::CoInitialize(NULL); //初始化OLE/COM库环境
_ConnectionPtr m_pConn;
try
{
    HRESULT hr = m_pConn.CreateInstance("ADODB.Connection");
    if(FAILED(hr))
    {
        cout<<"Create ADO Connection failed"<<endl;
        exit(0);
    }
    
    CString oracleConnectionString, oracleUserID, oraclePassword;
    oracleConnectionString = "Provider=MSDAORA;Data Source=STUDENT;";
    oracleUserID = "stuinfo";
    oraclePassword = "stuinfo";
    
    hr = m_pConn->Open((_bstr_t)oracleConnectionString, (_bstr_t)oracleUserID, (_bstr_t)oraclePassword, adModeUnknown);
    if (FAILED(hr))
    {
        cout<<"Can not connect to database"<<endl;
        exit(0);
    }
    else
    {
        cout<<"Connect to database successfully!"<<endl;
    }
}
catch(_com_error e)
{
    CString errMsg = e.ErrorMessage();
    cout<<errMsg<<endl;
    exit(0);
}

_RecordsetPtr m_pRecordset;
try
{
    
    HRESULT hr = m_pRecordset.CreateInstance("ADODB.Recordset");
    if (FAILED(hr))
    {
        cout<<"Create ADO Recordset failed"<<endl;
        exit(0);
    }
    
    CString strSQL = "select * from stuinfotable where stuid=1";
    // stuinfotable表中有一个blob类型字段stupic存储照片
    BSTR bstrSQL = strSQL.AllocSysString(); 
    hr = m_pRecordset->Open(bstrSQL, (IDispatch*)m_pConn, adOpenDynamic, adLockOptimistic, adCmdText);
    if (FAILED(hr))
    {
        cout<<"Open ADO Recordset failed"<<endl;
        exit(0);
    }
}
catch(_com_error e)
{
    CString errMsg = e.ErrorMessage();
    cout<<errMsg<<endl;
    exit(0);
}

long lDataSize = m_pRecordset->GetFields()->GetItem("stupic")->ActualSize;
cout<<"BLOB length is "<<lDataSize<<endl;

if(lDataSize > 0)
{
    _variant_t varBLOB;
    varBLOB = m_pRecordset->GetFields()->GetItem("stupic")->GetChunk(lDataSize);
    
    //判断数据类型是否正确
    if(varBLOB.vt == (VT_ARRAY | VT_UI1))
    {
        BYTE *pBuf = NULL;
        //得到指向数据的指针
        SafeArrayAccessData(varBLOB.parray, (void **)&pBuf);
        /**//***这里是对pBuf数据的处理***/
        CFile targetImageFile;
        CFileException eTargetImageFile;
        CString targetImageFileName = "C:\\stupicture.bmp";

        if (!targetImageFile.Open(targetImageFileName, CFile::modeCreate | CFile::modeWrite, &eTargetImageFile))
        {
            cout<<"Create file failed"<<endl;
            exit(0);
        }
        else
        {
            // 打开文件成功，准备写入
            targetImageFile.Write((BYTE *)pBuf, lDataSize);
            cout<<"Write stupicture.bmp file successfully!"<<endl;
        }
        SafeArrayUnaccessData (varBLOB.parray);
    }
}

// 断开ADO连接
if (m_pConn != NULL)
{
    m_pConn->Close();
    m_pConn = NULL;
    cout<<"ADO connection closed successfully"<<endl;
}

::CoUninitialize();//释放程序占用的COM 资源

m_pRecordset->Open(bstrSQL, (IDispatch*)m_pConn, adOpenDynamic, adLockOptimistic, adCmdText);