(二)在vb中的处理 在vb中处理大对象,一般可以用OO4O(oracle objects for ole)来处理大对象。这里介绍一种不用0040处理大对象blob的方法。 下面这段程序可以将一个文件(文本文件,doc文件,图象文件等)保存到数据库中,并可以将其从数据库读出 需要两个commandbutton cmd1 名称 cmdsave caption 保存 cmd2 名称 cmdread caption 读取 一个cmddialog控件 同时需要创建一张表t_demo(字段id 类型 number,;字段text 类型 blob;) exmple 3. Option Explicit Dim rn As ADODB.Connection Public Function CreateDataSource(DataSource As String, UserID As String, Password As String) As Boolean On Error GoTo DbConErr: Set rn = New ADODB.Connection With rn .ConnectionString = "Provider=OraOledb.Oracle.1;" & _ "password=" & Password & ";" & _ "User ID =" & UserID & ";" & _ "Data Source=" & DataSource & ";" & _ "Locale Identifier=2052" .Open End With CreateDataSource = True Exit Function DbConErr: CreateDataSource = False End FunctionPrivate Sub cmdRead_Click() Dim rs As New ADODB.Recordset rs.ActiveConnection = rn rs.LockType = adLockOptimistic rs.CursorLocation = adUseClient rs.Source = "select * from t_demo" rs.Open ComDlgDir.DialogTitle = "保存文件" ComDlgDir.Filter = "*.*" ComDlgDir.ShowSave Call BlobToFile(rs.Fields("text"), ComDlgDir.filename) Set rs = Nothing Exit Sub Set rs = Nothing End SubPrivate Sub cmdsave_Click() Dim rs As New ADODB.Recordset rs.ActiveConnection = rn rs.LockType = adLockOptimistic rs.CursorLocation = adUseClient rs.Source = "select * from t_demo" rs.Open rs.AddNew ComDlgDir.DialogTitle = "选取文件" ComDlgDir.ShowOpen rs.Fields("id").Value = 1 If ComDlgDir.filename <> "" Then Call FileToBlob(rs.Fields("text"), ComDlgDir.filename) rs.Update End If Set rs = Nothing Exit Sub Set rs = Nothing End SubPrivate Sub Form_Load() If Not CreateDataSource("sid", "systemp", "manager") Then MsgBox "Connection failure!" End If End Subfld As ADODB.Field, filename As String, Optional ChunkSize As Long = 8192) Dim fnum As Integer, bytesleft As Long, bytes As Long Dim tmp() As Byte If (fld.Attributes And adFldLong) = 0 Then Err.Raise 1001, , "field doesn't support the GetChunk method." End If If Dir$(filename) = "" Then Err.Raise 53, , "File not found" fnum = FreeFile Open filename For Binary As fnum bytesleft = LOF(fnum) Do While bytesleft bytes = bytesleft If bytes > ChunkSize Then bytes = ChunkSize ReDim tmp(1 To bytes) As Byte Get fnum, , tmp fld.AppendChunk tmp bytesleft = bytesleft - bytes Loop Close #fnum End SubSub BlobToFile(fld As ADODB.Field, filename As String, Optional ChunkSize As Long = 8192) Dim fnum As Integer, bytesleft As Long, bytes As Long Dim tmp() As Byte If (fld.Attributes And adFldLong) = 0 Then Err.Raise 1001, , "field doesn't support the GetChunk method." End If If Dir$(filename) <> "" Then Kill filename fnum = FreeFile Open filename For Binary As fnum bytesleft = fld.ActualSize Do While bytesleft bytes = bytesleft If bytes > ChunkSize Then bytes = ChunkSize tmp = fld.GetChunk(bytes) Put #fnum, , tmp bytesleft = bytesleft - bytes Loop Close #fnum End Sub
在vb中处理大对象,一般可以用OO4O(oracle objects for ole)来处理大对象。这里介绍一种不用0040处理大对象blob的方法。
下面这段程序可以将一个文件(文本文件,doc文件,图象文件等)保存到数据库中,并可以将其从数据库读出
需要两个commandbutton
cmd1 名称 cmdsave caption 保存
cmd2 名称 cmdread caption 读取
一个cmddialog控件
同时需要创建一张表t_demo(字段id 类型 number,;字段text 类型 blob;)
exmple 3.
Option Explicit
Dim rn As ADODB.Connection
Public Function CreateDataSource(DataSource As String, UserID As String, Password As String) As Boolean
On Error GoTo DbConErr:
Set rn = New ADODB.Connection
With rn
.ConnectionString = "Provider=OraOledb.Oracle.1;" & _
"password=" & Password & ";" & _
"User ID =" & UserID & ";" & _
"Data Source=" & DataSource & ";" & _
"Locale Identifier=2052"
.Open
End With
CreateDataSource = True
Exit Function
DbConErr:
CreateDataSource = False
End FunctionPrivate Sub cmdRead_Click()
Dim rs As New ADODB.Recordset
rs.ActiveConnection = rn
rs.LockType = adLockOptimistic
rs.CursorLocation = adUseClient
rs.Source = "select * from t_demo"
rs.Open
ComDlgDir.DialogTitle = "保存文件"
ComDlgDir.Filter = "*.*"
ComDlgDir.ShowSave
Call BlobToFile(rs.Fields("text"), ComDlgDir.filename)
Set rs = Nothing
Exit Sub
Set rs = Nothing
End SubPrivate Sub cmdsave_Click()
Dim rs As New ADODB.Recordset
rs.ActiveConnection = rn
rs.LockType = adLockOptimistic
rs.CursorLocation = adUseClient
rs.Source = "select * from t_demo"
rs.Open
rs.AddNew
ComDlgDir.DialogTitle = "选取文件"
ComDlgDir.ShowOpen
rs.Fields("id").Value = 1
If ComDlgDir.filename <> "" Then
Call FileToBlob(rs.Fields("text"), ComDlgDir.filename)
rs.Update
End If
Set rs = Nothing
Exit Sub
Set rs = Nothing
End SubPrivate Sub Form_Load()
If Not CreateDataSource("sid", "systemp", "manager") Then
MsgBox "Connection failure!"
End If
End Subfld As ADODB.Field, filename As String, Optional ChunkSize As Long = 8192)
Dim fnum As Integer, bytesleft As Long, bytes As Long
Dim tmp() As Byte
If (fld.Attributes And adFldLong) = 0 Then
Err.Raise 1001, , "field doesn't support the GetChunk method."
End If
If Dir$(filename) = "" Then Err.Raise 53, , "File not found"
fnum = FreeFile
Open filename For Binary As fnum
bytesleft = LOF(fnum)
Do While bytesleft
bytes = bytesleft
If bytes > ChunkSize Then bytes = ChunkSize
ReDim tmp(1 To bytes) As Byte
Get fnum, , tmp
fld.AppendChunk tmp
bytesleft = bytesleft - bytes
Loop
Close #fnum
End SubSub BlobToFile(fld As ADODB.Field, filename As String, Optional ChunkSize As Long = 8192)
Dim fnum As Integer, bytesleft As Long, bytes As Long
Dim tmp() As Byte
If (fld.Attributes And adFldLong) = 0 Then
Err.Raise 1001, , "field doesn't support the GetChunk method."
End If
If Dir$(filename) <> "" Then Kill filename
fnum = FreeFile
Open filename For Binary As fnum
bytesleft = fld.ActualSize
Do While bytesleft
bytes = bytesleft
If bytes > ChunkSize Then bytes = ChunkSize
tmp = fld.GetChunk(bytes)
Put #fnum, , tmp
bytesleft = bytesleft - bytes
Loop
Close #fnum
End Sub
http://www.csdn.net/expert/topic/580/580137.xml?temp=3.103274E-02
select * from blob_table会出现有“数据类型不一致”!的错误,该怎么办
我做后台,前台的同事用的VB.net,他说在VB.net中不能用6.0下可以用的AppendChunk()和GetChunk()等函数,所以想请教各位在VB.net下如何用OO¥O处理BLOB对象?