示例:异步从本地计算机获取 WMI 数据

可以使用本主题中的过程和代码示例创建一个完整的 WMI 客户端应用程序,该应用程序执行 COM 初始化,连接到本地计算机上的 WMI,异步获取数据,然后清理。 本示例获取本地计算机上的操作系统的名称并显示它。

以下过程用于执行 WMI 应用程序。 步骤 1 到 5 包含设置和连接到 WMI 所需的所有步骤,步骤 6 和 7 是异步检索操作系统名称的位置。

从本地计算机异步获取 WMI 数据

  1. 使用调用 CoInitializeEx 初始化 COM 参数。

    有关详细信息,请参阅 初始化 WMI 应用程序的 COM

  2. 通过调用 CoInitializeSecurity 初始化 COM 进程安全性。

    有关详细信息,请参阅 使用 C++ 设置默认进程安全级别

  3. 通过调用 CoCreateInstance 获取 WMI 的初始定位符。

    有关详细信息,请参阅 创建与 WMI 命名空间的连接

  4. 通过调用 IWbemLocator::ConnectServer 获取指向本地计算机上的 root\cimv2 命名空间的 IWbemServices 的指针。 有关如何连接到远程计算机的详细信息,请参阅 示例:从远程计算机获取 WMI 数据

    有关详细信息,请参阅 创建与 WMI 命名空间的连接

  5. 设置 IWbemServices 代理安全性,以便 WMI 服务可以通过调用 CoSetProxyBlanket 模拟客户端。

    有关详细信息,请参阅 在 WMI 连接上设置安全级别

  6. 使用 IWbemServices 指针向 WMI 发出请求。 此示例使用 IWbemServices::ExecQueryAsync 方法异步接收数据。 每当异步接收数据时,都必须提供 IWbemObjectSink 的实现。 此示例提供 QuerySink 类中的实现。 此类的实现代码和头文件代码遵循主要示例提供。 每当收到数据时 ,IWbemServices::ExecQueryAsync 方法将调用 QuerySink::Indicate 方法。

    有关如何创建 WMI 请求的详细信息,请参阅操作类和实例信息和调用方法

  7. 等待异步检索数据。 使用 IWbemServices::CancelAsyncCall 方法手动停止异步调用。

下面的代码示例异步从本地计算机获取 WMI 数据。

#include "querysink.h"


int main(int argc, char **argv)
{
    HRESULT hres;

    // Step 1: --------------------------------------------------
    // Initialize COM. ------------------------------------------

    hres =  CoInitializeEx(0, COINIT_MULTITHREADED); 
    if (FAILED(hres))
    {
        cout << "Failed to initialize COM library. Error code = 0x" 
            << hex << hres << endl;
        return 1;                  // Program has failed.
    }

    // Step 2: --------------------------------------------------
    // Set general COM security levels --------------------------

    hres =  CoInitializeSecurity(NULL, 
                                 -1,                          // COM authentication
                                 NULL,                        // Authentication services
                                 NULL,                        // Reserved
                                 RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication 
                                 RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation  
                                 NULL,                        // Authentication info
                                 EOAC_NONE,                   // Additional capabilities 
                                 NULL);                       // Reserved

                      
    if (FAILED(hres))
    {
        cout << "Failed to initialize security. Error code = 0x" 
            << hex << hres << endl;
        CoUninitialize();
        return 1;                    // Program has failed.
    }
    
    // Step 3: ---------------------------------------------------
    // Obtain the initial locator to WMI -------------------------

    IWbemLocator *pLoc = NULL;

    hres = CoCreateInstance(
        CLSID_WbemLocator,             
        0, 
        CLSCTX_INPROC_SERVER, 
        IID_IWbemLocator, (LPVOID *) &pLoc);
 
    if (FAILED(hres))
    {
        cout << "Failed to create IWbemLocator object."
            << " Err code = 0x"
            << hex << hres << endl;
        CoUninitialize();
        return 1;                 // Program has failed.
    }

    // Step 4: -----------------------------------------------------
    // Connect to WMI through the IWbemLocator::ConnectServer method

    IWbemServices *pSvc = NULL;
 
    // Connect to the local root\cimv2 namespace
    // and obtain pointer pSvc to make IWbemServices calls.
    hres = pLoc->ConnectServer(_bstr_t(L"ROOT\\CIMV2"), 
                               NULL,
                               NULL,
                               0,
                               NULL,
                               0,
                               0, 
                               &pSvc);
    
    if (FAILED(hres))
    {
        cout << "Could not connect. Error code = 0x" 
             << hex << hres << endl;
        pLoc->Release();     
        CoUninitialize();
        return 1;                // Program has failed.
    }

    cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;


    // Step 5: --------------------------------------------------
    // Set security levels on the proxy -------------------------

    hres = CoSetProxyBlanket(pSvc,                        // Indicates the proxy to set
                             RPC_C_AUTHN_WINNT,           // RPC_C_AUTHN_xxx
                             RPC_C_AUTHZ_NONE,            // RPC_C_AUTHZ_xxx
                             NULL,                        // Server principal name 
                             RPC_C_AUTHN_LEVEL_CALL,      // RPC_C_AUTHN_LEVEL_xxx 
                             RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
                             NULL,                        // client identity
                             EOAC_NONE);                  // proxy capabilities 

    if (FAILED(hres))
    {
        cout << "Could not set proxy blanket. Error code = 0x" 
            << hex << hres << endl;
        pSvc->Release();
        pLoc->Release();     
        CoUninitialize();
        return 1;               // Program has failed.
    }

    // Step 6: --------------------------------------------------
    // Use the IWbemServices pointer to make requests of WMI ----

    // For example, get the name of the operating system.
    // The IWbemService::ExecQueryAsync method will call
    // the QuerySink::Indicate method when it receives a result
    // and the QuerySink::Indicate method will display the OS name
    QuerySink* pResponseSink = new QuerySink();
    pResponseSink->AddRef();
    hres = pSvc->ExecQueryAsync(bstr_t("WQL"), 
                                bstr_t("SELECT * FROM Win32_OperatingSystem"),
                                WBEM_FLAG_BIDIRECTIONAL, 
                                NULL,
                                pResponseSink);
    
    if (FAILED(hres))
    {
        cout << "Query for operating system name failed."
            << " Error code = 0x" 
            << hex << hres << endl;
        pSvc->Release();
        pLoc->Release();
        pResponseSink->Release();
        CoUninitialize();
        return 1;               // Program has failed.
    }

    // Step 7: -------------------------------------------------
    // Wait to get the data from the query in step 6 -----------
    Sleep(500);
    pSvc->CancelAsyncCall(pResponseSink);

    // Cleanup
    // ========
    pSvc->Release();
    pLoc->Release();
    CoUninitialize();

    return 0;   // Program successfully completed.
 
}

以下头文件用于 QuerySink 类。 在前面的代码示例中使用 QuerySink 类。

// QuerySink.h
#ifndef QUERYSINK_H
#define QUERYSINK_H

#define _WIN32_DCOM
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>

#pragma comment(lib, "wbemuuid.lib")

class QuerySink : public IWbemObjectSink
{
    LONG m_lRef;
    bool bDone;
 CRITICAL_SECTION threadLock; // for thread safety

public:
    QuerySink() { m_lRef = 0; bDone = false; 
     InitializeCriticalSection(&threadLock); }
    ~QuerySink() { bDone = true;
        DeleteCriticalSection(&threadLock); }

    virtual ULONG STDMETHODCALLTYPE AddRef();
    virtual ULONG STDMETHODCALLTYPE Release();        
    virtual HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid,
        void** ppv);

    virtual HRESULT STDMETHODCALLTYPE Indicate( 
            LONG lObjectCount,
            IWbemClassObject __RPC_FAR *__RPC_FAR *apObjArray
            );
        
    virtual HRESULT STDMETHODCALLTYPE SetStatus( 
            /* [in] */ LONG lFlags,
            /* [in] */ HRESULT hResult,
            /* [in] */ BSTR strParam,
            /* [in] */ IWbemClassObject __RPC_FAR *pObjParam
            );

 bool IsDone();
};

#endif    // end of QuerySink.h

下面的代码示例是 QuerySink 类的实现。

// QuerySink.cpp
#include "querysink.h"

ULONG QuerySink::AddRef()
{
    return InterlockedIncrement(&m_lRef);
}

ULONG QuerySink::Release()
{
    LONG lRef = InterlockedDecrement(&m_lRef);
    if(lRef == 0)
        delete this;
    return lRef;
}

HRESULT QuerySink::QueryInterface(REFIID riid, void** ppv)
{
    if (riid == IID_IUnknown || riid == IID_IWbemObjectSink)
    {
        *ppv = (IWbemObjectSink *) this;
        AddRef();
        return WBEM_S_NO_ERROR;
    }
    else return E_NOINTERFACE;
}


HRESULT QuerySink::Indicate(long lObjectCount,
    IWbemClassObject **apObjArray)
{
 HRESULT hres = S_OK;

    for (int i = 0; i < lObjectCount; i++)
    {
        VARIANT varName;
        hres = apObjArray[i]->Get(_bstr_t(L"Name"),
            0, &varName, 0, 0);

        if (FAILED(hres))
        {
            cout << "Failed to get the data from the query"
                << " Error code = 0x"
                << hex << hres << endl;
            return WBEM_E_FAILED;       // Program has failed.
        }

        printf("Name: %ls\n", V_BSTR(&varName));
    }

    return WBEM_S_NO_ERROR;
}

HRESULT QuerySink::SetStatus(
            /* [in] */ LONG lFlags,
            /* [in] */ HRESULT hResult,
            /* [in] */ BSTR strParam,
            /* [in] */ IWbemClassObject __RPC_FAR *pObjParam
        )
{
 if(lFlags == WBEM_STATUS_COMPLETE)
 {
  printf("Call complete.\n");

  EnterCriticalSection(&threadLock);
  bDone = true;
  LeaveCriticalSection(&threadLock);
 }
 else if(lFlags == WBEM_STATUS_PROGRESS)
 {
  printf("Call in progress.\n");
 }
    
    return WBEM_S_NO_ERROR;
}


bool QuerySink::IsDone()
{
    bool done = true;

 EnterCriticalSection(&threadLock);
 done = bDone;
 LeaveCriticalSection(&threadLock);

    return done;
}    // end of QuerySink.cpp