Blob参数在多层中如何传递？
ADO+SQL Server 2K+Delphi 5+miads做的三层结构．
中间层RDM自定了一个接口，有一个参数为olevariant类型，把数据库中的image类型的数据
传给Client,想通TMemoryStream把数据读到olevariant中，失败．
问题1:如何把一个TMemoryStream中的数据读到一个olevariant型变量中？
问题2:如上面描述，有否其他方法实现？如何做？
问题1：
fcontent:olevariant;
p:pointer;
stream:tmemorystream;
begin
......
fcontent:=VarArrayCreate([0, Stream.Size - 1], varByte);
p := VarArrayLock(fcontent);
try
Stream.Position := 0;
Stream.Read(p^, Stream.Size);
finally
VarArrayUnlock(fcontent);
end;
....
客户端
....
问题2：image类型的数据据我所知只有有这一种方法、
我可是现给你做出来的噢。：）
不会吧。我就是这样试验的，没错。
我把原码给你，你参考一下。
1。应用服务器：
procedure Tywh.SqlTest(var filename: WideString; out fcontent: OleVariant);
var str:string;
Stream:TMemoryStream;
P:pointer;
begin
Str:='SELECT filename, fcontent FROM filetable';
if query_tmp.Active then query_tmp.Close;
query_tmp.SQL.Clear;
query_tmp.SQL.Add(str);
try
query_tmp.Open;
if not query_tmp.Eof then
begin
while not query_tmp.Eof do
begin
if not query_tmp.FieldByName('fcontent').IsNull then
begin
//stream转换为OleVariant
stream:=TMemoryStream.Create;
FileName:=query_tmp.Fields[0].AsString;
TBlobField(query_tmp.FieldByName('fcontent')).SaveToStream(stream);
fcontent:=VarArrayCreate([0, Stream.Size - 1], varByte);
p := VarArrayLock(fcontent);
try
Stream.Position := 0;
Stream.Read(p^, Stream.Size);
finally
VarArrayUnlock(fcontent);
end;
break;
end
else query_tmp.Next;
end;
end;
except on e:exception do
FileName:=e.Message;
end;
end;
2.客户端：
procedure TForm1.Button1Click(Sender: TObject);
var filename:string;
fcontent:OleVariant;
fstream:tmemorystream;
p : Pointer;
tmpf:textfile;
i:integer;
j:tjpegimage;
begin
if not SocketConnection1.Connected then SocketConnection1.Open;
try
SocketConnection1.AppServer.Sqltest(filename,fcontent);
//OleVariant转换为stream，并把值传递给stream
fstream:=tmemorystream.Create;
//j:=tjpegimage.Create;
fStream.Position := 0;
i:=sizeof(fcontent);
fstream.Size:= VarArrayHighBound(fcontent,1)-VarArrayLowBound(fcontent,1)+1;
p := VarArrayLock(fcontent);
fStream.Write (p^, fStream.Size);
VarArrayUnlock (fcontent);
fstream.LoadFromStream(fStream);
fstream.SaveToFile('e:\kkk.txt');
//j.LoadFromStream(fstream);
//image.Picture.assign(j);
except on e:exception do
showmessage(e.Message);
end;
end;
这回应该不会再有错了吧
