VCADO连接类用于连接数据库资源-CSDN文库

共2个文件

h：1个

cpp：1个

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在IT领域，数据库连接是应用程序与数据库交互的基础。在Windows编程中，Visual C++（简称VC）经常被用来开发各种应用程序，而ActiveX Data Objects（简称ADO）是Microsoft提供的一种高效、轻量级的数据库访问技术。本篇文章将深入探讨如何在VC中使用ADO连接类来连接数据库。 ADO是OLE DB的一部分，它为开发者提供了一种简单的方式来访问和操作数据源，包括SQL Server、Access、Oracle等。ADO连接类主要涉及以下知识点： 1. **ADO对象模型**：ADO的核心对象包括Connection、Command、Recordset、Parameter和Error。Connection对象负责建立和管理到数据源的连接，Command对象用于执行数据库命令，Recordset对象则用于存储查询结果，Parameter对象用于传递参数化查询的参数，Error对象用于处理可能出现的错误信息。 2. **连接字符串**：在VC中，使用ADO连接数据库首先需要创建一个Connection对象，并通过ConnectionString属性设置连接字符串。连接字符串通常包含数据库类型、服务器名称、数据库名称、用户名和密码等信息。例如，对于SQL Server，连接字符串可能如下所示： ``` "Provider=SQLOLEDB;Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;" ``` 3. **打开和关闭连接**：使用`Open()`方法打开数据库连接，完成操作后调用`Close()`方法关闭连接。例如： ```cpp CoInitialize(NULL); _ConnectionPtr conn("ADODB.Connection"); conn->ConnectionString = "your_connection_string"; conn->Open(); // 数据库操作 conn->Close(); CoUninitialize(); ``` 4. **执行SQL命令**：通过Command对象的`Execute()`方法执行SQL命令，可以是SELECT、INSERT、UPDATE或DELETE语句。如果查询返回结果，可以获取Recordset对象。例如： ```cpp _CommandPtr cmd("ADODB.Command"); cmd->ActiveConnection = conn; cmd->CommandText = "SELECT * FROM TableName"; _RecordsetPtr rs = cmd->Execute(NULL, NULL, adCmdText); ``` 5. **遍历Recordset**：Recordset对象提供了遍历查询结果的方法，如`MoveFirst()`, `MoveNext()`, `IsEOF()`等。可以通过这些方法获取并处理数据。例如： ```cpp while (!rs->IsEOF) { // 访问字段值，如rs->Fields["FieldName"]->Value rs->MoveNext(); } ``` 6. **事务处理**：当需要执行一系列数据库操作并确保它们要么全部成功要么全部回滚时，可以使用Connection对象的`BeginTrans()`, `CommitTrans()`, `RollbackTrans()`方法进行事务控制。 7. **错误处理**：ADO提供了内置的错误处理机制，当发生错误时，可以通过Error对象获取错误信息。 8. **释放资源**：在程序结束时，确保所有打开的对象都被正确释放，以避免内存泄漏。在C++中，可以使用智能指针（如 `_com_ptr_t`）自动管理COM对象的生命周期。 VC中使用ADO连接类进行数据库操作，不仅简化了代码，还提高了效率。通过理解ADO对象模型，正确设置连接字符串，以及熟练掌握执行SQL命令、遍历记录集、事务处理和错误处理等方法，开发者可以构建稳定且高效的数据库应用程序。

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ADO连接类.rar （2个子文件）

ADO连接类

adoDatabase.h 17KB

adoDatabase.cpp 48KB

#include "stdafx.h" #include "adoDatabase.h" #define ChunkSize 100 BOOL CJetEngine::CCompactDatabase(CString strDatabaseSource, CString strDatabaseDestination) { try { ::CoInitialize(NULL); IJetEnginePtr jet(__uuidof(JetEngine)); HRESULT hr = jet->CompactDatabase(_bstr_t(strDatabaseSource.GetBuffer(0)), _bstr_t(strDatabaseDestination.GetBuffer(0))); ::CoUninitialize(); return hr == S_OK; } catch(_com_error & e) { ::CoUninitialize(); return FALSE; } } /////////////////////////////////////////////////////// // // CADODatabase Class // DWORD CADODatabase::GetRecordCount(_RecordsetPtr m_pRs) { DWORD numRows = 0; numRows = m_pRs->GetRecordCount(); if(numRows == -1) { if(m_pRs->EndOfFile != VARIANT_TRUE) m_pRs->MoveFirst(); while(m_pRs->EndOfFile != VARIANT_TRUE) { numRows++; m_pRs->MoveNext(); } if(numRows > 0) m_pRs->MoveFirst(); } return numRows; } BOOL CADODatabase::Open(LPCTSTR lpstrConnection, LPCTSTR lpstrUserID, LPCTSTR lpstrPassword) { HRESULT hr = S_OK; if(IsOpen()) Close(); if(strcmp(lpstrConnection, _T("")) != 0) m_strConnection = lpstrConnection; ASSERT(!m_strConnection.IsEmpty()); try { if(m_nConnectionTimeout != 0) m_pConnection->PutConnectionTimeout(m_nConnectionTimeout); // CString strUserID = lpstrUserID; CString strPassWord = lpstrPassword; BSTR connectionTemp = m_strConnection.AllocSysString(); BSTR userTemp = strUserID.AllocSysString(); BSTR pwdTemp = strPassWord.AllocSysString(); _bstr_t strConnect(connectionTemp,false); _bstr_t strUser(userTemp,false); _bstr_t strPwd(pwdTemp,false); hr = m_pConnection->Open(strConnect, strUser,strPwd, NULL); ::SysFreeString(connectionTemp); ::SysFreeString(userTemp); ::SysFreeString(pwdTemp); // //hr = m_pConnection->Open(_bstr_t(m_strConnection), _bstr_t(lpstrUserID), _bstr_t(lpstrPassword), NULL); return hr == S_OK; } catch(_com_error &e) { //dump_com_error(e); return FALSE; } } void CADODatabase::dump_com_error(_com_error &e) { CString ErrorStr; _bstr_t bstrSource(e.Source()); _bstr_t bstrDescription(e.Description()); ErrorStr.Format( "CADODataBase Error\n\tCode = %08lx\n\tCode meaning = %s\n\tSource = %s\n\tDescription = %s\n", e.Error(), e.ErrorMessage(), (LPCSTR)bstrSource, (LPCSTR)bstrDescription); m_strErrorDescription = (LPCSTR)bstrDescription ; m_strLastError = _T("Connection String = " + GetConnectionString() + '\n' + ErrorStr); m_dwLastError = e.Error(); #ifdef _DEBUG AfxMessageBox(ErrorStr, MB_OK | MB_ICONERROR ); #endif } BOOL CADODatabase::IsOpen() { if(m_pConnection ) return m_pConnection->GetState() != adStateClosed; return FALSE; } void CADODatabase::Close() { if(IsOpen()) m_pConnection->Close(); } /////////////////////////////////////////////////////// // // CADORecordset Class // CADORecordset::CADORecordset() { m_pRecordset = NULL; m_pCmd = NULL; m_strQuery = _T(""); m_strLastError = _T(""); m_dwLastError = 0; m_pRecBinding = NULL; m_pRecordset.CreateInstance(__uuidof(Recordset)); m_pCmd.CreateInstance(__uuidof(Command)); m_nEditStatus = CADORecordset::dbEditNone; m_nSearchDirection = CADORecordset::searchForward; } CADORecordset::CADORecordset(CADODatabase* pAdoDatabase) { m_pRecordset = NULL; m_pCmd = NULL; m_strQuery = _T(""); m_strLastError = _T(""); m_dwLastError = 0; m_pRecBinding = NULL; m_pRecordset.CreateInstance(__uuidof(Recordset)); m_pCmd.CreateInstance(__uuidof(Command)); m_nEditStatus = CADORecordset::dbEditNone; m_nSearchDirection = CADORecordset::searchForward; m_pConnection = pAdoDatabase->GetActiveConnection(); } BOOL CADORecordset::Open(_ConnectionPtr mpdb, LPCTSTR lpstrExec, int nOption) { Close(); if(strcmp(lpstrExec, _T("")) != 0) m_strQuery = lpstrExec; ASSERT(!m_strQuery.IsEmpty()); if(m_pConnection == NULL) m_pConnection = mpdb; m_strQuery.TrimLeft(); BOOL bIsSelect = m_strQuery.Mid(0, strlen("Select ")).CompareNoCase("select ") == 0 && nOption == openUnknown; try { m_pRecordset->CursorType = adOpenStatic; m_pRecordset->CursorLocation = adUseClient; if(bIsSelect || nOption == openQuery || nOption == openUnknown) m_pRecordset->Open((LPCSTR)m_strQuery, _variant_t((IDispatch*)mpdb, TRUE), adOpenStatic, adLockOptimistic, adCmdUnknown); else if(nOption == openTable) m_pRecordset->Open((LPCSTR)m_strQuery, _variant_t((IDispatch*)mpdb, TRUE), adOpenKeyset, adLockOptimistic, adCmdTable); else if(nOption == openStoredProc) { m_pCmd->ActiveConnection = mpdb; m_pCmd->CommandText = _bstr_t(m_strQuery); m_pCmd->CommandType = adCmdStoredProc; m_pConnection->CursorLocation = adUseClient; m_pRecordset = m_pCmd->Execute(NULL, NULL, adCmdText); } else { TRACE( "Unknown parameter. %d", nOption); return FALSE; } } catch(_com_error &e) { dump_com_error(e); return FALSE; } return m_pRecordset != NULL; } BOOL CADORecordset::Open(LPCTSTR lpstrExec, int nOption) { ASSERT(m_pConnection != NULL); ASSERT(m_pConnection->GetState() != adStateClosed); return Open(m_pConnection, lpstrExec, nOption); } BOOL CADORecordset::OpenSchema(int nSchema, LPCTSTR SchemaID) { try { _variant_t vtSchemaID = vtMissing; if(strlen(SchemaID) != 0) vtSchemaID = SchemaID; m_pRecordset = m_pConnection->OpenSchema((enum SchemaEnum)nSchema, vtMissing, vtSchemaID); return TRUE; } catch(_com_error &e) { dump_com_error(e); return FALSE; } } BOOL CADORecordset::Requery() { if(IsOpen()) { try { //m_pRecordset->Requery(adExecuteRecord); } catch(_com_error &e) { dump_com_error(e); return FALSE; } } return TRUE; } BOOL CADORecordset::GetFieldValue(LPCTSTR lpFieldName, double& dbValue) { double val = (double)NULL; _variant_t vtFld; try { vtFld = m_pRecordset->Fields->GetItem(lpFieldName)->Value; switch(vtFld.vt) { case VT_R4: val = vtFld.fltVal; break; case VT_R8: val = vtFld.dblVal; break; case VT_DECIMAL: //Corrected by Jos?Carlos Mart�nez Gal�n val = vtFld.decVal.Lo32; val *= (vtFld.decVal.sign == 128)? -1 : 1; val /= pow(10.0, vtFld.decVal.scale); break; case VT_UI1: val = vtFld.iVal; break; case VT_I2: case VT_I4: val = vtFld.lVal; break; case VT_INT: val = vtFld.intVal; break; case VT_NULL: case VT_EMPTY: val = 0; break; default: val = vtFld.dblVal; } dbValue = val; return TRUE; } catch(_com_error &e) { dump_com_error(e); return FALSE; } } BOOL CADORecordset::GetFieldValue(int nIndex, double& dbValue) { double val = (double)NULL; _variant_t vtFld; _variant_t vtIndex; vtIndex.vt = VT_I2; vtIndex.iVal = nIndex; try { vtFld = m_pRecordset->Fields->GetItem(vtIndex)->Value; switch(vtFld.vt) { case VT_R4: val = vtFld.fltVal; break; case VT_R8: val = vtFld.dblVal; break; case VT_DECIMAL: //Corrected by Jos?Carlos Mart�nez Gal�n val = vtFld.decVal.Lo32; val *= (vtFld.decVal.sign == 128)? -1 : 1; val /= pow(10.0, vtFld.decVal.scale); break; case VT_UI1: val = vtFld.iVal; break; case VT_I2: case VT_I4: val = vtFld.lVal; break; case VT_INT: val = vtFld.intVal; break; case VT_NULL: case VT_EMPTY: val = 0; break; default: val = 0; } dbValue = val; return TRUE; } catch(_com_error &e) { dump_com_error(e); return FALSE; } } BOOL CADORecordset::GetFieldValue(LPCTSTR lpFieldName, long& lValue) { long val = (long)NULL; _variant_t vtFld; try { vtFld = m_pRecordset->Fields->GetItem(lpFieldName)->Value; if(vtFld.vt !

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