建立COM组件服务器

其他内容请浏览COM+分类

首先看下我们的目录结构：生成DLL的Project

这一节需要我们自己定义接口(发布接口)，利用MIDL 接口定义语言

COM服务器的三个关键要求：

接口：客户机通过接口与服务器进行通信；

组件类：提供所定义接口的实现方法；

类型库：编译的IDL文件向支持的COM环境传送接口信息。

首先在 vs中 建立IDL 文件：

代码如下：

import "oaidl.idl";
import "ocidl.idl";[ object,uuid(19900225-0700-0000-0000-000000000001)
]
interface IY : IUnknown {HRESULT Fy();
};[ object,uuid(19900225-0800-0000-0000-000000000001)
]
interface IZ : IUnknown {HRESULT Fz();
};[ uuid(19900225-0900-0000-0000-000000000001),version(1.0)
]
library CBLib {importlib("stdole32.tlb");[ uuid(19900225-0a00-0000-0000-000000000001)]coclass CB {[default] interface IY;[source] interface IZ;};
};

这里需要产生四个GUID，分别对应两个接口ID（IID），类型库ID（LIBID）和CoClassID（CLSID）。

右键点击该文件，选择编译，生成三个文件，

 将 除了划红线的文件， 剩下两个文件加入编译器中，创建Generated文件夹。

注： 若加入划红线的文件，将会产生 很多关于DLL的编译错误。

在自动生成的文件CB_i.c 中，我们可以看到系统已经帮我们生成了组件和接口的CSLID。

在CB_h.h 中可以看到，已经发布的接口和抽象方法

接下来我们需要实现组件的相关方法和类工厂：

组件类： 实现Fy，Fz，QueryInterface，AddRef，Release方法

class CB: public IY, public IZ{
public:// IUnknown implementationvirtual HRESULT __stdcall QueryInterface(const IID& iid, void** ppv);virtual ULONG __stdcall AddRef();virtual ULONG __stdcall Release();virtual HRESULT __stdcall Fy();virtual HRESULT __stdcall Fz();CB();~CB();
private:long m_cRef;
};

类工厂： 需要继承IClassFactory

class CFactory : public IClassFactory {
public:virtual HRESULT __stdcall QueryInterface(const IID& iid, void** ppv);virtual ULONG __stdcall AddRef();virtual ULONG __stdcall Release();virtual HRESULT __stdcall CreateInstance(IUnknown* pUnknownOuter,const IID& IID,void** ppv);virtual HRESULT __stdcall LockServer(BOOL block);CFactory() : m_cRef(1) {}~CFactory() {trace("class CFactory: destroyed...");}
private:long  m_cRef;
};

然而，我们仍然需要将其称为合法的DLL COM服务器，要实现的函数包括

DllMain,DllGetClassObject,DllCanUnloadNow,DllRegisterServer,DllUnRegisterServer,

这些都是API式函数，是直接调用，而不是通过COM接口调用。

实现如下：

STDAPI DllCanUnloadNow() {if((g_cComponents == 0) && (g_cServerLock == 0)) {return S_OK;}else {return S_FALSE;}
}STDAPI DllGetClassObject(const IID &clsid, const IID &riid, void** ppv) {trace("DllGetClassObject: create class factory");if(clsid != CLSID_CB) {return CLASS_E_CLASSNOTAVAILABLE;}CFactory* pFactory = new CFactory;if(pFactory == NULL) {return E_OUTOFMEMORY;}HRESULT hr = pFactory->QueryInterface(riid, ppv);pFactory->Release();return hr;}STDAPI DllRegisterServer() {return S_OK;
}STDAPI DllUnregisterServer() {return S_OK;
}BOOL WINAPI DllMain(HANDLE hinstDLL, DWORD dwReason, LPVOID lpvReserved) {myHinstance = (HINSTANCE)hinstDLL;return TRUE;
}

值得注意的是DllGetClassObject 这个函数，有了这个方法才能在客户端与服务器端的通讯中得到类工厂。

并在CB.DEF中，定义DLL输出：

LIBRARY    "ComTestOne"EXPORTSDllCanUnloadNow        PRIVATEDllGetClassObject    PRIVATEDllRegisterServer    PRIVATEDllUnregisterServer  PRIVATE

最后，我们可以手动添加注册表，在注册表编辑器中我们添加组件的CSLID和dll 文件名：

至此，我们完成了服务器端。

在客户端，我们仅仅需要做的就是连接组件，在组件中得到接口进行调用即可：

int main() {CoInitialize(NULL);IY* iy = NULL;HRESULT hr = CoCreateInstance(CLSID_CB, NULL, CLSCTX_INPROC_SERVER, IID_IY, (void**)&iy);if(FAILED(hr)) {MessageBox(NULL, L"could not create instance", L"hello", MB_ICONWARNING | MB_CANCELTRYCONTINUE | MB_DEFBUTTON2);} else {iy->Fy();iy->Release();}cout << "--------------------------------------------------" << endl;IY* iy1 = NULL;HRESULT hr2 = CoCreateInstance(CLSID_CB, NULL, CLSCTX_INPROC_SERVER, IID_IY, (void**)&iy1);if(FAILED(hr2)) {MessageBox(NULL, L"could not create instance", L"hello", MB_ICONWARNING | MB_CANCELTRYCONTINUE | MB_DEFBUTTON2);} else {iy1->Fy();iy1->Release();}CoUninitialize();getchar();return 0;
}

CoCreateInstance(CLSID_CB, NULL, CLSCTX_INPROC_SERVER, IID_IY, (void**)&iy);

是最为重要的，我们必须了解其内部的工作原理，请参考：

http://benworld.iteye.com/blog/1988445

另外，需要把生成的ComTestOne.dll文件 拷贝到 客户端的DEBUG目录下。

运行效果如下：

在构建第一个实例时，会有划红线的重复现象出现，而构建第二个时则没有。

上传了 项目实例代码供参考。

附代码：CB.cpp

#include "CB.h"
#include <iostream>static long g_cServerLock = 0;
static long g_cComponents = 0;
static HINSTANCE myHinstance;CB::CB() : m_cRef(1){InterlockedIncrement(&g_cComponents);
}CB::~CB() {InterlockedDecrement(&g_cComponents);trace("class CB: destroyed...");
}HRESULT __stdcall CB::QueryInterface(const IID& iid, void** ppv) {if(iid == IID_IUnknown){trace("QueryInterface: Return pointer to IUnknown");*ppv = static_cast<IY *>(this);} else if(iid == IID_IY) {trace("QueryInterface: Return pointer to IY");*ppv = static_cast<IY *>(this);} else if(iid == IID_IZ) {trace("QueryInterface: Return pointer to IZ");*ppv = static_cast<IZ *>(this);}else {trace("QueryInterface: Return pointer to IUnknown");*ppv = NULL;return E_NOINTERFACE;}reinterpret_cast<IUnknown *> (*ppv)->AddRef();return S_OK;
}ULONG __stdcall CB::AddRef() {std::cout << "CB: m_Ref + 1 " << std::endl;return InterlockedIncrement(&m_cRef);
}ULONG __stdcall CB::Release() {std::cout << "CB: m_Ref - 1 " << std::endl;if(InterlockedDecrement(&m_cRef) == 0) {delete this;return 0;}return m_cRef;
}HRESULT __stdcall CB::Fy() {std::cout << "Fy" << std::endl;return S_OK;
}HRESULT __stdcall CB::Fz() {std::cout << "Fz" << std::endl;return S_OK;
}// class Factory IUnknown implementation
HRESULT __stdcall CFactory::QueryInterface(const IID& iid, void** ppv) {if((iid == IID_IUnknown) || (iid == IID_IClassFactory)) {// 将CFactory 转化为 ClassFactory*ppv = static_cast<IClassFactory*>(this);} else {*ppv = NULL;return E_NOINTERFACE;}reinterpret_cast<IUnknown*>(*ppv)->AddRef();return S_OK;
}ULONG __stdcall CFactory::AddRef() {std::cout << "CFactory: m_Ref + 1 " << std::endl;return InterlockedIncrement(&m_cRef);
}ULONG __stdcall CFactory::Release() {std::cout << "CFactory: m_Ref - 1 " << std::endl;if(InterlockedDecrement(&m_cRef) == 0) {delete this;return 0;}return m_cRef;
}HRESULT __stdcall CFactory::CreateInstance(IUnknown* pUnknownOuter,const IID& IID,void** ppv)
{trace("class factory : create component");if(pUnknownOuter != NULL) {return CLASS_E_NOAGGREGATION;}CB * pa = new CB;if(pa == NULL) {return E_OUTOFMEMORY;}HRESULT hr = pa->QueryInterface(IID, ppv);pa->Release();return hr;
}HRESULT __stdcall CFactory::LockServer(BOOL bLock) {if(bLock) {InterlockedIncrement(&g_cServerLock);} else {InterlockedDecrement(&g_cServerLock);}return S_OK;
}STDAPI DllCanUnloadNow() {if((g_cComponents == 0) && (g_cServerLock == 0)) {return S_OK;}else {return S_FALSE;}
}STDAPI DllGetClassObject(const IID &clsid, const IID &riid, void** ppv) {trace("DllGetClassObject: create class factory");if(clsid != CLSID_CB) {return CLASS_E_CLASSNOTAVAILABLE;}CFactory* pFactory = new CFactory;if(pFactory == NULL) {return E_OUTOFMEMORY;}HRESULT hr = pFactory->QueryInterface(riid, ppv);pFactory->Release();return hr;}STDAPI DllRegisterServer() {return S_OK;
}STDAPI DllUnregisterServer() {return S_OK;
}BOOL WINAPI DllMain(HANDLE hinstDLL, DWORD dwReason, LPVOID lpvReserved) {myHinstance = (HINSTANCE)hinstDLL;return TRUE;
}