accessblobdlg.cpp

请读者确保您的计算机上已经安装了基于VC的数据库开发与工程实践随盘光盘

// AccessBlobDlg.cpp : implementation file
//

#include "stdafx.h"
#include "AccessBlob.h"
#include "AccessBlobDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

#define ChunkSize 1024
/////////////////////////////////////////////////////////////////////////////
// CAboutDlg dialog used for App About

class CAboutDlg : public CDialog
{
public:
	CAboutDlg();

// Dialog Data
	//{{AFX_DATA(CAboutDlg)
	enum { IDD = IDD_ABOUTBOX };
	//}}AFX_DATA

	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CAboutDlg)
	protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
	//}}AFX_VIRTUAL

// Implementation
protected:
	//{{AFX_MSG(CAboutDlg)
	//}}AFX_MSG
	DECLARE_MESSAGE_MAP()
};

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
	//{{AFX_DATA_INIT(CAboutDlg)
	//}}AFX_DATA_INIT
}

void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CAboutDlg)
	//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
	//{{AFX_MSG_MAP(CAboutDlg)
		// No message handlers
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CAccessBlobDlg dialog

CAccessBlobDlg::CAccessBlobDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CAccessBlobDlg::IDD, pParent)
{
	//{{AFX_DATA_INIT(CAccessBlobDlg)
	m_strName = _T("");
	m_strSuffix = _T("");
	m_strFilePath = _T("");
	//}}AFX_DATA_INIT
	// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
	m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void CAccessBlobDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CAccessBlobDlg)
	DDX_Text(pDX, IDC_EDIT_NAME, m_strName);
	DDX_Text(pDX, IDC_EDIT_SUFFIX, m_strSuffix);
	DDX_Text(pDX, IDC_EDIT_FILEPATH, m_strFilePath);
	//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CAccessBlobDlg, CDialog)
	//{{AFX_MSG_MAP(CAccessBlobDlg)
	ON_WM_SYSCOMMAND()
	ON_WM_PAINT()
	ON_WM_QUERYDRAGICON()
	ON_BN_CLICKED(IDC_BUTTON_PREV, OnButtonPrev)
	ON_BN_CLICKED(IDC_BUTTON_NEXT, OnButtonNext)
	ON_BN_CLICKED(IDC_BUTTON_ADD, OnButtonAdd)
	ON_BN_CLICKED(IDC_BUTTON_READ, OnButtonRead)
	ON_WM_DESTROY()
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CAccessBlobDlg message handlers

BOOL CAccessBlobDlg::OnInitDialog()
{
	CDialog::OnInitDialog();

	// Add "About..." menu item to system menu.

	// IDM_ABOUTBOX must be in the system command range.
	ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
	ASSERT(IDM_ABOUTBOX < 0xF000);

	CMenu* pSysMenu = GetSystemMenu(FALSE);
	if (pSysMenu != NULL)
	{
		CString strAboutMenu;
		strAboutMenu.LoadString(IDS_ABOUTBOX);
		if (!strAboutMenu.IsEmpty())
		{
			pSysMenu->AppendMenu(MF_SEPARATOR);
			pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
		}
	}

	// Set the icon for this dialog.  The framework does this automatically
	//  when the application's main window is not a dialog
	SetIcon(m_hIcon, TRUE);			// Set big icon
	SetIcon(m_hIcon, FALSE);		// Set small icon
	
	// TODO: Add extra initialization here
	//初始化com环境
	::CoInitialize(NULL);
	//创建连接对象和记录集对象
	HRESULT hr;
	try
	{
		hr = m_pConnection.CreateInstance("ADODB.Connection");//创建Connection对象
		if(SUCCEEDED(hr))
		{
			hr = m_pConnection->Open(
				"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=blob.mdb",
				"","",adModeUnknown);
		}
	}
	catch(_com_error e)///捕捉异常
	{
		CString errormessage;
		errormessage.Format("连接数据库失败!\r\n错误信息:%s",e.ErrorMessage());
		AfxMessageBox(errormessage);///显示错误信息
	}
	m_pRecordset.CreateInstance(__uuidof(Recordset));
	hr = m_pRecordset->Open("SELECT * FROM blob",
		_variant_t((IDispatch *)m_pConnection,true),
		adOpenDynamic,adLockPessimistic,adCmdText);
    if(SUCCEEDED(hr))
	{
		ReadData();
	}
	return TRUE;  // return TRUE  unless you set the focus to a control
}

void CAccessBlobDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
	if ((nID & 0xFFF0) == IDM_ABOUTBOX)
	{
		CAboutDlg dlgAbout;
		dlgAbout.DoModal();
	}
	else
	{
		CDialog::OnSysCommand(nID, lParam);
	}
}

// If you add a minimize button to your dialog, you will need the code below
//  to draw the icon.  For MFC applications using the document/view model,
//  this is automatically done for you by the framework.

void CAccessBlobDlg::OnPaint() 
{
	if (IsIconic())
	{
		CPaintDC dc(this); // device context for painting

		SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// Draw the icon
		dc.DrawIcon(x, y, m_hIcon);
	}
	else
	{
		CDialog::OnPaint();
	}
}

// The system calls this to obtain the cursor to display while the user drags
//  the minimized window.
HCURSOR CAccessBlobDlg::OnQueryDragIcon()
{
	return (HCURSOR) m_hIcon;
}

//将当前记录的名称和后缀显示出来
void CAccessBlobDlg::ReadData()
{
	//判断是否在第一条记录和最后一条记录
	if(m_pRecordset->adoEOF||m_pRecordset->BOF) 
	{
		m_strName.Empty();
		m_strSuffix.Empty();
		UpdateData(FALSE);
		return;
	}
	m_strName = m_pRecordset->GetCollect("name").bstrVal;
	m_strSuffix = m_pRecordset->GetCollect("suffix").bstrVal;
	UpdateData(FALSE);
}

//写入二进制文件到数据库
void CAccessBlobDlg::FileToDb(CString strPath)
{	
	VARIANT varChunk;
	SAFEARRAY *psa;
	SAFEARRAYBOUND rgsabound[1]; 
	
	//VT_ARRAY | VT_UI1
	CFile f(strPath,CFile::modeRead);
	BYTE  bVal[ChunkSize+1];
	UINT uIsRead=0;
	//Create a safe array to store the array of BYTES  
	while(1)
	{
		uIsRead=f.Read(bVal,ChunkSize);
		if(uIsRead==0)break;
		rgsabound[0].cElements =uIsRead;
		rgsabound[0].lLbound = 0;

		///创建SAFEARRAY对象
		psa = SafeArrayCreate(VT_UI1,1,rgsabound);

		for(long index=0;index<uIsRead;index++)          
		{
			if(FAILED(SafeArrayPutElement(psa,&index,&bVal[index])))
				::MessageBox(NULL,"错误。","提示",MB_OK | MB_ICONWARNING);
		}

		//为varChunk变量赋值
		varChunk.vt = VT_ARRAY|VT_UI1;
		varChunk.parray = psa;

		//加入BLOB类型的数据
		try{
			m_pRecordset->Fields->GetItem("data")->AppendChunk(varChunk); 
		}
		catch (_com_error &e)
		{
			CString str=(char*)e.Description();
			::MessageBox(NULL,str+"\n错误。","提示",MB_OK | MB_ICONWARNING);
		}
		::VariantClear(&varChunk);
		::SafeArrayDestroyData( psa);
		if(uIsRead<ChunkSize)break;
	}
	m_pRecordset->Update();
	f.Close(); 
}

//从数据库读出二进制对象到文件
void CAccessBlobDlg::DbToFile(CString strPath)
{	
	CFile f;
	f.Open(strPath,CFile::modeWrite|CFile::modeCreate);
	long lPhotoSize = m_pRecordset->Fields->Item["data"]->ActualSize;  
	long lIsRead=0; 
	
	_variant_t varChunk;
	BYTE buf[ChunkSize];
	while(lPhotoSize>0)
	{
		lIsRead=lPhotoSize>=ChunkSize? ChunkSize:lPhotoSize;

		//从字段data中获取一个数据包
		varChunk = m_pRecordset->Fields->
			Item["data"]->GetChunk(lIsRead);
		for(long index=0;index<lIsRead;index++)         
		{           
			::SafeArrayGetElement(varChunk.parray,&index,buf+index);   
		}

		//将数据包写入文件
		f.Write(buf,lIsRead);
		lPhotoSize-=lIsRead;
	}
	f.Close();
}

void CAccessBlobDlg::OnButtonPrev() 
{
	m_pRecordset->MovePrevious();
	if(m_pRecordset->BOF)
		m_pRecordset->MoveFirst();
	ReadData();
}

void CAccessBlobDlg::OnButtonNext() 
{
	m_pRecordset->MoveNext();
	if(m_pRecordset->adoEOF)
		m_pRecordset->MoveLast();
	ReadData();
}

void CAccessBlobDlg::OnButtonAdd() 
{
	UpdateData(TRUE);
	//弹出选择文件的对话框
	static char BASED_CODE szFilter[] = "All Files (*.*)|*.*||";
	CFileDialog dlg(TRUE,NULL,NULL,OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT,
		szFilter,NULL);
	if(dlg.DoModal() == IDOK)
	{
		//增加新记录
		m_pRecordset->AddNew();
		m_pRecordset->PutCollect("name",_variant_t(m_strName));
		CString strSuffix = "." + dlg.GetFileExt();
		m_pRecordset->PutCollect("suffix",_variant_t(strSuffix));
		m_pRecordset->Update();

		//写二进制文件到数据库
		FileToDb(dlg.GetPathName());
		AfxMessageBox("入库完毕！");
		m_strSuffix = strSuffix;
		UpdateData(FALSE);
	}
}

void CAccessBlobDlg::OnButtonRead() 
{
	UpdateData(TRUE);
	DbToFile(m_strFilePath);
	AfxMessageBox("输出完毕！");
}

//还原COM环境，并关闭记录对象和连接
void CAccessBlobDlg::OnDestroy() 
{
//	if(m_pRecordset->State)
		m_pRecordset->Close();
//	m_pRecordset->Release();
	if(m_pConnection->State)
		m_pConnection->Close();
	m_pConnection.Release();
	::CoUninitialize();

	CDialog::OnDestroy();
}