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From "Peter Crowther" <Peter.Crowt...@melandra.com>
Subject RE: Advice about Tomcat on x86_64 architecture..
Date Wed, 17 Oct 2007 15:46:10 GMT
> From: Swapnil.Kale [mailto:swapnil.kale@gmail.com] 
> I tried installing tomcat 32 bit on a 64 bit JVM but it didnt work.

That is very unexpected.  *Tomcat* is pure Java.  I can do a file copy
of my entire Tomcat installation and my apps from my 32-bit development
box to my 64-bit staging box (and back again) and Tomcat starts and runs
without error.  Note that I'm using the zip download and starting it
from the batch file; I do *not* install a Windows service, and I do
*not* use any native libraries.

> 1) Can i host 32 bit compiled war file on 64 bit Tomcat / JVM ? <If my
> tomcat installation succeeds>

Yes.  I do this regularly.  The bytecodes emitted by the compiler are
identical whether the compiler runs on a virtual machine on a 32-bit,
64-bit, 36-bit or any other physical hardware.

> 2) What if i recompile the war on 64 bit jvm and host it on 
> 64 bit Tomcat?

Yes.  I do this more rarely (my dev box is my usual compile
environment), but it works.  I repeat: the bytecodes emitted by the
compiler are identical whether the compiler runs on a virtual machine on
a 32-bit, 64-bit, 36-bit or any other physical hardware.

> I've read that the size of the primitive datatypes in 64 bit 
> is different,
Whoever wrote that is wrong.  Java is not C.  Java primitive sizes are
standard, regardless of the physical machine.

> so if i use Java web start and launch the application from 
> remote machine
> <32 bit> using JNLP, will it work on that 32 bit machine? 
> having 64 bit machine compiled jars?

Yes.

> If I host the 32 bit compiled war on 64 bit Tomcat / 64 bit JVM,
> What am i gonna miss/gain? except the lot of heap memory

Nothing.

> The picture is still not clear, Can you throw some light on this?

The correct Java virtual machine must be installed for the operating
system and hardware.

Java bytecode in .class, .jar and .war files is portable.  Tomcat is
portable.

Native code is not portable.  The code for installing Tomcat as a
Windows service is not portable.

If you have installed Tomcat from something other than the zip file (or
the .tar.gz file) on the Apache Tomcat site, you may have some native
code that you were not expecting.  Install from the zip file, start
Tomcat via startup.bat and see whether the problem is still there.

		- Peter

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