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
在阅读本文之前，建议先对COM，数据库和MFC的文档/视图/框架有一个基本的了解。推荐阅读下列文章
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
在计算机上安装MDAC2.5以上版本
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 <shlwapi.h>
#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。
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;
}
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<lCount;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<lp;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;
}
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;
}
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。
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