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IWbemServices::GetObjectAsync method

The IWbemServices::GetObjectAsync method retrieves an object, either a class definition or instance, based on its path. This is similar to IWbemServices::GetObject except that the call returns immediately, and the object is provided to the supplied object sink.

Currently, this method retrieves objects only from the namespace associated with the IWbemServices pointer.

Syntax


HRESULT GetObjectAsync(
  [in]  const BSTR strObjectPath,
  [in]  LONG lFlags,
  [in]  IWbemContext *pCtx,
  [in]  IWbemObjectSink *pResponseHandler
);

Parameters

strObjectPath [in]

Path of the object to retrieve. For an instance provider, StrObjectPath can be in the following format:

  • Namespace:Class.Key = "Value"
  • Namespace:Class = "Value"
  • Namespace:Class.Key = "Value", Key2 = "Value2"

Specifying the namespace before the class is optional. Object paths without namespaces refer to instances in the current namespace. If necessary, you can substitute the single-quotation mark character (') for the double-quotation mark character (") to delimit the start and end of string property types.

If this is NULL, an empty object, which can become a new class, is returned. For more information, see Creating a Class.

lFlags [in]

The following flags affect the behavior of this method.

FlagMeaning
WBEM_FLAG_USE_AMENDED_QUALIFIERS

If this flag is set, WMI retrieves the amended qualifiers stored in the localized namespace of the current connection's locale. If not set, only the qualifiers stored in the immediate namespace are retrieved.

WBEM_FLAG_DIRECT_READ

This flag causes direct access to the provider for the class specified without any regard to its parent class or subclasses.

WBEM_FLAG_SEND_STATUS

Registers a request to receive intermediate status reports through the client's implementation of IWbemObjectSink::SetStatus. Provider implementation must support intermediate status reporting for this flag to change behavior.

 

pCtx [in]

Typically NULL. Otherwise, this is a pointer to an IWbemContext object that can be used by the provider that produces the requested class or instance. The values in the context object must be specified in the documentation for the provider in question. For more information about this parameter, see Making Calls to WMI.

pResponseHandler [in]

Pointer to the caller's implementation of IWbemObjectSink. This handler receives the requested object when it becomes available through the IWbemObjectSink::Indicate method. The pObjParam parameter contains the object. If any error code is returned, then the supplied IWbemObjectSink pointer is not used. If WBEM_S_NO_ERROR is returned, then the user's IWbemObjectSink implementation is called to indicate the result of the operation. Windows Management only calls AddRef to the pointer in cases where WBEM_S_NO_ERROR returns. In cases where an error code returns, the reference count is the same as on entry. For more information about this parameter, see Calling a Method.

Return value

This method returns an HRESULT that indicates the status of the method call. The following table lists the value contained within an HRESULT.

On failure, you can obtain any available information from the COM function GetErrorInfo.

COM-specific error codes can also be returned if network problems cause you to lose the remote connection to Windows Management.

Return codeDescription
WBEM_E_FAILED

Other error codes are returned asynchronously to the IWbemObjectSink.

WBEM_E_INVALID_PARAMETER

A specified parameter is not valid.

WBEM_E_INVALID_CLASS

The specified class does not exist.

WBEM_E_INVALID_OBJECT_PATH

The specified object path was not valid.

WBEM_S_NO_ERROR

The call succeeded.

WBEM_E_NOT_FOUND

The provider could not recognize the requested class.

WBEM_E_PROVIDER_NOT_CAPABLE

The provider could not retrieve the requested instance, even though the class name was recognized as being supplied by the provider.

WBEM_E_SHUTTING_DOWN

Windows Management service was probably stopped and restarted. A new call to ConnectServer is required.

 

Remarks

When implementing an instance provider, you should use the object path parser sample code in the WMI section of the PSDK to parse the object path for recognizing which object the client requests. Further, a provider that supports a derived class need only supply the values for the local properties of the class, rather than the inherited properties. WMI requests that the provider of the base class handle inherited properties.

When implementing a class provider, GetObjectAsync must determine which class is being requested by parsing the class name object path stored in the strObjectPath parameter. The GetObjectAsync method then either builds the class dynamically or takes the class from a private cache. Then, GetObjectAsync sends the class to WMI using the IWbemObjectSink pointer pointed to by the pResponseHandler parameter. The IWbemObjectSink::SetStatus method is called to indicate the end of the result set. It can also be called with no intervening calls to IWbemObjectSink::Indicate if error conditions occur.

Because the call-back might not be returned at the same authentication level as the client requires, it is recommended that you use semisynchronous instead of asynchronous communication. If you require asynchronous communication, see Calling a Method.

For more information about using methods semisynchronously, see IWbemServices::GetObject and Calling a Method.

Examples

The following example describes how to implement GetObjectAsync for an instance provider.


SCODE CInstPro::GetObjectAsync (BSTR ObjectPath, 
                                long lFlags, IWbemContext *pCtx,
                                IWbemObjectSink FAR* pHandler)
{
    ULONG cRef;         // Reference count
    SCODE sc;
    BOOL bOK = FALSE;

    IWbemServices *  m_pNamespace;
    IWbemClassObject FAR* pObj;

    // Check arguments.

    if(ObjectPath == NULL || pHandler == NULL ||
        m_pNamespace == NULL)
        return WBEM_E_INVALID_PARAMETER;

    
    // Based on the object path, produce an empty instance
    // of the class and gather required data,
    // setting the instance's property values accordingly.
    // This example assumes that GetByPath is implemented
    // by the provider to do this.
    // The IWbemPath interface can be used to parse
    // the object path, separating the namespace and class name.

    sc = GetByPath (ObjectPath, &pObj, pCtx);
    if(sc == S_OK) 
    {
        pHandler->Indicate (1, &pObj);
        pObj->Release();
        bOK = TRUE;
    }

    sc = (bOK) ? S_OK : WBEM_E_NOT_FOUND;

    // Set status.

    pHandler->SetStatus(0,sc, NULL, NULL);

    // Free memory resources.

    SysFreeString(ObjectPath);
    m_pNamespace->Release();
    pObj->Release();

    return sc;
  
}

The following example shows how a typical class provider implements GetObjectAsync.


HRESULT CStdProvider::GetObjectAsync( 
            /* [in] */ BSTR strObjectPath,
            /* [in] */ long lFlags,
            /* [in] */ IWbemContext __RPC_FAR *pCtx,
            /* [in] */ IWbemObjectSink __RPC_FAR *pResponseHandler
            )
{

    IWbemClassObject *pClass = 0;

// Assume there is an IWbemServices pointer available.
// Retrieve an 'empty' object which is built up
// into the class definition.

    HRESULT hRes = m_pSvc->GetObject(NULL, 0, NULL, &pClass, 0);
    if (hRes)
        return hRes;

// Parse the object path and determine which class is   
// required. The path string is the required class name.
// Fill in the properties required for the class definition
// using pClass->Put(...), and so on.

    
    // ...

    // Send the class definition back to WMI.
    pResponseHandler->Indicate(1, &pClass);

// Indicate that it is now finished.

    pResponseHandler->SetStatus(0, WBEM_S_NO_ERROR, 0, 0);
    SysFreeString(strObjectPath);
    m_pSvc->Relaase();
    pClass->Release();  // This is no longer needed.
    return WBEM_S_NO_ERROR;
}

Requirements

Minimum supported client

Windows Vista

Minimum supported server

Windows Server 2003

Header

Wbemcli.h (include Wbemidl.h)

Library

Wbemuuid.lib

DLL

Fastprox.dll;
Esscli.dll;
Framedyn.dll;
Ntevt.dll;
Stdprov.dll;
Viewprov.dll;
Wbemcomn.dll;
Wbemcore.dll;
Wbemess.dll;
Wbemsvc.dll;
Wmipicmp.dll;
Wmidcprv.dll;
Wmipjobj.dll;
Wmiprvsd.dll

See also

IWbemServices
Describing the Location of a WMI Object
Creating a Class
Calling a Method
IWbemServices::GetObject

 

 

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