Using RMI to synchronize two databases

Question

Hello
I have studied Java for some time, but never had
the opportunity to work in a "real project", but
now I have something to do...
I have the following situation: two offices
of a company, the central one running SQL Server
database and other running Oracle, must change
information, reading data from Oracle and saving in
SQLServer and vice-versa. The programs should be
running all day, checking at specified periods of
time if there is some information to be updated
in any database.
The offices are phisically far, so it should be
used Internet to make the connection (both sites
are connected to Internet 24h).
I was wondering on using the Java RMI technology
to achieve this. I have read the official Sun
documentation about RMI and some articles, and I
found it very interesting, and pretty easy to
implement.
But I have some "real world" questions:
- Is RMI the ideal solution for this problem, or
there is some newer or more adequate one?
- At first it would be a small amount of data
to be synchronized, but if it grows a lot or
more offices are to be connected, is RMI performance
good? (is it quick?)
- About security - is RMI secure? I mean, I think
the server program should be listening a port in a
IP address open to ALL the internet... How safe is
the user authentication, or this is responsability of
the application?
- What is the relationship between RMI and proxies,
firewalls etc? Are they compatible?
- XML is something to think about using for this
application, or it have nothing to do to the job?
The initial option was using a Microsoft solution
to make this application :(, but I would be very happy
if I could use Java ;) , but I have to have the
adequate technical base to suggest it...
So, any help would be very welcome!
Luis Cabral

Answer 1

Here's a set of (some) answers based on my experience (which is NOT synchronizing two databases, but on synchronizing sets of files across a tree of file servers.)
Hello
1. It sounds like two databases must be cross-synchronized. You didn't say what the platforms were, but if they are mixed, then java is a positive choice.
2. Java rmi is fine for doing this kind of work. However I can't give you any performance guarantees. You probably need to get some fine requirements and write some model programs.
3. YOU are responsible for security. RMI gives you connectability; you have to develop some kind of cross-authentication procedure as part of you application.
4. To work over the internet, you will have to develop some way through firewalls.
o If the two sites use "Virtual private networks", then both the security issue and the firewall issue are mostly solved for you.
o Otherwise, and maybe even with vpn, you will have to do a little bit of work to use fixed port numbers. (The way rmi works is that there is a listener at a fixed port which will let a remote program "look up" a local object; after that, communication takes place object-object over a randomly-assigned port.) It takes about a dozen lines of code to make this work.
5. I don't think XML has anything to do with this problem. It MAY help you if you have serious data conversion issues. I hear it's a pig.
Finally, an application item that may or may not be an issue: Two databases, two platforms == possible character set conversion problems.