[英]Delphi datasnap send an from image to server (to be stored in database)
我在上下搜索了一個可行的解決方案,以使用datasnap方法將圖像(例如tpngimage)發送到服務器-但我無法使其正常工作。
當我加載圖像並將其保存到內存流時,我能夠從流中讀取圖像-在客戶端本地,這並不奇怪。 但是,當調用服務器方法時,流為nil並且不包含任何內容,其他參數也很好(簡單的數據類型和對象)。
我想念這里明顯的東西嗎? 我的印象是TStream是datasnap方法的有效數據類型,但也許我錯了嗎?
來自客戶端的看起來像這樣。
function TPerson.Update: Boolean;
var
AStream : TMemoryStream;
APicture : TPngImage;
ASize : Integer;
begin
if (FId > 0) then // if Id below zero we have a problem
begin
ClientModule1.ServerMethods1Client.UpdatePerson(Self);
APicture := TPngImage.Create;
AStream := TMemoryStream.Create;
try
// Temp just use a file
AStream.LoadFromFile('.\images\075.png');
ASize := AStream.Size;
AStream.Position := 0; // wind back if needed
// just for testing, we can read back the image from the stream
APicture.LoadFromStream(AStream);
ClientModule1.ServerMethods1Client.UpdatePersonPicture(self, ASize, AStream);
finally
FreeAndNil(AStream);
FreeAndNil(APicture);
end;
end;
FModified := False;
end;
和代理方法看起來像這樣
procedure TServerMethods1Client.UpdatePersonPicture(APerson: TPerson; ASize: Integer; APictureStream: TMemoryStream);
begin
if FUpdatePersonPictureCommand = nil then
begin
FUpdatePersonPictureCommand := FDBXConnection.CreateCommand;
FUpdatePersonPictureCommand.CommandType := TDBXCommandTypes.DSServerMethod;
FUpdatePersonPictureCommand.Text := 'TServerMethods1.UpdatePersonPicture';
FUpdatePersonPictureCommand.Prepare;
end;
if not Assigned(APerson) then
FUpdatePersonPictureCommand.Parameters[0].Value.SetNull
else
begin
FMarshal := TDBXClientCommand(FUpdatePersonPictureCommand.Parameters[0].ConnectionHandler).GetJSONMarshaler;
try
FUpdatePersonPictureCommand.Parameters[0].Value.SetJSONValue(FMarshal.Marshal(APerson), True);
if FInstanceOwner then
APerson.Free
finally
FreeAndNil(FMarshal)
end
end;
FUpdatePersonPictureCommand.Parameters[1].Value.SetInt32(ASize);
FUpdatePersonPictureCommand.Parameters[2].Value.SetStream(APictureStream, FInstanceOwner);
FUpdatePersonPictureCommand.ExecuteUpdate;
end;
Server方法如下所示-由於APictureStream為nil,因此失敗。
procedure TServerMethods1.UpdatePersonPicture(APerson: TPerson; ASize: integer;
APictureStream: TMemoryStream);
var
APicture : TPngImage;
begin
fdqPersons.Close;
fdqPersons.SQL.Clear;
fdqPersons.Connection.StartTransaction;
try
fdqPersons.SQL.Add('update Persons set Picture=:Picture ');
fdqPersons.SQL.Add('where Id=:Id');
fdqPersons.ParamByName('Id').Value := APerson.Id;
APicture := TPngImage.Create;
try
// APicture for testing - but APictureStream is nil!
APicture.LoadFromStream(APictureStream);
fdqPersons.ParamByName('Picture').Assign(APicture);
fdqPersons.ExecSQL;
finally
FreeAndNil(APicture);
end;
fdqPersons.Close;
fdqPersons.Connection.Commit;
LogEvent(format('Person picture updated ID: %d',[APerson.id]));
except
on e:exception do
begin
fdqPersons.Connection.Rollback;
LogEvent(format('Error updating person picture %s',[e.Message]));
raise;
end;
end;
end;
當您調用APicture.LoadFromStream(AStream);
流的位置移到最后,因此,當將其傳遞到ClientModule1
它沒有任何要讀取的數據。 擺脫不必要的部分,將流寫入TPngImage
或在該部分之后將流的位置重置為0。
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