Visual C++多线程DAO处理(1)

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更新时间：2005-11-04 14:50
关 键 词：D  C  I  多线程  s
阅读提示：在类中使用了GUI的消息队列，所有进入到CMultiDAORecordset的调用都被迫使用AfxGetThread()来检查当前的线程。

在DAO多线程处理中，有许多局限性，所以我设计了这么一个类，通过GUI线程来使用DAO的强制调用。在类中使用了GUI的消息队列，所有进入到CMultiDAORecordset的调用都被迫使用AfxGetThread()来检查当前的线程。GUI线程指针是放在InitInstance的首端，如果在GUI线程中，引入的调用请求不在运行，那么CMultiDAORecordSet就会 发送一个WM_MULTIDAOMESSAGE消息给AfxGetMainWnd()（在Mainfrm.cpp中）。Mainfrm接受到这个消息，线程也就要再运行一次，这个时候，消息已经接受了，基类CDaoRecordset也就得到了调用。所以你的类是从CMultiDAORecordset继承的，而不是CDaoRecordset，如下：
class CMySet : public CMultiDaoRecordSet
在相应的CPP文件中也应该改一下：
IMPLEMENT_DYNAMIC(CMySet, CMultiDaoRecordSet)
CMySet::CMySet (CDaoDatabase* pdb) : CMultiDaoRecordSet(pdb)
为了处理接受到的WM_MULTIDAOMESSAGE消息，下面的代码还应该加在MainFrm中：
在MainFrm.h文件中加：
#ifdef MAINFRAME_CPP
UINT WM_MULTIDAOMESSAGE = RegisterWindowMessage("WM_MULTIDAOMESSAGE");
#else
extern UINT WM_MULTIDAOMESSAGE;
#endif
afx_msg LONG OnMultiDaoMessage( UINT uParam, LONG lParam);
在MainFrm.cpp文件中加：
#define MAINFRAME_CPP
#include "MutliDaoRecordset.h"
//added to the message map
BEGIN_MESSAGE_MAP(CMainFrame, CMDIFrameWnd)
//{{AFX_MSG_MAP(CMainFrame)
ON_REGISTERED_MESSAGE(WM_MULTIDAOMESSAGE, OnMultiDaoMessage)
END_MESSAGE_MAP()
//this function added
LONG CMainFrame::OnMultiDaoMessage( UINT uParam, LONG lParam)
{
//jtm
//based on switch, perform operation...
CMultiDaoRecordSet *pSet = (CMultiDaoRecordSet *)lParam;
LONG lRet = 0;
CString cRet = "";
COleVariant cVar;
try
{
//jtm-------debug--------------------------------------
CString cTraceMessage = cDAOMessageArray[uParam];
cTraceMessage += "\n";
TRACE(cTraceMessage);
//jtm-------debug--------------------------------------
switch(uParam)
{
case MultiDaoOpen:
pSet->Open();
break;
case MultiDaoClose:
pSet->Close();
break;
case MultiDaoIsOpen:
lRet = (LONG)pSet->IsOpen();
break;
case MultiDaoIsBOF:
lRet = (LONG)pSet->IsBOF();
break;
case MultiDaoIsEOF:
lRet = (LONG)pSet->IsEOF();
break;
case MultiDaoIsDeleted:
lRet = (LONG)pSet->IsDeleted();
break;
case MultiDaoIsFieldDirty:
lRet = (LONG)pSet->IsFieldDirty(pSet->pParam1);
break;
case MultiDaoIsFieldNull:
lRet = (LONG)pSet->IsFieldNull(pSet->pParam1);
break;
case MultiDaoIsFieldNullable:
lRet = (LONG)pSet->IsFieldNullable(pSet->pParam1);
break;
case MultiDaoGetName:
cRet = pSet->GetName();
lRet = (LONG)&cRet;
break;
case MultiDaoGetType:
lRet = (LONG)pSet->GetType();
break;
case MultiDaoGetEditMode:
lRet = (LONG)pSet->GetEditMode();
break;
case MultiDaoGetLastModifiedBookmark:
cVar = pSet->GetLastModifiedBookmark();
lRet = (LONG)&cVar;
break;
case MultiDaoGetRecordCount:
lRet = (LONG)pSet->GetRecordCount();
break;
case MultiDaoMoveNext:
pSet->MoveNext();
break;
case MultiDaoMovePrev:
pSet->MovePrev();
break;
case MultiDaoMoveFirst:
pSet->MoveFirst();
break;
case MultiDaoMoveLast:
pSet->MoveLast();
break;
case MultiDaoMove:
pSet->Move(*(LONG *)pSet->pParam1);
break;
case MultiDaoFindNext:
lRet = (LONG)pSet->FindNext(*(LPCTSTR *)pSet->pParam1);
break;
case MultiDaoFindPrev:
lRet = (LONG)pSet->FindPrev(*(LPCTSTR*)pSet->pParam1);
break;
case MultiDaoFindFirst:
lRet = (LONG)pSet->FindFirst(*(LPCTSTR *)pSet->pParam1);
break;
case MultiDaoFindLast:
lRet = (LONG)pSet->FindLast(*(LPCTSTR *)pSet->pParam1);
break;
case MultiDaoFind:
lRet = (LONG)pSet->Find(*(LONG *)pSet->pParam1, *(LPCTSTR*)pSet->pParam2);
break;
case MultiDaoGetBookmark:
cVar = pSet->GetBookmark();
lRet = (LONG)&cVar;
break;
case MultiDaoSetBookmark:
pSet->SetBookmark(*(COleVariant*)pSet->pParam1);
break;
case MultiDaoAddNew:
pSet->AddNew();
break;
case MultiDaoEdit:
pSet->Edit();
break;
case MultiDaoUpdate:
pSet->Update();
break;
case MultiDaoDelete:
pSet->Delete();
break;
case MultiDaoCancelUpdate:
pSet->CancelUpdate();
break;
case MultiDaoRequery:
pSet->Requery();
break;
}
}
catch (CDaoException *e)
{
TRACE("Database Multithread Operation Failed%s\n",
e->m_pErrorInfo->m_strDescription);
}
return lRet;
}
下面的代码是加在对应的应用程序对象的头文件中的：
public:
CWinThread *pGUIThread;
And this to the constructor in the app .cpp file:
CMyApp::CMyApp()
{
pGUIThread = AfxGetThread();
}

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