Delphi采用接口实现DLL调用

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Delphi采用接口实现DLL调用

2024-09-09 11:04:55 214人阅读

Delphi使用模块化开发，可以采用DLL或者BPL，两者的区别是BPL只能被同版本的Delphi使用，DLL可以被不同版本和不同开发工具的开发的软件调用。

因此我们的软件大多使用Delphi作为界面以及部分DLL模块的开发工具。

DLL模块之间通过接口方式调用。

1.对象创建采用工厂模式，每个DLL负责某个对象或若干个对象的创建及释放，例如：

DLL工程为http客户端(prjHttp.DLL)模块，通过DLL导出的GetHttpClientFactory获取http客户端工厂接口，通过接口创建Http客户端和释放Http客户端，工程

包括3个文件：工程文件，实现单元，接口单元。

调用此DLL的程序仅需要包含接口单元。

DLL工程文件

library prjHttp;uses   System.SysUtils,   System.Classes,   utHTTPClient in ‘utHTTPClient.pas‘;{$R *.res}exports     GetHttpClientFactory;end.

utHttpClient示例

unit utHttpClient;interfaceuses utBaseObject, utHttpInterface, Classes, SysUtils;type  .........  THTTPClientConnection = class(TIntObject, IHTTPClientConnection)  public    function Connect: Boolean;    function Info: IHTTPClientConnectionInfo;    function TcpConnection: ITcpConnection;    function DataConnection: IConnection;    function Param:IHttpClientConnectionParam;  public    constructor Create;    destructor Destroy; override;  end;  THttpClientConnectionFactory = class(TIntObject, IHttpClientConnectionFactory)  protected    FObjectPool: THTTPClientConnectionPool;  public    constructor Create;    destructor Destroy; override;    procedure CreateHttpClient(out Conn: IHTTPClientConnection);    procedure DestroyHttpClient(var aClient);  end;function GetHttpClientFactory: IHttpClientConnectionFactory;implementation............var  HttpClients: THttpClientConnectionFactory;function GetHttpClientFactory: IHttpClientConnectionFactory;begin  if not Assigned(HttpClients) then    HttpClients := THttpClientConnectionFactory.Create;  Result        := HttpClients;end;initializationfinalization  if Assigned(HttpClients) then FreeAndNil(HttpClients);end.

utHttpInterface接口文件示例

unit utHttpInterface;interfaceuses utBaseInterface;const  IID_IHTTPClientConnectionInfo            = ‘{24C3D6BF-EC3D-4783-AD98-A5C6E4F24F19}‘;  IID_IHTTPClientConnectionParam           = ‘{0FA49A71-48BF-40CD-9D77-63B233C4F717}‘;  IID_IHTTPClientConnection                = ‘{78C39E26-A690-4022-9E97-6035768CE75C}‘;  IID_IHTTPClientConnectionEvent           = ‘{2FB0AC19-9994-4E77-B105-121192943EBC}‘;  IID_IHttpClientConnectionFactory         = ‘{429C5C2B-C1E3-4871-9631-E3B943619EFD}‘;  GUID_IHTTPClientConnectionInfo: TGUID    = IID_IHTTPClientConnectionInfo;  GUID_IHTTPClientConnectionParam: TGUID   = IID_IHTTPClientConnectionParam;  GUID_IHTTPClientConnection: TGUID        = IID_IHTTPClientConnection;  GUID_IHTTPClientConnectionEvent: TGUID   = IID_IHTTPClientConnectionEvent;  GUID_IHttpClientConnectionFactory        = IID_IHttpClientConnectionFactory;type  IHttpClientConnectionParam = interface    [‘{0FA49A71-48BF-40CD-9D77-63B233C4F717}‘]    function TcpParam: ITcpConnectionParam;    function GetMethod: PAnsiChar;    function GetPathAndParams: PAnsiChar;    function GetAgent: PAnsiChar;    function GetHeader: PAnsiChar;    function GetData: PAnsiChar;    function GetUserName: PAnsiChar;    function GetPassword: PAnsiChar;    procedure SetValue(const ServerAddr: PAnsiChar; const ServerPort: Integer; const UserName, Password, Method, PathAndParams, Agent, Header, Data: PAnsiChar);  end;  IHTTPClientConnectionInfo = interface(ITcpConnectionInfo)    [‘{24C3D6BF-EC3D-4783-AD98-A5C6E4F24F19}‘]    function Auth: PAnsiChar;  end;  IHTTPClientConnection = interface;  IHTTPClientConnectionEvent=interface    [‘{2FB0AC19-9994-4E77-B105-121192943EBC}‘]    procedure OnHeader(const Http:IHTTPClientConnection; const Header:Pointer; const HeaderLenght:NativeInt);    procedure OnStartReceiveContent(const Http:IHTTPClientConnection; const ContentLength:NativeInt);    procedure OnReceiveProgress(const Http:IHTTPClientConnection; const ContentLenght, ContentReceived:NativeInt);    procedure one rror(const Http:IHTTPClientConnection; const ErrStr:PAnsiChar);  end;  THttpClientConnectionEvent = (heHeader, heStartReceiveContent, heReceiveProgress, heError);  IHTTPClientConnection = interface    [IID_IHTTPClientConnection]    function Connect: Boolean;    function Info: IHTTPClientConnectionInfo;    function TcpConnection: ITcpConnection;    function DataConnection: IConnection;    function Param:IHttpClientConnectionParam;  end;  IHttpClientConnectionFactory = interface    [IID_IHttpClientConnectionFactory]    procedure CreateHttpClient(out Conn: IHTTPClientConnection);    procedure DestroyHttpClient(var aClient);  end;implementationend.

调用prjHttp.DLL的Delphi工程可以包含下面的单元以及上面的接口单元utHttpInterface.pas即可

将utHttpDLL.pas中的 //{$define utHttpDLL) 去掉注释，即可以将http客户端这些代码包含到Delphi工程中。

unit utHttpDLL;//{$define utHttpDLL}interfaceuses utHttpInterface, utBaseInterface;var  HttpClientFactory: IHttpClientConnectionFactory;implementation{$ifdef utHttpDLL}uses Windows, SysUtils;const  DLLName = ‘prjHttp.DLL‘;type  Proc = function: IInterface;var  LibHandle: THandle;function GetHttpClientFactory: IHttpClientConnectionFactory;begin  Result := HttpClientFactory;end;procedure Init;var  P: Proc;begin  LibHandle := SafeLoadLibrary(DLLName);  if LibHandle <> INVALID_HANDLE_VALUE then  begin    P                  := GetProcAddress(LibHandle, ‘GetHttpClientFactory‘);    if Assigned(P) then      HttpClientFactory := IHttpClientConnectionFactory(P);  end  else    raise Exception.Create(‘无法打开库文件‘ + DLLName);  if not Assigned(HttpClientFactory) then    raise Exception.Create(DLLName + ‘找不到指定函数‘);end;procedure Done;begin  if LibHandle <> INVALID_HANDLE_VALUE then    FreeLibrary(LibHandle);  Pointer(HttpClientFactory)  := nil;end;{$else}uses utHttpClient;procedure Init;begin  HttpClientFactory:= GetHttpClientFactory;end;procedure Done;begin  Pointer(HttpClientFactory):=nil;end;{$endif}initializationInit;finalizationDone;end.

2.DLL中输出接口对象的生命周期管理

Delphi对接口采用引用计数的方法管理对象生命周期，但是DLL中输出的对象可能不是被Delphi调用，其引用计数不一定正确，因此DLL中接口对象的生命周期不由Delphi编译器自动生成的代码管理，而是程序员自己控制，所以上面

的工厂包括构造和解析两个接口对象的生命周期管理方法。

所有接口对象应该集成自下面的接口，而不应该继承自Delphi自带的TInterfacedObject：

  TIntObject = class(TObject, IInterface)  protected    function QueryInterface(const IID: TGUID; out Obj): HResult; stdcall;    function _AddRef: Integer; stdcall;    function _Release: Integer; stdcall;  end;function TIntObject.QueryInterface(const IID: TGUID; out Obj): HResult;begin  if GetInterface(IID, Obj) then    Result := 0  else    Result := E_NOINTERFACE;end;function TIntObject._AddRef: Integer;begin  Result := -1;end;function TIntObject._Release: Integer;begin  Result := -1end;

3.自管理接口对象在Delphi调用注意事项

1）接口赋值

　　错误代码：（Delphi编译器产生代码会先判断接口指针是否为nil，如果非nil自动调用接口的_Release方法）

  var P1:IHttpServer。。。。。。。。。。。。　　  P1:=FServer.Param; 　　 P1.SetValue(PWideChar(aName), PAnsiChar(AnsiString(ServerAddr)), ServerPort, 10000, 10,0, 40000);

　　建议代码：

  var P1:IHttpServer................  Pointer(P1):=nil;　　    P1:=FServer.Param;  //如果赋值前P1不是nil,程序会线调用P1._Release后再赋值

2）局部接口变量
　　错误代码：

constructor TTcpServerSplitter.Create(aName:String; ServerAddr: String; ServerPort: Integer;  RemoteAddr: String; RemotePort: Integer);var  Service:IInterfaceObservable;  P1:ITcpConnectionServerParam;  P2:ITcpConnectionParam;begin  inherited Create;  FServerEvent:=TTcpConnectionServerEventAdapter.Create(Self as ITcpConnectionServerEvent);  FTcpConnectionEvent:=TTcpConnectionEventAdapter.Create(Self as ITcpConnectionEvent);  FConnectionEvent:=TConnectionEventAdapter.Create(Self as IConnectionEvent);  TcpServerFactory.CreateTcpConnectionServer(FServer);  P1:=FServer.Param;  P1.SetValue(PWideChar(aName), PAnsiChar(AnsiString(ServerAddr)), ServerPort, 10000, 10,0, 40000);  RegistObserver(FServer, FServerEvent);  TcpClientFactory.CreateTcpConnection(FRemote);  P2:=FRemote.Param;  P2.SetValue(PAnsiChar(AnsiString(RemoteAddr)), RemotePort, Self);  RegistObserver(FRemote,FTcpConnectionEvent);end;

上面代码中运行退出后，Delphi编译器会在此代码后面自动调用P1._Release; P2._Release,
　　建议代码：

constructor TTcpServerSplitter.Create(aName:String; ServerAddr: String; ServerPort: Integer;  RemoteAddr: String; RemotePort: Integer);var  Service:IInterfaceObservable;  P1:ITcpConnectionServerParam;  P2:ITcpConnectionParam;begin  inherited Create;  FServerEvent:=TTcpConnectionServerEventAdapter.Create(Self as ITcpConnectionServerEvent);  FTcpConnectionEvent:=TTcpConnectionEventAdapter.Create(Self as ITcpConnectionEvent);  FConnectionEvent:=TConnectionEventAdapter.Create(Self as IConnectionEvent);  TcpServerFactory.CreateTcpConnectionServer(FServer);  P1:=FServer.Param;  P1.SetValue(PWideChar(aName), PAnsiChar(AnsiString(ServerAddr)), ServerPort, 10000, 10,0, 40000);  RegistObserver(FServer, FServerEvent);  TcpClientFactory.CreateTcpConnection(FRemote);  P2:=FRemote.Param;  P2.SetValue(PAnsiChar(AnsiString(RemoteAddr)), RemotePort, Self);  RegistObserver(FRemote,FTcpConnectionEvent);  Pointer(P1):=nil;  Pointer(P2):=nil;end;

3)函数返回值为接口指针

如下面的示例中FServer.Param定义为function THttpServer.Param:IHttpServerParam，返回的是接口类型，下面的代码直接调用Param.SetValue方法：

constructor TTcpServerSplitter.Create(aName:String; ServerAddr: String; ServerPort: Integer;  RemoteAddr: String; RemotePort: Integer);var  Service:IInterfaceObservable;  P1:ITcpConnectionServerParam;  P2:ITcpConnectionParam;begin  inherited Create;  FServerEvent:=TTcpConnectionServerEventAdapter.Create(Self as ITcpConnectionServerEvent);  FTcpConnectionEvent:=TTcpConnectionEventAdapter.Create(Self as ITcpConnectionEvent);  FConnectionEvent:=TConnectionEventAdapter.Create(Self as IConnectionEvent);  TcpServerFactory.CreateTcpConnectionServer(FServer);  FServer.Param.SetValue(PWideChar(aName), PAnsiChar(AnsiString(ServerAddr)), ServerPort, 10000, 10,0, 40000);  RegistObserver(FServer, FServerEvent);  TcpClientFactory.CreateTcpConnection(FRemote);  FRemote.Param.SetValue(PAnsiChar(AnsiString(RemoteAddr)), RemotePort, Self);  RegistObserver(FRemote,FTcpConnectionEvent);end;

上面的代码，Delphi编译器会自动生成两个接口变量，保存FServer.Param和FRemote.Param，由于FServer和FRemote为TTcpServerSplitter对象的全局变量，所以接口在TTcpServerSplitter对象释放时，被调用_Release

将导致内存访问异常。

constructor TTcpServerSplitter.Create(aName:String; ServerAddr: String; ServerPort: Integer;  RemoteAddr: String; RemotePort: Integer);var  Service:IInterfaceObservable;  P1:ITcpConnectionServerParam;  P2:ITcpConnectionParam;begin  inherited Create;  FServerEvent:=TTcpConnectionServerEventAdapter.Create(Self as ITcpConnectionServerEvent);  FTcpConnectionEvent:=TTcpConnectionEventAdapter.Create(Self as ITcpConnectionEvent);  FConnectionEvent:=TConnectionEventAdapter.Create(Self as IConnectionEvent);  TcpServerFactory.CreateTcpConnectionServer(FServer);  P1:=FServer.Param;  P1.SetValue(PWideChar(aName), PAnsiChar(AnsiString(ServerAddr)), ServerPort, 10000, 10,0, 40000);  RegistObserver(FServer, FServerEvent);  TcpClientFactory.CreateTcpConnection(FRemote);  P2:=FRemote.Param;  P2.SetValue(PAnsiChar(AnsiString(RemoteAddr)), RemotePort, Self);  RegistObserver(FRemote,FTcpConnectionEvent);  Pointer(P1):=nil;     Pointer(P2):=nil;end;

4）对象中的接口变量，在对象释放时，需要将接口变量清空。

destructor TTcpServerSplitter.Destroy;begin  Stop;  Pointer(FServer):=nil;  Pointer(FRemote):=nil;  inherited;end;

Delphi采用接口实现DLL调用

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