如何在com接口中传递类？在线等待

Question

我在一个COM的接口函数中返回一个类，应用程序调用此COM接口如何获取此返回的类？直接在接口参数中将返回值定义成我要返回的类编译不会通过，我是用IDispatch将此类返回的，但是在应用程序调用时此接口返回IDispatch**，再转换为我要的类时没有出错，但是在调用这个类的方法时出现异常。
COM接口的代码是：
[id(22), helpstring("设计DTS包类的属性")] HRESULT GetDTSPackage2([out, retval]IDispatch **pPackage2);STDMETHODIMP CDTSPackage2::GetDTSPackage2(IDispatch **pPackage2)
{
AFX_MANAGE_STATE(AfxGetStaticModuleState()) CoInitialize(NULL);
_Package2 objPackage2;
if (!objPackage2.CreateDispatch("DTS.Package2"))
{
m_dwErrorNumber = ERROR_PACKAGE2CREATEDISPATCH;
*pPackage2 = NULL;
return S_OK;
} try
{
objPackage2.SetName(m_dtsPackage2.szPackageName);
objPackage2.SetWriteCompletionStatusToNTEventLog(m_dtsPackage2.bWriteCompletionStatusToNTEventLog);
objPackage2.SetFailOnError(m_dtsPackage2.bFailOnError);
objPackage2.SetPackagePriorityClass(m_dtsPackage2.lPackagePriorityClass);
objPackage2.SetMaxConcurrentSteps(m_dtsPackage2.lMaxConcurrentSteps);
objPackage2.SetLineageOptions(m_dtsPackage2.lLineageOptions);
objPackage2.SetUseTransaction(m_dtsPackage2.bUseTransaction);
objPackage2.SetTransactionIsolationLevel(m_dtsPackage2.lTransactionIsolationLevel);
objPackage2.SetAutoCommitTransaction(m_dtsPackage2.bAutoCommitTransaction);
objPackage2.SetRepositoryMetadataOptions(m_dtsPackage2.lRepositoryMetadataOptions);
objPackage2.SetUseOLEDBServiceComponents(m_dtsPackage2.bUseOLEDBServiceComponents);
objPackage2.SetLogToSQLServer(m_dtsPackage2.bLogToSQLServer);
objPackage2.SetLogServerFlags(m_dtsPackage2.lLogServerFlags);
objPackage2.SetFailPackageOnLogFailure(m_dtsPackage2.bFailPackageOnLogFailure);
objPackage2.SetExplicitGlobalVariables(m_dtsPackage2.bExplicitGlobalVariables);
objPackage2.SetPackageType(m_dtsPackage2.lPackageType);
////////////////////
objPackage2.SetDescription(m_dtsPackage2.szDescription);
objPackage2.SetLogFileName(m_dtsPackage2.szLogFileName);
objPackage2.SetLogServerName(m_dtsPackage2.szLogServerName);
objPackage2.SetLogServerPassword(m_dtsPackage2.szLogServerPassword);
objPackage2.SetLogServerUserName(m_dtsPackage2.szLogServerPassword);
}
catch (_com_error &e)
{
*pPackage2 = NULL;
PrintComError(e);
m_dwErrorNumber = ERROR_PACKAGE2CREATEDISPATCH;
return S_OK;
} m_dwErrorNumber = 0;
*pPackage2 = objPackage2;
memset(&m_dtsPackage2, 0, sizeof(m_dtsPackage2));
return S_OK;
}

Answer 1

应用程序代码是：
void CTestWorkformSystemDlg::OnBtndtsinterface() 
{
CoInitialize(NULL);
IDTSPackage2 *pPack = NULL;
IDTSConnection2 *pConn1 = NULL;
IDTSConnection2 *pConn2 = NULL;
IDTSStep *pStep = NULL;
IDTSDataPumpTask *pTask = NULL;
IDTSOleDBProperty2 *pProp2 = NULL;
IDTSTransformation2 *pTran = NULL;
IDTSColumn *pCol1 = NULL;
IDTSColumn *pCol2 = NULL;

HRESULT ret = CoCreateInstance(
CLSID_DTSPackage2,
NULL,
CLSCTX_ALL,
IID_IDTSPackage2,
(LPVOID *)&pPack
); ret = CoCreateInstance(
CLSID_DTSConnection2,
NULL,
CLSCTX_ALL,
IID_IDTSConnection2,
(LPVOID *)&pConn1
); ret = CoCreateInstance(
CLSID_DTSConnection2,
NULL,
CLSCTX_ALL,
IID_IDTSConnection2,
(LPVOID *)&pConn2
); ret = CoCreateInstance(
CLSID_DTSStep,
NULL,
CLSCTX_ALL,
IID_IDTSStep,
(LPVOID *)&pStep
); ret = CoCreateInstance(
CLSID_DTSDataPumpTask,
NULL,
CLSCTX_ALL,
IID_IDTSDataPumpTask,
(LPVOID *)&pTask
); ret = CoCreateInstance(
CLSID_DTSOleDBProperty2,
NULL,
CLSCTX_ALL,
IID_IDTSOleDBProperty2,
(LPVOID *)&pProp2
); ret = CoCreateInstance(
CLSID_DTSTransformation2,
NULL,
CLSCTX_ALL,
IID_IDTSTransformation2,
(LPVOID *)&pTran
); ret = CoCreateInstance(
CLSID_DTSColumn,
NULL,
CLSCTX_ALL,
IID_IDTSColumn,
(LPVOID *)&pCol1
); ret = CoCreateInstance(
CLSID_DTSColumn,
NULL,
CLSCTX_ALL,
IID_IDTSColumn,
(LPVOID *)&pCol2
);

pPack->put_bAutoCommitTransaction(TRUE);
pPack->put_bExplicitGlobalVariables(TRUE);
pPack->put_bFailOnError(TRUE);
pPack->put_bFailPackageOnLogFailure(TRUE);
pPack->put_bLogToSQLServer(FALSE);
pPack->put_bUseOLEDBServiceComponents(TRUE);
pPack->put_bUseTransaction(TRUE);
pPack->put_bWriteCompletionStatusToNTEventLog(FALSE);
pPack->put_lLineageOptions(0);
pPack->put_lLogServerFlags(0);
pPack->put_lMaxConcurrentSteps(4);
pPack->put_lPackagePriorityClass(2);
pPack->put_lPackageType(0);
pPack->put_lRepositoryMetadataOptions(0);
pPack->put_lTransactionIsolationLevel(4096);
pPack->put_szDescription(L"向远程服务器导数据");
pPack->put_szLogFileName(L"c:\\logfile.txt");
pPack->put_szLogServerName(L"");
pPack->put_szLogServerPassword(L"");
pPack->put_szLogServerUserName(L"");
pPack->put_szPackageName(L"批量数据导入");
IDispatch* obj = NULL;
pPack->GetDTSPackage2(&obj);
_Package2 objpak2;
// BOOL bRet = objpak2.CreateDispatch("DTS.Package2");
objpak2.AttachDispatch(obj);
CString str = objpak2.GetDescription();　　　　　　　　//这句出错
// objpak2.m_lpDispatch = obj; Connections objConns(objpak2.GetConnections());　　　　//这句出错
Connection2* objConn1 = NULL; pProp2->put_lColumnLengths(11);
pProp2->put_lFileFormat(1);
pProp2->put_lFileType(1);
pProp2->put_lMaxCharactersPerDelimitedColumn(255);
pProp2->put_lMode(1);
pProp2->put_lSkipRows(0);
pProp2->put_lNumberofColumn(1);
pProp2->put_szColumnDelimiter(L"|");
pProp2->put_szDataSource(L"c:\\bbb.txt");
pProp2->put_szRowDelimiter(L"\r\n");
pProp2->put_szTextQualifier(L"\"");
pProp2->put_bFirstRowColumnName(FALSE); pConn1->put_lConnectionId(1);
pConn1->put_bReusable(TRUE);
pConn1->put_szConnectionName(L"TextFile");
pConn1->put_bUseDSL(FALSE);
pConn1->put_bConnectImmediate(FALSE);
pConn1->put_lConnectionTimeout(60);
pConn1->put_bUseTrustedConnection(FALSE);
pConn1->put_szDataSource(L"c:\\bbb.txt"); pPack->GetDTSFlatFileConnection2(pProp2, pConn1, (IDispatch *)&objConns, &obj);
// objConn1 = (Connection2 *)obj;
objConns.Add(obj); Connection2* objConn2 = NULL;
pConn2->put_lConnectionId(2);
pConn2->put_bReusable(TRUE);
pConn2->put_szConnectionName(L"pubcon");
pConn2->put_bUseDSL(FALSE);
pConn2->put_bConnectImmediate(FALSE);
pConn2->put_lConnectionTimeout(60);
pConn2->put_bUseTrustedConnection(FALSE);
pConn2->put_szDataSource(L"TRASIN-GUOYONG");
pConn2->put_szCatalog(L"pubs");
pConn2->put_szUserID(L"sa");
pConn2->put_szPassword(L"gisterguoyong");
pPack->GetSQLOLEDBConnection2((IDispatch *)&objConns, pConn2, &obj);
// objConn2 = (Connection2 *)obj;
objConns.Add(obj);
Steps objSteps(objpak2.GetSteps());
pStep->put_bAddGlobalVariables(TRUE);
pStep->put_bCloseConnection(TRUE);
pStep->put_bCommitSuccess(FALSE);
pStep->put_bDisableStep(FALSE);
pStep->put_bExecuteInMainThread(TRUE);
pStep->put_bFailPackageOnError(FALSE);
pStep->put_bIsPackageDSORowset(FALSE);
pStep->put_bJoinTransactionIfPresent(FALSE);
pStep->put_bRollbackFailure(FALSE);
pStep->put_lExecutionStatus(4);
pStep->put_lRelativePriority(3);
pStep->put_szDescription(L"转换数据任务");
pStep->put_szScriptLanguage(L"VBScript");
pStep->put_szStepName(L"DTSStep_DTSDataPumpTask");
pStep->put_szTaskName(L"DTSTask_DTSDataPumpTask");
pPack->GetDTSStep2((IDispatch *)&objSteps, pStep, &obj);
objSteps.Add(obj); Tasks objTasks(objpak2.GetTasks());
pTask->put_bAllowIdentityInserts(FALSE);
pTask->put_bUseFastLoad(TRUE);
pTask->put_lDataPumpOptions(0);
pTask->put_lDestinationConnectionID(2);
pTask->put_lExceptionFileOptions(1);
pTask->put_lFastLoadOptions(2);
pTask->put_lFetchBufferSize(1);
pTask->put_lInsertCommitSize(0);
pTask->put_lMaximumErrorCount(0);
pTask->put_lProgressRowCount(1000);
pTask->put_lSourceConnectionID(1);
pTask->put_szDataPumpTaskName(L"DTSTask_DTSDataPumpTask");
pTask->put_szDescription(L"转换数据任务");
pTask->put_szDestinationObjectName(L"[pubs].[dbo].[test041210]");
pTask->put_szExceptionFileColumnDelimiter(L"\t");
pTask->put_szExceptionFileName(L"c:\\ddd.txt");
pTask->put_szExceptionFileRowDelimiter(L"\r\n");
pTask->put_szExceptionFileTextQualifier(L"\"");
pTask->put_szSourceObjectName(L"C:\\bbb.txt");
pTask->put_varFirstRow(_variant_t("0"));
pTask->put_varLastRow(_variant_t("0"));
IDispatch* objDataPumpTask = NULL;
pPack->GetDTSDataPumpTask2((IDispatch *)objTasks, pTask, &objDataPumpTask);

IDispatch* objTrans = NULL;
pPack->GetDTSTransformations((IDispatch *)pTask, &objTrans);
// Transformations objTrans = (Transformations)obj;
pTran->put_bForceBlobsInMemory(FALSE);
pTran->put_lForceSourceBlobsBuffered(0);
pTran->put_lInMemoryBlobSize(1048576);
pTran->put_lTransformFlags(63);
pTran->put_lTransformPhases(4);
pTran->put_szTransformation2Name(L"DTSTransformation");
IDispatch* objTran = NULL;
pPack->GetDTSTransformation2(objTrans, pTran, &objTran); IDispatch* objCol1s = NULL;
pPack->GetDTSSourceColumns(objTran, &objCol1s);
Columns objSourceColumns = (Columns)objCol1s;
pCol1->put_bNullable(TRUE);
pCol1->put_lDataType(130);
pCol1->put_lFlags(32);
pCol1->put_lNumericScale(0);
pCol1->put_lOrdinal(1);
pCol1->put_lPrecision(0);
pCol1->put_lSize(11);
pCol1->put_szColumnName(L"Col001");
IDispatch* objCol1 = NULL;
pPack->GetDTSSourceColumn(objCol1s, pCol1, &objCol1);
objSourceColumns.Add(objCol1); IDispatch* objCols2 = NULL;
pPack->GetDTSDestinationColumns(objTran, &objCols2);
Columns objDestColumns = (Columns)objCols2;
pCol2->put_bNullable(TRUE);
pCol2->put_lDataType(129);
pCol2->put_lFlags(24);
pCol2->put_lNumericScale(0);
pCol2->put_lOrdinal(1);
pCol2->put_lPrecision(0);
pCol2->put_lSize(11);
pCol2->put_szColumnName(L"Mobile");
IDispatch* objCol2 = NULL;
pPack->GetDestinationColumn(objCols2, pCol2, &objCol2);
objSourceColumns.Add(objCol2); int nRet;
pPack->ExecutePackage2((IDispatch *)&objpak2, (IDispatch *)&objTasks, objDataPumpTask, objTrans, objTran,&nRet);
}

Answer 2

提示的错误是：
0xC0000005: Access Violation

Answer 3

你在返回之前没有AddRef,局部变量超出作用域的时候把对象释放了

Answer 4

非常感谢 jiangsheng(蒋晟.MSMVP2004Jan)，我在将一个类的对象作为一个接口方法的输出参数（返回值）时，是调用了调用了该对象的QueryInterface方法来实现的，这样我在调用该接口方法时就可以正确的返回对象了，即（上面的第一个接口方法改为，只改了一行，请看注释）：
[id(22), helpstring("设计DTS包类的属性")] HRESULT GetDTSPackage2([out, retval]IDispatch **pPackage2);STDMETHODIMP CDTSPackage2::GetDTSPackage2(IDispatch **pPackage2)
{
AFX_MANAGE_STATE(AfxGetStaticModuleState()) CoInitialize(NULL);
_Package2 objPackage2;
if (!objPackage2.CreateDispatch("DTS.Package2"))
{
m_dwErrorNumber = ERROR_PACKAGE2CREATEDISPATCH;
*pPackage2 = NULL;
return S_OK;
} try
{
objPackage2.SetName(m_dtsPackage2.szPackageName);
objPackage2.SetWriteCompletionStatusToNTEventLog(m_dtsPackage2.bWriteCompletionStatusToNTEventLog);
objPackage2.SetFailOnError(m_dtsPackage2.bFailOnError);
objPackage2.SetPackagePriorityClass(m_dtsPackage2.lPackagePriorityClass);
objPackage2.SetMaxConcurrentSteps(m_dtsPackage2.lMaxConcurrentSteps);
objPackage2.SetLineageOptions(m_dtsPackage2.lLineageOptions);
objPackage2.SetUseTransaction(m_dtsPackage2.bUseTransaction);
objPackage2.SetTransactionIsolationLevel(m_dtsPackage2.lTransactionIsolationLevel);
objPackage2.SetAutoCommitTransaction(m_dtsPackage2.bAutoCommitTransaction);
objPackage2.SetRepositoryMetadataOptions(m_dtsPackage2.lRepositoryMetadataOptions);
objPackage2.SetUseOLEDBServiceComponents(m_dtsPackage2.bUseOLEDBServiceComponents);
objPackage2.SetLogToSQLServer(m_dtsPackage2.bLogToSQLServer);
objPackage2.SetLogServerFlags(m_dtsPackage2.lLogServerFlags);
objPackage2.SetFailPackageOnLogFailure(m_dtsPackage2.bFailPackageOnLogFailure);
objPackage2.SetExplicitGlobalVariables(m_dtsPackage2.bExplicitGlobalVariables);
objPackage2.SetPackageType(m_dtsPackage2.lPackageType);
////////////////////
objPackage2.SetDescription(m_dtsPackage2.szDescription);
objPackage2.SetLogFileName(m_dtsPackage2.szLogFileName);
objPackage2.SetLogServerName(m_dtsPackage2.szLogServerName);
objPackage2.SetLogServerPassword(m_dtsPackage2.szLogServerPassword);
objPackage2.SetLogServerUserName(m_dtsPackage2.szLogServerPassword);
}
catch (_com_error &e)
{
*pPackage2 = NULL;
PrintComError(e);
m_dwErrorNumber = ERROR_PACKAGE2CREATEDISPATCH;
return S_OK;
} m_dwErrorNumber = 0;
//*pPackage2 = objPackage2;
         objPackage2.m_lpDispatch->QueryInterface(IID_IDispatch, (void **)pPackage2);    //将上面一行替换成该行
memset(&m_dtsPackage2, 0, sizeof(m_dtsPackage2));
return S_OK;
}
但是，在我的第二个回复中提到的函数pPack->ExecutePackage2((IDispatch *)&objpak2, (IDispatch *)&objTasks, objDataPumpTask, objTrans, objTran,&nRet)的最后一句还是出现了同样的错误，不知是何原因，下面放出该函数的代码。

Answer 5

HRESULT ExecutePackage2([in]IDispatch** pDTSPackage2, [in]IDispatch** pDTSTasks, [in]IDispatch** pDTSTask, [in]IDispatch** pDTSTransformations, [in]IDispatch** pDTSTransformation2, [out,retval]int *pRet);STDMETHODIMP CDTSPackage2::ExecutePackage2(IDispatch** pDTSPackage2, IDispatch** pDTSTasks, IDispatch** pDTSTask, IDispatch** pDTSTransformations, IDispatch** pDTSTransformation2, int *pRet)
{
AFX_MANAGE_STATE(AfxGetStaticModuleState()) _Package2 objPak;
objPak.AttachDispatch(*pDTSPackage2);
Tasks objTasks;
objTasks.AttachDispatch(*pDTSTasks);
Task objTask;
objTask.AttachDispatch(*pDTSTask);
Transformations objTrans;
objTrans.AttachDispatch(*pDTSTransformations);
Transformation2 objTran;
objTran.AttachDispatch(*pDTSTransformation2); try
{
objTrans.Add(objTran);
objTasks.Add(objTask); szTemp = objPak.GetName();　　//可以正常的通过该方法获得该对象的一个属性 objPak.Execute();　　　　　　//该行出现了跟前面所说的同样的错误0xC0000005: Access Violation，不知是不是这个方法要使用的其他的对象不可用，很郁闷。 }
catch (_com_error &e)
{
if (objTran != NULL)
{
objTran.ReleaseDispatch();
objTran = NULL;
}
if (objTrans != NULL)
{
objTrans.ReleaseDispatch();
objTrans = NULL;
}
if (objTasks != NULL)
{
objTasks.ReleaseDispatch();
objTasks = NULL;
}
if (objTask != NULL)
{
objTask.ReleaseDispatch();
objTask = NULL;
} PrintComError(e);
*pRet = m_dwErrorNumber = ERROR_EXECUTEPACKAGE2;
return S_OK;
} *pRet = m_dwErrorNumber = 0;
return S_OK;
}我的COM主要实现的是DTS，调用SQLSERVER提供的dtspack.dll来实现的。请求各位大侠指点。
思归、孟子E章、天下、各位大侠快来帮忙呀！感激不尽！

Answer 6

jiangsheng(蒋晟.MSMVP2004Jan)
说的没有错啊。
_Package2 objPackage2;这是个局部变量啊。怎么可以这么分配呢。

Answer 7

hjunxu(hjun)的意思是我应该怎么做呢？

Answer 8

_Package2 objPackage2;
这样声明一个类的变量有问题吗？
我在将这个对象传出时调用objPackage2.m_lpDispatch->QueryInterface(IID_IDispatch, (void **)pPackage2); 我认为，这行代码实现了将对象objPackage2传出，该方法就使接口的计数器加1，所以我可以在其他接口函数中使用该对象了，是不是这样的呢？

Answer 9

IDispatch *patch;//或者你自己定义的接口指针和响应的IID
bjPackage2.m_lpDispatch->QueryInterface(IID_IDispatch, (void **)&patch);

Answer 10

不明白seman(西曼) 说得是什么意思，我现在好像就是这样做的呀？

Answer 11

我只是一时兴致，没有看楼主的问题，只是简单的推荐一下而已，楼主有兴趣可以看下下面的文章
http://dev.csdn.net/article/27/27324.shtm
（如果文不对题就算了）