 设为10。
关于Delphi 三层无状态分段取数据。如果大家有什么好的想法或建议，可以告诉小弟！
在此先感谢一下各位了。
客户端代码如下:
unit main;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, DB, DBClient, MConnect, Grids, Wwdbigrd, Wwdbgrid, StdCtrls,
Buttons, Mask, DBCtrls, SConnect, ExtCtrls;
type
TForm1 = class(TForm)
DataSource1: TDataSource;
wwDBGrid1: TwwDBGrid;
Label1: TLabel;
Edit1: TEdit;
SpeedButton1: TSpeedButton;
SpeedButton2: TSpeedButton;
DBNavigator1: TDBNavigator;
SpeedButton3: TSpeedButton;
CDSBash: TClientDataSet;
SocketConnection1: TSocketConnection;
CDSBashsh01: TStringField;
CDSBashsh02: TStringField;
CDSBashsh03: TStringField;
CDSBashsh04: TStringField;
CDSBashsh05: TStringField;
CDSBashsh06: TStringField;
CDSBashsh07: TStringField;
CDSBashsh08: TBCDField;
CDSBashsh09: TStringField;
CDSBashsh10: TBCDField;
CDSBashsh11: TBCDField;
CDSBashsh12: TBCDField;
CDSBashsh13: TBCDField;
CDSBashsh14: TStringField;
CDSBashsh15: TStringField;
CDSBashsh16: TBCDField;
CDSBashsh17: TBCDField;
procedure FormDeactivate(Sender: TObject);
procedure SpeedButton1Click(Sender: TObject);
procedure CDSBashBeforeGetRecords(Sender: TObject;
var OwnerData: OleVariant);
procedure SpeedButton2Click(Sender: TObject);
procedure CDSBashReconcileError(DataSet: TCustomClientDataSet;
E: EReconcileError; UpdateKind: TUpdateKind;
var Action: TReconcileAction);
procedure FormActivate(Sender: TObject);
procedure CDSBashAfterGetRecords(Sender: TObject;
var OwnerData: OleVariant);
procedure SpeedButton3Click(Sender: TObject);
private
{ Private declarations }
vOwnerData :OleVariant;
v2OwnerData :OleVariant;
bTrueEOF :Boolean;
public
{ Public declarations }
function GetKeyFieldValue(Sender:Tobject):OleVariant;
end;
var
Form1: TForm1;
implementation
uses Unit1;
{$R *.dfm}
procedure TForm1.FormDeactivate(Sender: TObject);
begin
SocketConnection1.Connected :=false;
CDSBash.Active :=false;
end;
procedure TForm1.SpeedButton1Click(Sender: TObject);
var
abk :TBookMark;
begin
try
if (not bTrueEOF) then
begin
try
abk :=CDSBash.GetBookmark;
if (CDSBash.GetNextPacket < CDSBash.PacketRecords ) then
bTrueEOF :=True;
CDSBash.Last;
vOwnerData :=CDSBash.fieldbyname('sh01').AsString;
CDSBash.GotoBookmark(aBK);
CDSBash.Next;
finally
CDSBash.FreeBookmark(aBK);
end;
end;
except
on Exception do;
end;
Edit1.Text :=IntToStr(CDSBash.RecordCount);
end;
procedure TForm1.CDSBashBeforeGetRecords(Sender: TObject;
var OwnerData: OleVariant);
begin
if ((VarIsEmpty(vOwnerData)) or (VarIsNull(vOwnerData))) then
vOwnerData :=GetKeyFieldValue(Sender);
OwnerData :=vOwnerData;
end;
procedure TForm1.SpeedButton2Click(Sender: TObject);
begin
CDSBash.ApplyUpdates(0);
end;
procedure TForm1.CDSBashReconcileError(DataSet: TCustomClientDataSet;
E: EReconcileError; UpdateKind: TUpdateKind;
var Action: TReconcileAction);
begin
//HandleReconcileError(CDSBash, UpdateKind, E);
if E.ErrorCode <>0 then
begin
messagedlg('更新失败'+#13#10+E.Message,mtInformation,[mbOk],0);
end;
end;
procedure TForm1.FormActivate(Sender: TObject);
begin
SocketConnection1.Connected :=true;
CDSBash.Active :=true;
Edit1.Text :=IntToStr(CDSBash.RecordCount);
end;
procedure TForm1.CDSBashAfterGetRecords(Sender: TObject;
var OwnerData: OleVariant);
//var
// CurRecord:TBookMark;
// AA:STRING;
begin
{ try
with Sender as TClientDataSet do
begin
CurRecord :=GetBookmark;
try
last;
AA := CDSBash.FieldByName('sh01').value;
vOwnerData :=CDSBash.FieldByName('sh01').value;
GotoBookmark(CurRecord);
finally
FreeBookMark(CurRecord);
end;
end;
except
on Exception do;
end; }
end;
procedure TForm1.SpeedButton3Click(Sender: TObject);
begin
CDSBash.Refresh;
end;
function TForm1.GetKeyFieldValue(Sender: Tobject): OleVariant;
var
CurRecord: TBookMark;
begin
try
with Sender as TClientDataSet do
begin
CurRecord :=GetBookmark;
try
last;
Result :=FieldbyName('sh01').Value;
GotoBookMark(CurRecord);
finally
FreeBookMark(CurRecord);
end;
end;
except
on Exception do;
end;
end;
end.
**************************************
服务器端的代码是如下：
unit RemoteData;
{$WARN SYMBOL_PLATFORM OFF}
interface
uses
Windows, Messages, SysUtils, Classes, ComServ, ComObj, VCLCom, DataBkr,
DBClient, pBash_TLB, StdVcl, DB, ADODB, Provider;
type
Ttestbash = class(TRemoteDataModule, Itestbash)
ADObash: TADOQuery;
DSPBash: TDataSetProvider;
ADOConnection1: TADOConnection;
ADObashsh01: TStringField;
ADObashsh02: TStringField;
ADObashsh03: TStringField;
ADObashsh04: TStringField;
ADObashsh05: TStringField;
ADObashsh06: TStringField;
ADObashsh07: TStringField;
ADObashsh08: TBCDField;
ADObashsh09: TStringField;
ADObashsh10: TBCDField;
ADObashsh11: TBCDField;
ADObashsh12: TBCDField;
ADObashsh13: TBCDField;
ADObashsh14: TStringField;
ADObashsh15: TStringField;
ADObashsh16: TBCDField;
ADObashsh17: TBCDField;
procedure DSPBashBeforeGetRecords(Sender: TObject;
var OwnerData: OleVariant);
procedure RemoteDataModuleCreate(Sender: TObject);
procedure RemoteDataModuleDestroy(Sender: TObject);
private
{ Private declarations }
protected
class procedure UpdateRegistry(Register: Boolean; const ClassID, ProgID: string); override;
public
{ Public declarations }
end;
implementation
{$R *.DFM}
class procedure Ttestbash.UpdateRegistry(Register: Boolean; const ClassID, ProgID: string);
begin
if Register then
begin
inherited UpdateRegistry(Register, ClassID, ProgID);
EnableSocketTransport(ClassID);
EnableWebTransport(ClassID);
end else
begin
DisableSocketTransport(ClassID);
DisableWebTransport(ClassID);
inherited UpdateRegistry(Register, ClassID, ProgID);
end;
end;
procedure Ttestbash.DSPBashBeforeGetRecords(Sender: TObject;
var OwnerData: OleVariant);
begin
with Sender as TDataSetProvider do
begin
DataSet.Open;
DataSet.Locate('sh01',OwnerData,[]);
DataSet.Next;
end;
end;
procedure Ttestbash.RemoteDataModuleCreate(Sender: TObject);
begin
ADOConnection1.Connected := True;
ADOBash.Active := True;
end;
procedure Ttestbash.RemoteDataModuleDestroy(Sender: TObject);
begin
ADOConnection1.Connected := false;
ADOBash.Active := false;
end;
initialization
TComponentFactory.Create(ComServer, Ttestbash,
Class_testbash, ciMultiInstance, tmApartment);
end. |
