delphi 三层小例子（入门）效果

直接上步骤效果，理论的我也不懂呢

一、服务器端：新建立 application 工程。之后建立数据单元文件New->other->Multitier->Remote Data Module（窗体命名 为Tserverdm）。

                     做数据链接。添加数据库控件：    adosql: TADOQuery;
    proversql: TDataSetProvider; 对外提供服务。
    consql: TADOConnection;  连接数据库

注意：设置TDataSetProvider 的allowcommandtext 为true. 非则不能 通过sql语句获取数据。

服务端代码如下：

unit udm;

{$WARN SYMBOL_PLATFORM OFF}

interface

uses
  Windows, Messages, SysUtils, Classes, ComServ, ComObj, VCLCom, DataBkr,
  DBClient, server_TLB, Forms,StdVcl, DB, ADODB,OleDB,ActiveX, Controls,Provider;

type
  Tserverdm = class(TRemoteDataModule, Iserverdm)
    adosql: TADOQuery;
    proversql: TDataSetProvider;
    consql: TADOConnection;
    procedure RemoteDataModuleCreate(Sender: TObject);
  private
    { Private declarations }
    Function ConnDB(UdlFileName:string):String;
      procedure Init_ConnectionString(FileName : String; Var Cons :string);
  protected
    class procedure UpdateRegistry(Register: Boolean; const ClassID, ProgID: string); override;
  public
    { Public declarations }
  end;
   var
       myserverdm :Tserverdm;
implementation

{$R *.DFM}

class procedure Tserverdm.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 Tserverdm.Init_ConnectionString(FileName: String;
  var Cons: string);
Var
  DataInit : IDataInitialize;
  FName    : POleStr;
  s        : POleStr;
  Tmp      : WideString;
begin      //直接读udl文件，从中获取数据链接字符串 ok!
  Tmp:= FileName;
  FName:=POleStr(Tmp);
  DataInit:=CreateComObject(CLSID_DataLinks)   as   IDataInitialize;
  DataInit.LoadStringFromStorage(FName,s);
  Cons:=s;
  DataInit:=nil;
end;



function Tserverdm.ConnDB(UdlFileName: string): String;
Var
    FileNames, SerName : String;
begin

   FileNames :=ExtractFilepath(Application.ExeName)+UdlFileName;
  Init_ConnectionString(FileNames,SerName);
  consql.Close;
  consql.ConnectionString:=SerName;
  Application.ProcessMessages;
  Try
    consql.Open;
    Result:='0';
  except
    On E:Exception Do
    Begin
      consql.Close;
      consql.Free;
      Result:='-1'+E.Message;
    End;
  end;
end;

procedure Tserverdm.RemoteDataModuleCreate(Sender: TObject);
begin
  ConnDB('dbsql.udl');
end;

initialization
  TComponentFactory.Create(ComServer, Tserverdm,
    Class_serverdm, ciMultiInstance, tmApartment);
end.

客户端建立：

 新建 applicatinon 工程。  添加组件： consql: TDCOMConnection; 连接服务端，设置属性：computerName 为本机名，servername 为添加服务端TDataSetProvider控件名称。
    cds1: TClientDataSet;   // TClientDataSet 属性servername 为添加服务端TDataSetProvider控件名称。
    ds2: TDataSource;
    dbgrd1: TDBGrid;  显示数据

客户端主要代码如下：

unit uMain;

interface

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

type
  TForm2 = class(TForm)
    consql: TDCOMConnection;
    cds1: TClientDataSet;
    btnser: TBitBtn;
    ds2: TDataSource;
    dbgrd1: TDBGrid;
    Button1: TButton;
    procedure btnserClick(Sender: TObject);
   
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.btnserClick(Sender: TObject);
begin
  with cds1 do
  begin
    Close;
    CommandText :='select top 10 bahao,xming,xbie, xxing from dbo.pub_bren ';
    Open;
  end;

end;

 

end.

 

procedure TForm2.Button1Click(Sender: TObject);
begin
cds1.Edit;
cds1.FieldByName('xxing').AsString :='a';
cds1.Post;
cds1.ApplyUpdates(0);
 //提交入数据库，看到生成的 修改语句是这样的   ，把四个字段都做为条件了，这样可不好啊。
//exec sp_executesql N'update dbo.pub_bren  set
// xxing = @P1
//where
// bahao = @P2 and
// xming = @P3 and
// xbie = @P4 and
// xxing is null
//',N'@P1 varchar(50),@P2 varchar(50),@P3 varchar(50),@P4 int','a','BR00000001','杨贵生',1
另外这样的 循环修改是不对的。
with not cds1.Eof do
begin
  edit;
  fieldbyname('').asstring :='a';
  post ;
end;

 

转载于:https://www.cnblogs.com/cnby/p/3990694.html