示例:调用提供程序方法

您可以使用本主题中的过程和代码示例来创建完整的 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、调用提供程序方法,然后清除。 Win32 _ Process:: Create方法用于在新进程中启动 Notepad.exe。

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,6是调用提供程序方法的位置。

调用提供程序方法

  1. 通过调用 CoInitializeEx初始化 COM 参数。

    有关详细信息,请参阅为 WMI 应用程序初始化 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根 cimv2 命名空间的 IWbemServices 的指针。 若要连接到远程计算机,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 proxy security,以便 WMI 服务可以通过调用 CoSetProxyBlanket来模拟客户端。

    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:: ExecMethod 来调用提供程序方法 Win32 _ Process:: Create

    有关向 WMI 发出请求的详细信息,请参阅 操作类和实例信息调用方法

    如果提供程序方法有任何 in 参数或 out 参数,则必须将参数的值提供给 IWbemClassObject 指针。 对于 in 参数,必须生成参数内定义的实例,然后设置这些新实例的值。 Win32 _ Process:: Create方法要求 命令行 内参数中的值才能正常执行。

    下面的代码示例创建一个 IWbemClassObject 指针,生成 Win32 进程的新实例 _ ::创建 参数内定义,然后将 命令行 内参数的值设置为 Notepad.exe。

    // Set up to call the Win32_Process::Create method
    BSTR MethodName = SysAllocString(L"Create");
    BSTR ClassName = SysAllocString(L"Win32_Process");
    
    IWbemClassObject* pClass = NULL;
    hres = pSvc->GetObject(ClassName, 0, NULL, &pClass, NULL);
    
    IWbemClassObject* pInParamsDefinition = NULL;
    hres = pClass->GetMethod(MethodName, 0, 
        &pInParamsDefinition, NULL);
    
    IWbemClassObject* pClassInstance = NULL;
    hres = pInParamsDefinition->SpawnInstance(0, &pClassInstance);
    
    // Create the values for the in-parameters
    VARIANT varCommand;
    varCommand.vt = VT_BSTR;
    varCommand.bstrVal = _bstr_t(L"notepad.exe");
    
    // Store the value for the in-parameters
    hres = pClassInstance->Put(L"CommandLine", 0,
        &varCommand, 0);
    wprintf(L"The command is: %s\n", V_BSTR(&varCommand));
    

    下面的代码示例演示如何将 Win32 _ 进程:: Create 方法 out 参数提供给 IWbemClassObject 指针。 使用 IWbemClassObject:: Get 方法获取输出参数值,并将其存储在 变量变量中 ,以便可以向用户显示该参数值。

    // Execute Method
    IWbemClassObject* pOutParams = NULL;
    hres = pSvc->ExecMethod(ClassName, MethodName, 0,
        NULL, pClassInstance, &pOutParams, NULL);
    
    VARIANT varReturnValue;
    hres = pOutParams->Get(_bstr_t(L"ReturnValue"), 0, 
        &varReturnValue, NULL, 0);
    

下面的代码示例演示如何使用 WMI 调用提供程序方法。

#define _WIN32_DCOM

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

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

int main(int iArgCnt, 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 negotiates service
        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 for 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 ----

    // set up to call the Win32_Process::Create method
    BSTR MethodName = SysAllocString(L"Create");
    BSTR ClassName = SysAllocString(L"Win32_Process");

    IWbemClassObject* pClass = NULL;
    hres = pSvc->GetObject(ClassName, 0, NULL, &pClass, NULL);

    IWbemClassObject* pInParamsDefinition = NULL;
    hres = pClass->GetMethod(MethodName, 0, 
        &pInParamsDefinition, NULL);

    IWbemClassObject* pClassInstance = NULL;
    hres = pInParamsDefinition->SpawnInstance(0, &pClassInstance);

    // Create the values for the in parameters
    VARIANT varCommand;
    varCommand.vt = VT_BSTR;
    varCommand.bstrVal = _bstr_t(L"notepad.exe");

    // Store the value for the in parameters
    hres = pClassInstance->Put(L"CommandLine", 0,
        &varCommand, 0);
    wprintf(L"The command is: %s\n", V_BSTR(&varCommand));

    // Execute Method
    IWbemClassObject* pOutParams = NULL;
    hres = pSvc->ExecMethod(ClassName, MethodName, 0,
    NULL, pClassInstance, &pOutParams, NULL);

    if (FAILED(hres))
    {
        cout << "Could not execute method. Error code = 0x" 
             << hex << hres << endl;
        VariantClear(&varCommand);
        SysFreeString(ClassName);
        SysFreeString(MethodName);
        pClass->Release();
        pClassInstance->Release();
        pInParamsDefinition->Release();
        pOutParams->Release();
        pSvc->Release();
        pLoc->Release();
        CoUninitialize();
        return 1;               // Program has failed.
    }

    // To see what the method returned,
    // use the following code.  The return value will
    // be in &varReturnValue
    VARIANT varReturnValue;
    hres = pOutParams->Get(_bstr_t(L"ReturnValue"), 0, 
        &varReturnValue, NULL, 0);


    // Clean up
    //--------------------------
    VariantClear(&varCommand);
    VariantClear(&varReturnValue);
    SysFreeString(ClassName);
    SysFreeString(MethodName);
    pClass->Release();
    pClassInstance->Release();
    pInParamsDefinition->Release();
    pOutParams->Release();
    pLoc->Release();
    pSvc->Release();
    CoUninitialize();
    return 0;
}