Save 및 Open 메서드 예제(VC++)

아티클
05/30/2023

다음 세 가지 예제에서는 Save 및 Open 메서드를 함께 사용하는 방법을 보여 줍니다.

출장 중에 데이터베이스의 테이블을 사용하려는 경우를 가정합니다. 출발하기 전에 레코드 집합으로 데이터에 액세스하고 전송 가능한 형식으로 저장합니다. 목적지에 도착하면 연결이 끊긴 로컬 레코드 집합으로 레코드 집합에 액세스합니다. 레코드 집합을 변경한 다음, 다시 저장합니다. 마지막으로, 집으로 돌아오면 데이터베이스에 다시 연결하여 이동 중에 변경한 내용으로 업데이트합니다.

// BeginSaveCpp.cpp  
// compile with: /EHsc  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  
  
#include <ole2.h>  
#include <stdio.h>  
#include <conio.h>  
#include <io.h>  
  
// Function declarations  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
bool FileExists();  
void SaveX1();  
void SaveX2();  
void SaveX3();  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  
  
int main() {  
   if ( FAILED(::CoInitialize(NULL)) )  
      return -1;  
  
   // If File exists in the specified directory, then display error  
   if (!FileExists()) {  
      SaveX1();  
      SaveX2();  
      SaveX3();  
   }  
  
   ::CoUninitialize();  
}  
  
// First, access and save the authors table.  
void SaveX1() {  
   HRESULT hr = S_OK;  
  
   // Define ADO object pointers.  Initialize pointers on define.  
   // These are in the ADODB::  namespace.  
   _RecordsetPtr pRstAuthors = NULL;  
  
   // Definitions of other variables  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source' ; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   try {  
      TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));  
  
      pRstAuthors->Open("SELECT * FROM authors",strCnn, adOpenDynamic,   
         adLockBatchOptimistic, adCmdText);  
  
      // For sake of illustration, save the Recordset to a diskette in XML format.  
      pRstAuthors->Save("c:\\pubs.xml", adPersistXML);  
   }  
   catch(_com_error &e) {  
      // Notify the user of errors, if any.  
      // Pass a connection pointer accessed from the Recordset.  
      _variant_t vtConnect = pRstAuthors->GetActiveConnection();  
  
      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      switch(vtConnect.vt) {  
      case VT_BSTR:  
         PrintComError(e);  
         break;  
      case VT_DISPATCH:  
         PrintProviderError(vtConnect);  
         break;  
      default:  
         printf("Errors occurred.");  
         break;  
      }  
   }  
  
   if (pRstAuthors)  
      if (pRstAuthors->State == adStateOpen)  
         pRstAuthors->Close();  
}  
  
// At this point, you have arrived at your destination.  
// You will access the authors table as a local, disconnected Recordset.   
// Don't forget you must have the MSPersist provider on the machine you   
// are using in order to access the saved file, c:\pubs.xml.  
void SaveX2() {  
   HRESULT hr = S_OK;  
  
   // Define ADO object pointers.  Initialize pointers on define.  
   // These are in the ADODB::  namespace.  
   _RecordsetPtr pRstAuthors = NULL;  
  
   try {  
      TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));  
  
      // For sake of illustration, we specify all parameters.  
      pRstAuthors->Open("c:\\pubs.xml", "Provider='MSPersist';", adOpenForwardOnly, adLockBatchOptimistic, adCmdFile);  
  
      // Now you have a local, disconnected Recordset.  
      // (In this example, changes will not be saved).  
      pRstAuthors->Find("au_lname = 'Carson'", NULL, adSearchForward);  
      if (pRstAuthors->EndOfFile) {  
         printf("Name not found ...\n");  
         pRstAuthors->Close();  
         return;  
      }  
      pRstAuthors->GetFields()->GetItem("City")->PutValue("Chicago");  
      pRstAuthors->Update();  
  
      // Save changes in ADTG format this time, purely for sake of  illustration.   
      // Note that the previous version is still on the diskette as c:\pubs.xml.  
      pRstAuthors->Save("c:\\pubs.adtg", adPersistADTG);  
   }  
   catch(_com_error &e){  
      // Notify the user of errors if any.  
      // Pass a connection pointer accessed from the Recordset.  
      _variant_t vtConnect = pRstAuthors->GetActiveConnection();  
  
      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      switch(vtConnect.vt) {  
      case VT_BSTR:  
         PrintComError(e);  
         break;  
      case VT_DISPATCH:  
         PrintProviderError(vtConnect);  
         break;  
      default:  
         printf("Errors occurred.");  
         break;  
      }  
   }  
  
   if (pRstAuthors)  
      if (pRstAuthors->State == adStateOpen)  
         pRstAuthors->Close();  
}  
  
// Now update the database with changes.  
void SaveX3() {  
   HRESULT hr = S_OK;  
  
   // Define ADO object pointers.  Initialize pointers on define.  
   // These are in the ADODB::  namespace.  
   _RecordsetPtr pRstAuthors = NULL;  
   _ConnectionPtr pCnn = NULL;  
  
   // Definitions of other variables  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   try {  
      TESTHR(pCnn.CreateInstance(__uuidof(Connection)));  
  
      TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));  
  
      // If there is no ActiveConnection, you can open with defaults.  
      pRstAuthors->Open("c:\\pubs.adtg", "Provider=MSPersist;",  
         adOpenForwardOnly, adLockBatchOptimistic, adCmdFile);  
  
      // Connect to the database, associate the Recordset with the connection,   
      // then update the database table with the changed Recordset.  
      pCnn->Open(strCnn, "", "", NULL);  
  
      pRstAuthors->PutActiveConnection(_variant_t((IDispatch *) pCnn));  
      pRstAuthors->UpdateBatch(adAffectAll);  
   }  
   catch(_com_error &e) {  
      // Notify the user of errors if any.  
      // Pass a connection pointer accessed from the Recordset.  
      _variant_t vtConnect = pRstAuthors->GetActiveConnection();  
  
      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      switch(vtConnect.vt) {  
      case VT_BSTR:  
         PrintComError(e);  
         break;  
      case VT_DISPATCH:  
         PrintProviderError(vtConnect);  
         break;  
      default:  
         printf("Errors occurred.");  
         break;  
      }  
   }  
  
   if (pRstAuthors)  
      if (pRstAuthors->State == adStateOpen)  
         pRstAuthors->Close();  
   if (pCnn)  
      if (pCnn->State == adStateOpen)  
         pCnn->Close();  
}  
  
void PrintProviderError(_ConnectionPtr pConnection) {  
   // Print Provider Errors from Connection object.  
   // pErr is a record object in the Connection's Error collection.  
   ErrorPtr pErr = NULL;  
  
   if ( (pConnection->Errors->Count) > 0) {  
      long nCount = pConnection->Errors->Count;  
  
      // Collection ranges from 0 to nCount -1.  
      for ( long i = 0 ; i < nCount ; i++) {  
         pErr = pConnection->Errors->GetItem(i);  
         printf("Error number: %x\t%s\n", pErr->Number, (LPCSTR) pErr->Description);  
      }  
   }  
}  
  
void PrintComError(_com_error &e) {  
   _bstr_t bstrSource(e.Source());  
   _bstr_t bstrDescription(e.Description());  
  
   // Print COM errors.   
   printf("Error\n");  
   printf("\tCode = %08lx\n", e.Error());  
   printf("\tCode meaning = %s\n", e.ErrorMessage());  
   printf("\tSource = %s\n", (LPCSTR) bstrSource);  
   printf("\tDescription = %s\n", (LPCSTR) bstrDescription);  
}  
  
bool FileExists() {  
   struct _finddata_t xml_file;  
   long hFile;  
  
   if( (hFile = _findfirst("c:\\pubs.xml", &xml_file )) != -1L)  
   {  
      printf( "File already exists!\n" );  
      return(true);  
   }  
   else  
      return (false);  
}

참고 항목

Open 메서드(ADO 레코드 집합)
레코드 집합 개체(ADO)
Save 메서드

다음을 통해 공유

Save 및 Open 메서드 예제(VC++)

참고 항목

피드백

추가 리소스