使用ADO读取数据库中的二进制文件

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1. //JPG图片保存到数据库

2. try

3. {

4. _RecordsetPtr pRecordset;

5. pRecordset.CreateInstance(__uuidof(Recordset));

6. pRecordset->Open("SELECT * FROM jpg",_variant_t((IDispatch*)pConnection),adOpenStatic,adLockOptimistic,adCmdText);

7. pRecordset->AddNew();

8. pRecordset->Fields->Item["jpgid"]->Value = (_variant_t)m_JPGId;//jpgid

9. VARIANT pvList;

10. SetPictureToVariant(pvList,(unsigned char *)m_pJPGBuffer);

11. pRecordset->Fields->Item["jpgimage"]->AppendChunk(pvList); //JPG图像文件

12. VariantClear(&pvList);

13.

14. pRecordset->Update();

15. pRecordset->Close();

16. AfxMessageBox("JPG图像保存成功！");

17. m_JPGId == "";

18. UpdateData(false);

19. }

20. catch(...)

21. {

22. AfxMessageBox("数据库读取失败");

23. return;

24. }

//JPG图片保存到数据库
try
{
_RecordsetPtr pRecordset;
pRecordset.CreateInstance(__uuidof(Recordset));
pRecordset->Open("SELECT * FROM jpg",_variant_t((IDispatch*)pConnection),adOpenStatic,adLockOptimistic,adCmdText);
pRecordset->AddNew();
pRecordset->Fields->Item["jpgid"]->Value = (_variant_t)m_JPGId;//jpgid
VARIANT pvList;
SetPictureToVariant(pvList,(unsigned char *)m_pJPGBuffer);
pRecordset->Fields->Item["jpgimage"]->AppendChunk(pvList); //JPG图像文件
VariantClear(&pvList);
pRecordset->Update();
pRecordset->Close();
AfxMessageBox("JPG图像保存成功！");
m_JPGId == "";
UpdateData(false);
}
catch(...)
{
AfxMessageBox("数据库读取失败");
return;
}

其中SetPictureToVariant如下：

以下是代码片段：

查看源代码拷贝至剪贴板打印代码

1. void CBMPinDBDlg::SetPictureToVariant(VARIANT &pvList, unsigned char *sPicture)

2. {

3. SAFEARRAYBOUND saBound[1];

4. saBound[0].cElements = m_nFileLen;

5. saBound[0].lLbound = 0;

6. SAFEARRAY *pSA = SafeArrayCreate(VT_UI1, 1, saBound);

7. for (long l = 0; l < (long)m_nFileLen; l ++)

8. {

9. SafeArrayPutElement( pSA, &l, (void*)&sPicture[l]);

10. }

11. VariantClear(&pvList);

12. pvList.vt = VT_UI1 | VT_ARRAY;

13. pvList.parray = pSA;

14. }

void CBMPinDBDlg::SetPictureToVariant(VARIANT &pvList, unsigned char *sPicture)
{
SAFEARRAYBOUND saBound[1];
saBound[0].cElements = m_nFileLen;
saBound[0].lLbound = 0;
SAFEARRAY *pSA = SafeArrayCreate(VT_UI1, 1, saBound);
for (long l = 0; l < (long)m_nFileLen; l ++)
{
SafeArrayPutElement( pSA, &l, (void*)&sPicture[l]);
}
VariantClear(&pvList);
pvList.vt = VT_UI1 | VT_ARRAY;
pvList.parray = pSA;
}

2、从数据库读取图像文件并且显示在界面

以下是代码片段：

查看源代码拷贝至剪贴板打印代码

1. //从数据库里取JPG图像文件

2. try

3. {

4. _RecordsetPtr pRecordset;

5. char sSql[129];

6. sprintf(sSql,"SELECT *FROM jpg WHERE jpgid=’%s’",m_JPGId);

7. pRecordset.CreateInstance(__uuidof(Recordset));

8. pRecordset->Open(sSql,_variant_t((IDispatch*)pConnection),adOpenStatic,adLockOptimistic,adCmdText);

9. if (pRecordset->adoEOF)

10. {

11. CString str;

12. str.Format("没有JPGid为: %s 的JPG图像!",m_JPGId );

13. AfxMessageBox(str);

14. Invalidate();

15. m_JPGId = "";

16. UpdateData(false);

17. m_EidtJPGId.SetFocus();

18. return;

19. }

20. _variant_t pvList ;

21. long lDataSize = pRecordset->GetFields()->GetItem("jpgimage")->ActualSize;

22. m_nFileLen = (DWORD)lDataSize;

23. if(lDataSize > 0)

24. {

25. _variant_t varBLOB;

26. varBLOB = pRecordset->GetFields()->GetItem("jpgimage")->GetChunk(lDataSize);

27. //把二进制格式的图片转为图片格式

28. try

29. {

30. if(varBLOB.vt == (VT_ARRAY | VT_UI1))

31. {

32. if(m_pJPGBuffer = new char[lDataSize+1])

33. {

34. char *pBuf = NULL;

35. SafeArrayAccessData(varBLOB.parray,(void **)&pBuf);

36. memcpy(m_pJPGBuffer,pBuf,lDataSize);

37. SafeArrayUnaccessData (varBLOB.parray);

38. m_nFileLen = lDataSize;

39.

40. //m_pJPGBuffer -> pPicture

41. HGLOBAL hMem = ::GlobalAlloc( GMEM_MOVEABLE, m_nFileLen );

42. LPVOID lpBuf = ::GlobalLock( hMem );

43. memcpy(lpBuf,m_pJPGBuffer,m_nFileLen);

44.

45. ::GlobalUnlock( hMem );

46.

47. if ( CreateStreamOnHGlobal( hMem, TRUE, &pStream ) !=S_OK )

48. return ;

49.

50. if ( OleLoadPicture( pStream, m_nFileLen, TRUE, IID_IPicture, ( LPVOID * )&pPicture ) !=S_OK )

51. return ;

52.

53. Invalidate();//在界面显示

54. }

55. }

56. }

57. catch(...)

58. {

59. AfxMessageBox("从数据库中读取jpg图像有错！");

60. return;

61. }

62.

63. }

64.

65. }

66. catch(...)

67. {

68. AfxMessageBox("数据库读取失败");

69. return;

70. }

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