🚀 go-pugleaf

Hey Glenn,

Your question is a longie, and a toughie.  I hoped someone would leap to
answer it.  Since not, I will pose an answer.  This is likely to inspire all
sorts of responses from the peanut gallery though.

1. Is there any reason to use any COM/DCOM at all?

Possibly, if you want to use the large collection of pre-existing COM
objects in your programs, then yes.  Microsoft claims that the entire OS,
and all system resources will be COM objects starting with NT 5.0, and
onward.  Drawbacks?  Yes.  You'll be limiting yourself to the Windows
platform.  Conversely, making your Java classes COM objects, will allow them
to be used by a variety of tools, and languages.

2. Is there an advantage to using RMI?

Possibly,  the RMI interface for Java code is as simple to use as for COM
when importing objects.  Implementing component objects is MUCH more
difficult in COM, than RMI.  RMI is platform independent, however, RMI works
only Java-to-Java, unlike COM, or for that matter CORBA.

3. If we used COM then does that mean that all the JAva classes need to be
run through the ActiveX Wizard for Java from Microsoft to create TLB's.

No.  Certainly you can create, customize, and bind your own TLBs, that's how
I do it.

4. How do those TLB's get accessed then from other Java classes so that COM
is the interface between them?  Or is that just a totally stupid thing to
do?  Should they all just use RMI?  Dio the all get run through JAVAREG or
JActiveX from Microsoft? Then how are they called?

Access the TLBs of Java/COM objects, starts with the system registry.  The
objects must be installed.  This is hard to summarize in a short answer.
The Visual J++ documentation provides good examples.  It is not difficult.

5.  How does Microsoft support RMI?  Or do they even have to for me to use
it on WinNT?

Microsoft is not excited to support RMI.  They feel it is too competitive
with COM.  However, RMI support for explorer is available from the Microsoft
site, in the unsupported libraries area.  This does mean however, that all
users of your applets must also download, and install this library too,
bummer.

6.  Is the only advantage to using DCOM over RMI the fact that there is MTS?

Not at all.  DCOM allows objects written in any language, including Java,
to interoperate over the network.  There is an increasing number of DCOM
objects being produced, as the number of non-Java programmers greatly
outnumber the rest of us.  (Hopefully not for long!)  DCOM operates most
efficiently with the OS, so when performance is critical, this may be your
only option.


Where do I sit in all this confusion?  There is no clear winner.  I use both
RMI, and
(D)COM.  I have not used CORBA, but it looks like multi-platform COM.  If
you are starting from scratch I would recommend the following:

   If the communications are Java to Java only, go with RMI.
   If the communications are Microsoft only, with non-Java components use
DCOM.
   If the communications are across multiple OSes, with some non-Java, use
CORBA.

Good Luck,

John