（WMI）ExecMethod输出参数 - 无论调用结果如何，ResultingSnapshot都为NULL，为什么？

Question

我正在使用WMI创建RCT检查点。以下是代码段。问题是，当我使用Create Snapshott调用方法ExecMethod时，检查点被创建，但ResultingSnapshot仍然指向NULL。

由于调用是异步的（因为pOutParameters的返回值是4096）我也一直等到WaitForJobCompletion完成了工作，但pOutParameters没有更新，仍然，ResultingSnapshot为NULL。

基本上，我需要这个ResultingSnapshot来创建一个参考点。如果还有其他方法可以做，我可以写它，但需要指导。

我是WMI的新手，任何帮助或领导都表示赞赏。

HRESULT hr;
CComPtr<IWbemClassObject> pInParams;
CComPtr<IWbemClassObject> pOutParameters;
IWbemCallResult *pResult = 0;

// Set Method Paramters
this->GetMethodParams(L"Msvm_VirtualSystemSnapshotService", L"CreateSnapshot", &pInParams);

IWbemClassObject * pVirtualSystemSnaphotSettingData = NULL;
hr = m_pWbemServices->GetObject(L"Msvm_VirtualSystemSnapshotSettingData", 0, NULL, &pVirtualSystemSnaphotSettingData, &pResult);

IWbemClassObject * pInpInstOfSnapshotSettingData = NULL;
hr = pVirtualSystemSnaphotSettingData->SpawnInstance(0, &pInpInstOfSnapshotSettingData);

VARIANT consistencyLevel;
VariantInit(&consistencyLevel);
V_VT(&consistencyLevel) = VT_BSTR;
V_BSTR(&consistencyLevel) = SysAllocString(L"1");
hr = pInpInstOfSnapshotSettingData->Put(L"ConsistencyLevel", 0, &consistencyLevel, 0);
VariantClear(&consistencyLevel);

VARIANT elementName;
VariantInit(&elementName);
V_VT(&elementName) = VT_BSTR;
V_BSTR(&elementName) = SysAllocString(L"rhel-1");
hr = pInpInstOfSnapshotSettingData->Put(L"ElementName", 0, &elementName, 0);
VariantClear(&elementName);

hr = m_pWbemServices->PutInstance(pInpInstOfSnapshotSettingData, 0, NULL, &pResult);

BSTR objString = NULL;
hr = pInpInstOfSnapshotSettingData->GetObjectText(0, &objString);
BSTR ArgNameTwo = SysAllocString(L"SnapshotSettings");
VARIANT v;
V_VT(&v) = VT_BSTR;
V_BSTR(&v) = objString; 

hr = pInParams->Put(ArgNameTwo, 0, &v, 0);

VARIANT vtProp;
m_pVmWbemClassObject->Get(L"__Path", 0, &vtProp, 0, 0);

wprintf(L"Affected System : : %ls", (LPWSTR)vtProp.bstrVal);
HRESULT hres = pInParams->Put(L"AffectedSystem", 0 , &vtProp, NULL);

VARIANT var;
VariantInit(&var);
V_VT(&var) = VT_BSTR;
V_BSTR(&var) = SysAllocString(L"2");


CHK_HRES(pInParams->Put(L"SnapshotType", 0, &var, 0));


IEnumWbemClassObject* pEnumOb = NULL;
hr = m_pWbemServices->ExecQuery(
BSTR(L"WQL"),
BSTR(L"select * from Msvm_VirtualSystemSnapshotService"),
WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
NULL,
&pEnumOb);
IWbemClassObject *pclsObj1 = NULL;
ULONG uReturn1 = 0;

while (1)
{
    HRESULT hr = pEnumOb->Next(WBEM_INFINITE, 1, &pclsObj1, &uReturn1);

    if (0 == uReturn1)
    {
        break;
    }

    IWbemCallResult *pCallResult = NULL;
    IWbemClassObject *pResObj = NULL;

    CComBSTR path(this->GetStrProperty(L"__PATH", pclsObj1));

    hr = m_pWbemServices->ExecMethod(path, L"CreateSnapshot", 0, NULL, pInParams, &pOutParameters, &pCallResult);



    /* cout << "check1 : " << hex << hr << endl;
    hr = pCallResult->GetResultObject(0, &pResObj);
    cout << "check2" << endl;*/

    this->WaitForJobCompletion(pOutParameters);
   }

cout << "\nSnpshot Complete" << endl;
}

编辑我发现SnapshotType参数设置不正确它应该是32768我已经使用以下方式将uint16转换为Variant但没有成功，我得到0x80070057 Incorrect Parameter错误。

VARIANT var;
VariantInit(&var);
V_VT(&var) = VT_BSTR;
V_BSTR(&var) = SysAllocString(L"32768");

hr = pInParams->Put(L"SnapshotType", 0, &var, CIM_UINT16);

Answer 1

HRESULT GetRelated(PWSTR sAssociatePath, PWSTR sResultClass, IWbemClassObject** ppResultObject)
{
CStringW query;
query.Format(L"associators of {%s} where ResultClass = %s", sAssociatePath, sResultClass);

CComPtr<IEnumWbemClassObject> pEnumOb;

HRESULT hr = m_pWbemServices->ExecQuery(
    BSTR(L"WQL"),
    CComBSTR(query),
    WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
    NULL,
    &pEnumOb));
ULONG uReturn = 0;
CComPtr<IWbemClassObject> pObject;
hr = pEnumOb->Next(WBEM_INFINITE, 1, &pObject, &uReturn);
return hr;
}
// Call the GetRelated function above with the __PATH parameter of JOB
CComPtr<IWbemClassObject> pOutParam = NULL;
CHK_HRES(this->ExecMethod(pHyperVObject, L"ConvertToReferencePoint", pInParams, &pOutParam, NULL));
CComVariant jobPath;
CHK_HRES(pOutParam->Get(L"Job", 0, &jobPath, NULL, NULL));
CComPtr<IWbemClassObject> pResult;
GetRelated(jobPath.bstrVal, L"Msvm_VirtualSystemReferencePoint", &pResult);

Answer 2

您提供了ppCallResult参数。来自documentation：

ppCallResult [out]如果为NULL，则不使用。如果指定了ppCallResult，则必须将其设置为在进入时指向NULL。在这种情况下，调用立即返回WBEM_S_NO_ERROR。 ppCallResult参数接收指向新IWbemCallResult对象的指针，必须轮询该对象以使用GetCallStatus方法获取方法执行的结果。通过调用IWbemCallResult :: GetResultObject可以获得调用的out参数。

因此，您需要在GetCallStatus上使用pCallResult，直到方法完成，然后GetResultObject获取out参数：

LONG status;
while ((hr = pCallResult->GetCallStatus(1000, &status)) == WBEM_S_TIMEDOUT);
/* check hr and status here */
hr = pCallResult->GetResultObject(0, &pResObj);

或使用WBEM_INFINITE：

LONG status;
hr = pCallResult->GetCallStatus(WBEM_INFINITE, &status);
/* check hr and status here */
hr = pCallResult->GetResultObject(0, &pResObj);

或者提供NULL而不是pCallResult，它将是一个同步调用，其中将设置pOutParameters：

hr = m_pWbemServices->ExecMethod(path, L"CreateSnapshot", 0, NULL, pInParams, &pOutParameters, NULL);