关于VisiBroker For Delphi的使用

《关于VisiBroker For Delphi的使用》(3)-CORBA技术实践（一）email: 3boy@3,数组对象与简单数据对象的传递前面提到了一些较为简单的数据操作，我们都可以想象一下，如果操作COR BA对象与操作C/S结构的数据对象一样的方便，那么CORBA又有什么神奇了，不知道看过李维的分布式多层应用系统的书籍时，是否留意到李维对CORBA 的评价，无论你看过还是没有看过，我都要告诉正在使用CORBA编程的朋友们，CORBA比COM/CO M+简单，而CORBA的跨平台特性，以及与COM/COM+同样的负载平衡能力，足以让我们将这项分布式技术应用到应用体系的设计之中，其实对于使用Bor land的产品开发分布式系统无论你采用CORBA或是COM/COM+其实最核心的技术就是MIDAS，因为你总可以在CORBA/COM/COM+中看到MIDAS的影子，所以我建议无论你是准备学习CORBA还是学习COM/COM+最好先学习一下MIDAS,本文不涉及MIDAS，关于MIDAS请看李维的《Delphi5.X分布式多层应用—系统篇》。

为什么我从开始就一直要大家使用文本编辑器之类的东西书写IDL，而不用TypeLibrary来书写IDL,其实我觉得只是为了让刚刚接触CORBA的程序员获得一些更多的IDL方面的知识罢了，在实际的开发中你可以完全很方便的使用TypeLib rary来编写接口规则。

下面我简要的列举几类IDL书写的事例与利用IDL2PAS生成的PASCAL代码。

1、）常量的定义/**IDL书写**/module MyCRB{const long iMyConst=1;interface myFace {const long iiMyConst=2;};};/**Pascal**/unit MyCRB_I;interfaceuses Corba;constiMyCOnst:integer=1;myFace_iiMyConst=2;2、)不在接口中申明的常量/**IDL**/module MyCRB{const long myconst=1;};/*pascal*/unit MyCRB_I;interfaceconst myconst:integer=1; 3、)枚举类型/*IDL*/enum MyCRBKind{A,B,C,D,……..} /*pascal*/myCRBkind=(A,B,C,D……..); 4、）结构体/*IDL*/struct mystructtype{long X;string Y;boolean Z;};/*pascal*///XXX_I.pastype mystructtype=interface;//XXX_C.pasmystructtype=interfacefunction _get_X:integer;function _get_Y:string;function _get_Z:boolean;procedure _set_X(const Value:integer);procedure _set_Y(const Value:string);procedure _set_Z(const Value:boolean);property X:integer read _get_X write _Set_X;property Y:string read _get_Y write _Set_Y;property Z:boolean read _get_Z write _Set_Z;…….还有太多的代码，自己创建一个看一下，为了节约篇幅我就不做详细的翻译了下面请大家试一下以下的申明会生成什么样的Pascal代码5、）联合体union un_exp switch(long){case 1:long x;case 2:string y;case 3:st_exp Z;};6、sequence(我理解为动态数组)typedef sequence <long> UnboundeSeq;typedef sequence <long,42> ShortBoundSeq7, 数组const long ArrayBound=10;typedef long longArray[ArrayBound];8, 抽象接口module exp{interface myface{long op(in string s);};};9,多重继承module M{ interface A{void A1();void A2(); };interface B{void B1();void B2();};interface AB:B,A{ void AB1()void AB2();};};10,交叉模型定义module m1{ interface if1;module m2{interface if2{m1::if1 getIf1();};interface if1{m2::if2 getif2()};};};以上我介绍了一些数据的定义规范,然而我们需要不仅仅是这样的一些比较抽象的接口定义法则,我们要将法则应用到实际的开发中去,那么我们又是如何运用这些法则了,对于接口描述语言的翻译我前面讲到直接使用IDL2PAS就不讲了,以后的章节中也不会在去将如何转换的问题。

下面我们实践一下：编写接口定义一个返回为浮点类型，输入为短整型变量数组对象的方法typedef short ArrayType[3];//自定义类型定义长度为3的数组interface Account {float InputArray(in ArrayType myArray);//输入为整形数组，返回类型为float的方法};//服务端程序的处理xxx_impl.pasinterfaceusesSysUtils,CORBA,account_i,account_c;typeTAccount = class;TAccount = class(TInterfacedObject, account_i.Account) protected//******************publicconstructor Create;function InputArray ( const myArray : account_i.ArrayType): Sing le;end;implementationuses ServerMain;constructor TAccount.Create;begininherited;end;function TAccount. InputArray (const myArray : account_i.ArrayType): Single;varj: Integer;begin// account_i.ArrayType是指我们自定义的数组类型在account_I单元中for j := 0 to 2 dobeginForm1.Memo1.Lines.Add('myArray[' + IntToStr(j) + '] = ' + IntToSt r(myArray[j]) );//接受从客户端传递过来的数组变量并将其依次加入到主窗体的MEMO中 end;result := random * 100;//返回一个随机数end;initializationrandomize;end.//服务端程序主单元unit ServerMain;interfaceusesWindows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Di alogs, Corba,Account_I, Account_C, Account_S, Account_Impl, StdCtrls;typeTForm1 = class(TForm)Memo1: TMemo;procedure FormCreate(Sender: TObject);private{ private declarations }protected{ protected declarations }Acct : Account; // skeleton 对象procedure InitCorba;public{ public declarations }end;varForm1: TForm1;implementation{$R *.dfm}procedure TForm1.InitCorba;beginCorbaInitialize;// Add CORBA server Code HereAcct := TAccountSkeleton.Create('Array Server', TAccount.Create); BOA.ObjIsReady(Acct as _Object);end;procedure TForm1.FormCreate(Sender: TObject);beginInitCorba;Memo1.Lines.Add('Account object created...');Memo1.Lines.Add('Server is ready');end;end.//客户端程序unit ClientMain;interfaceusesWindows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Di alogs,Corba, StdCtrls, Account_I, Account_C;typeTForm1 = class(TForm)Button1: TButton;Label1: TLabel;procedure FormCreate(Sender: TObject); procedure Button1Click(Sender: TObject); private{ private declarations }protected{ protected declarations }Acct : Account;myArray : ArrayType;procedure InitCorba;public{ public declarations }end;varForm1: TForm1;implementation{$R *.dfm}procedure TForm1.InitCorba;beginCorbaInitialize;Acct := TAccountHelper.bind;end;procedure TForm1.FormCreate(Sender: TObject); varj: Integer;beginInitCorba;for j := 0 to 2 domyArray[j] := (j + 1) * 100;end;procedure TForm1.Button1Click(Sender: TObject); beginLabel1.Caption := FormatFloat('InputArray = $#,##0.00', Acct.inputA rray(myArray));end;end.上面的程序实例很简单我就不一一说明了，下面我们来看一个数据访问的实例//IDLinterface Employee {any getEmployeesByName(in string name);};接口方法声明单元//XXX_Impl.pasinterfaceusesSysUtils,CORBA,employee_i,employee_c;typeTEmployee = class;TEmployee = class(TInterfacedObject, employee_i.Employee)publicconstructor Create;function getEmployeesByName ( const name : AnsiString): ANY; end;implementationuses dmEmployee,DMPooler, provider,DSIntf,ServerMain;constructor TEmployee.Create;begininherited;end;function TEmployee.getEmployeesByName ( const name : AnsiString): AN Y;varDM: TdmEmploy;RecsOut: Integer;Options: TGetRecordOptions;beginOptions := [grMetaData,grReset]; //must specify meta dataDM := ModulePooler.GetModule as TdmEmploy; //Get instance of datamo dule from PooltryDM.qryEmployee.Close;DM.qryEmployee.ParamByName('name').AsString:= name + '%';//显示连接服务器的数量Inc(Form1.HitCount);bel1.Caption := Format('Hit Count = %d', [Form1.HitCoun t]);DM.qryEmployee.Open;Result:=DM.proEmployee.GetRecords(-1, RecsOut, Byte(Options)); DM.qryEmployee.Close;finallyModulePooler.FreeModule(DM);//Return instance of DataModule to po olend;end;initialization//将TdmEmploy对象放入共享池中ModulePooler.ModuleClass := TdmEmploy;end.//共享池的声明单元主要描述如何提供一个多客户的访问数据提供unit DMPooler;interfaceuses SysUtils, Classes, Forms, SyncObjs, Windows;type//本单元用于为每个客户提供一个独立使用的DataModule对象，相当于我们在以前的CORBA DataModule中选择创建的多线程对象一样的功能TDataModuleClass = class of TDataModule; //定义类TPooledModule = record//声明记录类型Module: TDataModule; //继承标准的TdataModuleInUse: Boolean; //标明上面继承的TdataModule是否在使用end;TModulePooler = classprivateFCSect: TCriticalSection; //允许线程自己改变FModulesFModuleClass: TDataModuleClass; //在共享池中类化TDataModule FModules: array of TPooledModule; //定义一个动态的对象记录数组FSemaphore: THandle; //限定同时使用的用户规则publicproperty ModuleClass: TDataModuleClass read FModuleClass write FM oduleClass;constructor Create;destructor Destroy; override;function GetModule: TDataModule;procedure FreeModule(DataModule: TDataModule);end;constPoolSize = 5;varModulePooler: TModulePooler = nil;implementationuses Dialogs;{ TModulePool }constructor TModulePooler.Create;beginIsMultiThread := True;FCSect := TCriticalSection.Create;FSemaphore := CreateSemaphore(nil, PoolSize, PoolSize, nil); end;destructor TModulePooler.Destroy;beginFCSect.Free;CloseHandle(FSemaphore);end;procedure TModulePooler.FreeModule(DataModule: TDataModule); varI: Integer;beginFCSect.Enter;tryfor I := 0 to Length(FModules) - 1 doif FModules[I].Module = DataModule thenFModules[I].InUse := False;ReleaseSemaphore(FSemaphore, 1, nil);finallyFCSect.Leave;end;end;function TModulePooler.GetModule: TDataModule;varI: Integer;beginResult := nil;if WaitForSingleObject(FSemaphore, 5000) = WAIT_TIMEOUT then raise Exception.Create('Server too busy');FCSect.Enter;tryif Length(FModules) = 0 thenbeginSetLength(FModules, PoolSize);for I := 0 to PoolSize - 1 dobeginFModules[I].InUse := False;FModules[I].Module := FModuleClass.Create(Application); end;end;for I := 0 to Length(FModules) - 1 doif not FModules[I].InUse thenbeginFModules[I].InUse := True;Result := FModules[I].Module;Break;end;finallyFCSect.Leave;end;//检查曾经是否连接if not Assigned(Result) thenraise Exception.Create('Pool is out of capacity');end;initializationModulePooler := TModulePooler.Create;finalizationModulePooler.Free;end.//本单元是一个通用的方法单元，当然您也可以采用其他的方法来完成这样的一个功能//DataModule单元unit dmEmployee;interfaceusesWindows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Di alogs,Db, DBTables, Provider;typeTdmEmploy = class(TDataModule)Session1: TSession;EmployeeDatabase: TDatabase;qryEmployee: TQuery;proEmployee: TDataSetProvider;private{ Private declarations }public{ Public declarations }end;vardmEmploy: TdmEmploy;implementation{$R *.DFM}end.//服务器的主单元unit ServerMain;interfaceusesWindows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Di alogs,Grids, DBGrids, Db, DBTables, StdCtrls, Corba, Employee_I, Employee _C,Employee_S, Employee_Impl；typeTForm1 = class(TForm)Label1: TLabel;procedure FormCreate(Sender: TObject); private{ Private declarations }procedure CorbaInit;public{ Public declarations }hitcount : integer;end;varForm1: TForm1;myDBServer : Employee;implementation{$R *.DFM}procedure TForm1.CorbaInit;beginCorbaInitialize;myDBServer := TEmployeeSkeleton.Create('myServer', TEmployee.Creat e);Boa.ObjIsReady( myDBServer as _Object );end;procedure TForm1.FormCreate(Sender: TObject);beginCorbaInit;end;end.//客户端程序interfaceusesWindows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Di alogs,StdCtrls, Grids, Corba, Employee_i, Employee_c, Db, DBClient, ExtCt rls,DBCtrls, DBGrids;typeTForm1 = class(TForm)Button1: TButton;DBGrid1: TDBGrid;cdsEmployee: TClientDataSet;DataSource1: TDataSource;edtEmployeeName: TEdit;Memo1: TMemo;Label1: TLabel;procedure FormCreate(Sender: TObject);procedure Button1Click(Sender: TObject);private{ Private declarations }myEmployee : Employee;public{ Public declarations }end;varForm1: TForm1;implementation{$R *.DFM}procedure TForm1.FormCreate(Sender: TObject); beginmyEmployee := TEmployeeHelper.bind;end;procedure TForm1.Button1Click(Sender: TObject); begincdsEmployee.Data := myEmployee.getEmployeesByName(edtEmployeeName.T ext);cdsEmployee.Open;end;end.我想大家应该可以看得懂上面的程序，如果看不懂也不要紧，下一次我将围绕这个实例展开一系列的问题描述并会同时于COM+/MIDAS进行比较说明，为了让大家留下一个思维的空间我在这里就不多说了。