使用ADO封装类的数据库程序开发实例

_ConnectionPtrpConnection;
LPCSTRstrConnect="Provider=Microsoft.Jet.OLEDB.4.0;DataSource=test.mdb";
//创建Connection对象---------------------------
HRESULThr=pConnection.CreateInstance("ADODB.Connection");
//设置连接时间-----------------------------------
pConnection->put_ConnectionTimeout(long(5));
if(SUCCEEDED(hr))
{
	//连接数据库---------------------------------------------
	pConnection->Open(strConnect,"","",adConnectUnspecified))
}

LPCSTRstrSQL="select*fromvckbasetable";
_RecordsetPtrpRecordset;
pRecordset.CreateInstance("ADODB.Recordset");
pRecordset->Open(_bstr_t(strSQL),
	_variant_t((IDispatch*)pConnection,true),
	adOpenStatic,
	AdLockOptimistic,
	adCmdText);

FieldsPtrpFields;
pRecordset->get_Fields(&pFields);
pFields->Item[L"COLUMN_NAME"]->Value;
//或pFields->Item[long(index)]->Value;
//其中index为整型或长整型.GetFields()函数返回的是记录集对象的字段集合对象的指针.

pRecordset->get_Collect("COLUMN_NAME");
//或pRecordset->get_Collect(long(index));

intncol=rset.GetFieldsCount();
while(!rset.IsEOF())
{
	for(inti=0;i<ncol;i++)
	{
		rset.GetValueString(value,(long)(i));
	}
	rset.MoveNext();
}

FieldsPtrpFields;
Recordset->get_Fields(&pFields);

longlIndex=0;
FieldPtrpf=pFields->GetItem(_variant_t(lIndex));
//或:FieldPtrpf=pFields->GetItem("COLUMN_NAME");

get_ActualSize(long*pl)//实际宽度
get_Attributes(long*pl)//属性
get_DefinedSize(long*pl)//定义宽度(以字节为单位,如整型为4，长整型为8...)
get_Name(BSTR*pbstr)	//字段名
get_Type(DataTypeEnum*pDataType)//数据类型
get_Value(VARIANT*pvar)//字段的值

五、开始编写ADO应用程序.

使用ADO之前，我们另外还需要添加下面的语句,如此把ADO的库引入到工程中.[code]#import"c:\programfiles\commonfiles\system\ado\msado15.dll"
no_namespacerename("EOF","adoEOF")

BOOLCAdoConnection::Connect(LPCTSTRstrConnect,longlOptions)
{
	m_strConnect=strConnect;
	try
	{
		///创建Connection对象---------------------------
		HRESULT	hr=m_pConnection.CreateInstance("ADODB.Connection");
		if(SUCCEEDED(hr))
		{
			//连接数据库---------------------------------------------
			if(SUCCEEDED(m_pConnection->Open(strConnect,"","",lOptions)))
			{	
				returnTRUE;
			}
		}
	}
	catch(_com_errore)
	{
		TRACE(_T(":(连接数据库发生错误:%s\n"),e.ErrorMessage());
		returnFALSE;
	}
	catch(...)
	{
		TRACE(_T(":(连接数据库时发生未知错误:"));
	}
	returnFALSE;
}

CStringstrSrcName="E:\\Access\\datebase.mdb";//假设在e盘有这样一个access的数据库文件
CStringstrConnect="Provider=Microsoft.Jet.OLEDB.4.0;DataSource="+strSrcName;
m_adoConnection.Connect(LPCSTR(strConnect));

HRESULTCAdoRecordSet::Open(LPCTSTRstrSQL,
			longlOption,
			CursorTypeEnumCursorType,
			LockTypeEnumLockType)
{
	try
	{
		if(m_pConnection==NULL)
		{
			return-1;
		}
		elseif(m_pRecordset==NULL)
		{
			m_pRecordset.CreateInstance("ADODB.Recordset");
		}
		
		m_pRecordset->Open(_bstr_t(strSQL),
			_variant_t((IDispatch*)m_pConnection->GetConnection(),true),
			CursorType,LockType,lOption);
		if(m_pRecordset==NULL)
		{
			return-1;
		}
		return(m_pRecordset->adoEOF)?0:1;
	}
	catch(_com_errore)
	{
		TRACE(_T(":(打开记录集发生错误:%s\n"),e.ErrorMessage());
		return-1;
	}
}

CAdoRecordSetrset;
rset.SetAdoConnection(&(GetDocument()->m_adoConnection));//记得要先指定相应的连接对象，否则会出错.
m_strSQL="select*fromcity";//要执行的SQL语句.
rset.Open(m_strSQL);

voidCAccessView::OnFileConnect()
{
	CLogoDigdlg;
	if(dlg.DoModal()==IDOK)
	{
		if(dlg.m_nSrcType==0)
		{
			CStringstrConnect="Provider=Microsoft.Jet.OLEDB.4.0;DataSource="+dlg.m_strSrcName;
			GetDocument()->m_adoConnection.Disconnect();
			if(!GetDocument()->m_adoConnection.Connect(LPCSTR(strConnect)))
			{
				AfxMessageBox("连接数据库失败!");
				return;
			}
		}
		elseif(dlg.m_nSrcType==1)
		{
			CStringstrConnect="Provider=SQLOLEDB.1;DataSource="+dlg.m_strSrcName+
					";InitialCatalog="+dlg.m_strDbName+
					";UserID="+dlg.m_strUserName+";PWD="+dlg.m_strPassWord;
			GetDocument()->m_adoConnection.Disconnect();
			if(!GetDocument()->m_adoConnection.Connect(LPCSTR(strConnect)))
			{
				AfxMessageBox("连接数据库失败!");
				return;
			}
		}
		((CMainFrame*)GetParentFrame())->m_wndLeftBar.InitTree();
	}
}

voidCAccessView::OnSize(UINTnType,intcx,intcy)
{
	CFormView::OnSize(nType,cx,cy);
	
	if(m_wndGrid.GetSafeHwnd()!=NULL)//控件是否已经创建
	{
		m_editError.MoveWindow(0,10,cx,cy-50);
		m_wndGrid.MoveWindow(0,0,cx,cy-40);
		m_editSQL.MoveWindow(0,cy-40,cx,40);
	}
}

voidCAccessView::OnRun()
{
	UpdateData();
	UpdateGrid();
}

voidCAccessView::UpdateGrid()
{
	//连接对象是否打开------------------------------------------
	if(!GetDocument()->m_adoConnection.IsOpen())
	{
		AfxMessageBox("数据库没有打开或已经关闭!");
		return;
	}
	//先隐藏这两个控件------------------------------------------
	m_wndGrid.ShowWindow(SW_HIDE);
	m_editError.ShowWindow(SW_HIDE);

	CAdoRecordSetrset;
	rset.SetAdoConnection(&(GetDocument()->m_adoConnection));
	if(rset.Open(m_strSQL,adCmdText)!=1)
	{
		//查询出错，取得出错信息并显示在编辑控件里面------------------
		m_strError=GetDocument()->m_adoConnection.GetLastError();
		UpdateData(FALSE);
		m_editError.ShowWindow(SW_SHOW);
		return;
	}
	//下面我用到的有些函数在类中可能没有封装，所以还是使用了try块,以防万一,:(
	try
	{
		//取得记录集的字段数和行数----------------------------------
		intnrow=rset.GetRecordCount();
		intncol=rset.GetFields()->Count;
		//设置网格控件的列数和行数----------------------------------
		m_wndGrid.SetCols(ncol);
		m_wndGrid.SetRows(nrow+1);//多留一行以显示字段名
		m_wndGrid.SetFixedCols(0);
		
		CStringvalue;
		//填充字段名-----------------------------------------------
		m_wndGrid.SetRow(0);
		for(inti=0;i<ncol;i++)
		{
			m_wndGrid.SetCol(i);
			m_wndGrid.SetText(LPCSTR(rset.GetFieldName(i)));
			//设置当前列的大致宽度-------------------------------
			intnwidth=rset.GetFieldDefineSize(i)*200;
			nwidth=nwidth>2000?2000:nwidth;
			m_wndGrid.SetColWidth(i,nwidth);
		}
		
		//读取记录集-----------------------------------------------
		intn=1;
		while(!rset.IsEOF())
		{
			m_wndGrid.SetRow(n);
			n++;
			for(inti=0;i<ncol;i++)
			{
				m_wndGrid.SetCol(i);
				rset.GetValueString(value,(long)(i));
				m_wndGrid.SetText(LPCTSTR(value));
			}
			rset.MoveNext();
		}
		m_wndGrid.ShowWindow(SW_SHOW);
	}
	catch(_com_error)
	{
		return;
	}
}

voidCLeftBar::InitTree()
{
	CAdoRecordSetrset;
	_bstr_tValue;
	CStringstrTablename="";
	HTREEITEMitem=TVI_ROOT;
	try
	{
		if(GetDocument()->m_adoConnection.GetConnection()->State!=adStateOpen)return;
		m_ctrlTree.DeleteAllItems();
		//取得数据库字段信息---------------------------------------------
		rset=GetDocument()->m_adoConnection.OpenSchema(adSchemaColumns);
		while(!rset.IsEOF())
		{
			CStringstrValue;
			//取得表名-----------------------------------------------
			rset.GetValueString(strValue,"TABLE_NAME");
			if(strValue!=strTablename)
			{
				strTablename=strValue;
				item=m_ctrlTree.InsertItem((LPCTSTR)strTablename,1,1);
			}
			//取得字段名--------------------------------------------
			Value=rset.GetFields()->Item[L"COLUMN_NAME"]->Value;
			m_ctrlTree.InsertItem((LPCTSTR)Value,2,2,item);
			
			rset.MoveNext();
		}
	}
	catch(_com_errore)
	{
		
	}
}