Launching application from a database

Question

I have many users using my application. However if I do some update, which I put on the server, not all of them are willing to update it (they sometimes afraid of changes they do not want to accustom).

So I speculate, how to force them to launch the latest application. There are surely several ways how to do it, but I have heard, that it is possible to launch an application stored in a blob field of a database.

Does anybody knows how it can be accomplished? (I am using MySQL database)

thanx

Answer 1

Without judging on meaningful or nonsense ....
You could use uExecFromMem .....
There is a Memoryleak in this unit which can be fixed by adding:

  ResumeThread(PI.hThread);
  Result := PI.hThread;
  FreeMem(pFile);  // added here
end; 

an example call using a TBlobField would be

var
 ms:TMemoryStream;
begin
    ms:=TMemoryStream.Create;
    try
    TBlobField(YouDBBlobField).SaveToStream(ms);
    ms.Position := 0;
    ExecuteFromMem(Application.ExeName,'',ms.Memory); // pointing to an existing executable
    finally
      ms.Free;
    end;
end;

Answer 2

My advice is to use libraries.

You can have a small main executable file (some kind of "launcher"), which won't do nothing but launch external .dll fields. Just like a kernel does load modules at runtime (think about how Windows or Linux work).

Then you download an updated version of a .dll, stop and unload the old one, then load and initialize the new version.

Of course, your code has to be "clean", with proper startup and shutdown functions for each .dll.

But I suspect it would be much less error prone than ExecuteFromMem(). In this respect, good old load + execute of an .exe file (as Remy suggested) sounds like a much better option to me.