clientfrm.pas

Delphi_7.0数据库开发源代码。有内容十一章节

unit clientfrm;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, DB, DBClient, MConnect, Grids, DBGrids, ObjBrkr;

type
  TForm1 = class(TForm)
    SimpleObjectBroker1: TSimpleObjectBroker;
    ClientDataSet1: TClientDataSet;
    DataSource1: TDataSource;
    DBGrid1: TDBGrid;
    DCOMConnection1: TDCOMConnection;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
try
    ClientDataSet1.ApplyUpdates(0);  //尝试数据更新
except
    //出现例外，更新不成功
on Exception do
begin
try
    //尝试关闭DCOMConnection1的连接，并关闭SimpleObjectBroker1到原来服务器的连接
    DCOMConnection1.Connected := False;    //尝试关闭原来的连接
    SimpleObjectBroker1.SetConnectStatus(DCOMConnection1.ComputerName, False);
finally
try
    DCOMConnection1.ComputerName := SimpleObjectBroker1.GetComputerForProgID
        (DCOMConnection1.ServerName); // 取得可用应用程序服务器的机器名称
    DCOMConnection1.Connected := True; //重新建立连接
    ClientDataSet1.ApplyUpdates(0);   //再次更新数据
except
    //连接失败或数据更新失败时，表示可能已经没有可有的连接，
        //则直接将数据写到一个指定的临时文件中
on EBrokerException do
    ClientDataSet1.SaveToFile('Sample.Dat'); // 保存数据
end;
end;
end;
end;

end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  ClientDataSet1.Open;   //打开数据库
end;

end.