结合ADO、ADOX和MFC的文档/视图/框架架构创建和打开Access数据库

本文描述了如何在MFC的文档/视图/框架架构中使用ADO和ADOX来创建和打开数据库。 预备阅读 MFC技术文章 TN025: Document, View, and Frame Creation 微软知识库文章 Q183606 ActiveX Data Objects (ADO) Frequently Asked Questions Q169496 INFO: Using Acti

本文描述了如何在MFC的文档/视图/框架架构中使用ADO和ADOX来创建和打开数据库。

预备阅读

MFC技术文章

• TN025: Document, View, and Frame Creation

微软知识库文章

• Q183606 ActiveX Data Objects (ADO) Frequently Asked Questions
• Q169496 INFO: Using ActiveX Data Objects (ADO) via #import in VC++
• Q317881 HOW TO: Create an Access Database Using ADOX and Visual C# .NET
• Q252908 HOWTO: Create a Table with Primary Key Through ADOX
• Q201826 PRB: Error 3265 When You Access Properties Collection

Office VBA参考

• Creating and Modifying Access Tables

步骤

1. 在计算机上安装MDAC2.5以上版本
2. 打开VC。首先，我们使用MFC应用程序向导创建一个标准的MDI程序，这里我为这个工程起名为Passport,然后在stdafx.h中导入ADOX
   #include
   #import "c:/Program Files/Common Files/system/ado/Msado15.dll" rename("EOF","adoEOF") rename("DataTypeEnum","adoDataTypeEnum")
   #import "c:/Program Files/Common Files/System/ADO/Msadox.dll" rename("EOF", "adoXEOF") rename("DataTypeEnum","adoXDataTypeEnum")
   #import "c:/PROGRAM FILES/COMMON FILES/System/ado/MSJRO.DLL"
   
   根据你的计算机上ADO的安装路径，这里的路径可能有所不同。
3. 在文档类中声明数据库连接 ADODB::_ConnectionPtr m_pConn;和记录集 ADODB::_RecordsetPtr m_pSet;，并且重载文档类的DeleteContents() 、OnNewDocument()和OnOpenDocument()函数，用于断开数据库连接，创建数据库和表，以及打开现有的数据库。
   （作者的抱怨：CSDN文章中心该改改了，代码排版这么麻烦）
   void CPassportDoc::DeleteContents()
   {
   try
   {
   if(m_pSet){
   ESRecordsetClose(m_pSet);
   }
   if(m_pConn)
   if(m_pConn->State&ADODB::adStateOpen)
   m_pConn->Close();
   m_pConn=NULL;
   }
   catch(_com_error &e){
   ESErrPrintProviderError(m_pConn);
   ESErrPrintComError(e);
   }
   CDocument::DeleteContents();
   }BOOL CPassportDoc::OnNewDocument()
   {
   if (!CDocument::OnNewDocument())
   return FALSE;
   CFileDialog dlgFile(FALSE, _T(".mdb"), NULL, OFN_HIDEREADONLY | OFN_PATHMUSTEXIST, _T("Access 数据库 (*.mdb)|*.mdb|全部文件(*.*)|*.*||"));
   if (dlgFile.DoModal() != IDOK)
   return FALSE;
   CString strDBPath=dlgFile.GetPathName();
   if(!CreateDB(strDBPath))return FALSE;
   //create
   CString strConnect;
   
   strConnect.Format(_T("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=%s"),strDBPath);
   COleVariant Connect(strConnect);
   // TODO: add reinitialization code here
   // (SDI documents will reuse this document)
   try{
   m_pConn.CreateInstance(_T("ADODB.Connection"));
   m_pSet.CreateInstance(_T("ADODB.Recordset"));
   m_pConn->PutCommandTimeout(30);
   m_pConn->PutConnectionTimeout(30);
   m_pConn->put_CursorLocation(ADODB::adUseClient);
   m_pConn->Open(_bstr_t(strConnect),_bstr_t(),_bstr_t(),ADODB::adConnectUnspecified);
   ::ESRecordsetOpen(_T("Passport"),m_pConn,m_pSet);
   SetPathName(strDBPath);
   return TRUE;
   }
   catch(_com_error &e){
   ESErrPrintProviderError(m_pConn);
   ESErrPrintComError(e);
   }
   catch(...){
   }
   m_pConn=NULL;
   return FALSE;
   }
   BOOL CPassportDoc::OnOpenDocument(LPCTSTR lpszPathName)
   {
   if (!CDocument::OnOpenDocument(lpszPathName))
   return FALSE;
   ADODB::_ConnectionPtr tempConnn;
   CString strConnect;
   CString strDBPath=lpszPathName;
   strConnect.Format(_T("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=%s"),strDBPath);
   COleVariant Connect(strConnect);
   // TODO: add reinitialization code here
   // (SDI documents will reuse this document)
   try{
   tempConnn.CreateInstance(_T("ADODB.Connection"));
   tempConnn->PutCommandTimeout(30);
   tempConnn->PutConnectionTimeout(30);
   tempConnn->put_CursorLocation(ADODB::adUseClient);
   tempConnn->Open(_bstr_t(strConnect),_bstr_t(),_bstr_t(),ADODB::adConnectUnspecified);
   SetPathName(strDBPath);
   m_pConn=tempConnn;
   m_pSet=NULL;
   m_pSet.CreateInstance(_T("ADODB.Recordset"));
   ::ESRecordsetOpen(_T("Passport"),m_pConn,m_pSet);
   UpdateAllViews(NULL,UpdateHintRefresh);
   return TRUE;
   }
   catch(_com_error &e){
   ESErrPrintProviderError(tempConnn);
   ESErrPrintComError(e);
   }
   catch(...){
   }
   return FALSE;
   }
   
4. 编写一个辅助函数，用于创建数据库、表和索引
   BOOL CPassportDoc::CreateDB(LPCTSTR lpszFile)
   {
   if(::PathFileExists(lpszFile)){
   CString strTemp;
   strTemp.Format(IDS_TARGET_EXISTS,lpszFile);
   AfxMessageBox(lpszFile);
   return FALSE;
   }
   ADODB::_ConnectionPtr tempConnn;
   ADOX::_CatalogPtr pCatalog = NULL;
   ADOX::_TablePtr pTable = NULL;
   ADOX::_IndexPtr pIndexNew = NULL;
   ADOX::_IndexPtr pIndex = NULL;
   CString strConnect;
   CString strDBPath=lpszFile;
   strConnect.Format(_T("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=%s"),strDBPath);
   COleVariant Connect(strConnect);
   try{
   pCatalog.CreateInstance(_T("ADOX.Catalog"));
   pCatalog->Create((LPCTSTR)strConnect);//创建数据库
   tempConnn.CreateInstance(_T("ADODB.Connection"));
   tempConnn->PutCommandTimeout(30);
   tempConnn->PutConnectionTimeout(30);
   tempConnn->put_CursorLocation(ADODB::adUseClient);
   tempConnn->Open(_bstr_t(strConnect),_bstr_t(),_bstr_t(),ADODB::adConnectUnspecified);
   pCatalog->PutActiveConnection(_variant_t((IDispatch *) tempConnn));
   pTable.CreateInstance(_T("ADOX.Table"));
   pTable->ParentCatalog =pCatalog;
   pTable->Name="Passport";
   ADOX::ColumnsPtr pCols =pTable->Columns;
   pCols->Append(_T("RecordID") ,ADOX::adInteger,0);//自动编号字段
   pCols->Append(_T("Name") ,ADOX::adWChar,255);//文本字段
   pCols->Append(_T("DateOfBirth") ,ADOX::adDate,0);//日期字段
   pCols->Append(_T("OtherInfo"),ADOX::adLongVarWChar,0);//备注字段
   pCatalog->Tables->Refresh();
   long lCount=pCols->Count;
   for(long i=0;i pCols->GetItem(i)->ParentCatalog =pCatalog;//重要！设置Catalog,参见Q201826 PRB: Error 3265 When You Access Properties Collection
   ADOX::PropertiesPtr pProperties=pCols->GetItem(i)->Properties;
   if(pProperties){//这里是用于调试的属性显示代码
   long lp=pProperties->Count;
   TRACE("Properties for Col %s/r/n",(LPCTSTR)pCols->GetItem(i)->Name);
   for(long j=0;j TRACE("/rProperty %s:%s/r/n",g_GetValueString(pProperties->GetItem(j)->Name)
   ,g_GetValueString(pProperties->GetItem(j)->Value));
   }
   }
   }
   pCols->GetItem(_T("RecordID"))->Properties->GetItem(_T("Description"))->Value=_T("记录编号");//注释
   pCols->GetItem(_T("RecordID"))->Properties->GetItem(_T("AutoIncrement"))->Value=true;//自动编号
   pCols->GetItem(_T("Name"))->Properties->GetItem(_T("Jet OLEDB:Compressed UniCode Strings"))->Value=true;
   pCols->GetItem(_T("Name"))->Properties->GetItem(_T("Description"))->Value=_T("姓名");
   pCols->GetItem(_T("DateOfBirth"))->Properties->GetItem(_T("Description"))->Value=_T("出生日期");
   pCols->GetItem(_T("OtherInfo"))->Properties->GetItem(_T("Jet OLEDB:Compressed UniCode Strings"))->Value=true;
   pCols->GetItem(_T("OtherInfo"))->Properties->GetItem(_T("Description"))->Value=_T("其他信息");
   pCatalog->Tables->Append(_variant_t ((IDispatch*)pTable));//添加表
   pCatalog->Tables->Refresh();//刷新
   pIndexNew.CreateInstance(_T("ADOX.Index"));
   pIndexNew->Name = "RecordID";//索引名称
   pIndexNew->Columns->Append("RecordID",ADOX::adInteger,0);//索引字段
   pIndexNew->PutPrimaryKey(-1);//主索引
   pIndexNew->PutUnique(-1);//唯一索引
   pTable->Indexes->Append(_variant_t ((IDispatch*)pIndexNew));//创建索引
   pIndexNew=NULL;
   pCatalog->Tables->Refresh();//刷新
   return TRUE;
   }
   catch(_com_error &e){
   ESErrPrintProviderError(tempConnn);
   ESErrPrintComError(e);
   return FALSE;
   }
   catch(...){
   }
   return FALSE;
   }
5. 辅助的数据库函数。由于这些函数是Jiangsheng以前为一个项目写的。所以命名有些奇怪。借鉴了MFC类CDaoRecordset的部分代码
   #define _countof(array) (sizeof(array)/sizeof(array[0]))
   BOOL ESRecordsetOpen(
   LPCTSTR lpszSQL
   ,ADODB::_ConnectionPtr pConnection
   ,ADODB::_RecordsetPtr& rst
   ,ADODB::CursorTypeEnum CursorType//=adOpenDynamic
   ,ADODB::LockTypeEnum LockType//=ado20::adLockOptimistic
   ,long lOptions//=adCmdUnspecified
   )
   {
   _bstr_t bstrQuery;
   const TCHAR _afxParameters2[] = _T("PARAMETERS ");
   const TCHAR _afxSelect2[] = _T("SELECT ");
   const TCHAR _afxTransform2[] = _T("TRANSFORM ");
   const TCHAR _afxTable2[] = _T("TABLE ");
   // construct the default query string
   if ((_tcsnicmp(lpszSQL, _afxSelect2, _countof(_afxSelect2)-1) != 0) &&
   (_tcsnicmp(lpszSQL, _afxParameters2, _countof(_afxParameters2)-1) != 0) &&
   (_tcsnicmp(lpszSQL, _afxTransform2, _countof(_afxTransform2)-1) != 0) &&
   (_tcsnicmp(lpszSQL, _afxTable2, _countof(_afxTable2)-1) != 0)){
   CString strTemp;
   strTemp.Format("SELECT * FROM (%s)",lpszSQL);
   bstrQuery=(LPCTSTR)strTemp;
   }
   else
   bstrQuery=lpszSQL;
   if(rst!=NULL){
   rst->CursorLocation=ADODB::adUseClient;
   rst->Open(bstrQuery,_variant_t(pConnection.GetInterfacePtr(),true),CursorType,LockType,lOptions);
   }
   TRACE("Open Recordset:%s/n",lpszSQL);
   return ESRecordsetIsOpen(rst);
   }
   BOOL ESRecordsetIsOpen(const ADODB::_RecordsetPtr& rst)
   {
   if(rst!=NULL){
   return rst->State&ADODB::adStateOpen;
   }
   return FALSE;
   }
   void ESRecordsetClose(ADODB::_RecordsetPtr& rst)
   {
   if(rst!=NULL){
   if(rst->State&ADODB::adStateOpen)
   rst->Close();
   }
   }
   CString g_GetValueString(const _variant_t& val)
   {
   CString strVal;
   _variant_t varDest(val);
   if(!g_varIsValid(val)){
   return strVal;
   }
   if(val.vt==VT_BOOL){
   if(val.boolVal==VARIANT_FALSE){
   return _T("否");
   }
   else
   return _T("是");
   }
   else{
   }
   if(varDest.vt!=VT_BSTR){
   HRESULT hr=::VariantChangeType(&varDest,&varDest,VARIANT_NOUSEROVERRIDE|VARIANT_LOCALBOOL,VT_BSTR);
   if(FAILED(hr)){
   return strVal;
   }
   
   }
   strVal=(LPCTSTR)_bstr_t(varDest);
   return strVal;
   }
6. 错误处理代码
   void ESErrPrintComError(_com_error &e)
   {
   _bstr_t bstrSource(e.Source());
   _bstr_t bstrDescription(e.Description());
   CString strTemp;
   strTemp.Format(_T("´错误/n/t错误代码: %08lx/n/t含义: %s/n/t来自 : %s/n/t描述 : %s/n"),
   e.Error(),e.ErrorMessage(),(LPCSTR) bstrSource,(LPCSTR) bstrDescription);
   // Print COM errors.
   ::AfxMessageBox(strTemp);
   #ifdef _DEBUG
   AfxDebugBreak();
   #endif
   }
   void ESErrPrintProviderError(ADODB::_ConnectionPtr pConnection)
   {
   if(pConnection==NULL) return;
   try{
   // Print Provider Errors from Connection object.
   // pErr is a record object in the Connection's Error collection.
   ADODB::ErrorPtr pErr = NULL;
   ADODB::ErrorsPtr pErrors=pConnection->Errors;
   if(pErrors){
   if( (pErrors->Count) > 0){
   long nCount = pErrors->Count;
   // Collection ranges from 0 to nCount -1.
   for(long i = 0;i < nCount;i++){
   pErr = pErrors->GetItem(i);
   CString strTemp;
   strTemp.Format(_T("/t 错误代码: %x/t%s"), pErr->Number, pErr->Description);
   }
   }
   }
   }
   catch(_com_error &e){
   ESErrPrintComError(e);
   }
   }

总结

在文档/视图/框架架构中集成数据库访问总体来说还是难度不大的。微软提供了很多示例的代码，大部分工作只是把示例代码从其他语言改写到VC。主要的工作是对MFC的文档/视图/框架架构的理解，在适当的时候调用这些代码。

尽管我在打开数据库的同时也打开了一个记录集，但是我并未给出显示记录集内容的代码，这超出了本文的范围。我可以给出的提示是使用现成的数据列表控件来显示，微软知识库文章Q229029 SAMPLE: AdoDataGrid.exe Demonstrates How to Use ADO with DataGrid Control Using Visual C++可以作为参考。