JLink error

[cynthia wu]

I created a jar file that runs methods that I have created in
Mathematica. The java file has everything(libraries, import) it needs
to connect to the Mathematica Kernel and run the methods.

My issue is that I am using my jar file in Ruby. I have imported the
jlink library, my jar file, and everything else I feel it needs to run
my java file. However, I am getting the current error:

Fatal error: cannot find the required native library named
JLinkNativeLibrary.dll

Any suggestions would be greatly appreciated.

[David Bailey]

JLink communicates with Mathematica via MathLink, which is in a native
library (C) - so the error makes perfect sense.

Are you writing Java code that will invoke Mathematica code, or are you
writing Java code that will be called from Mathematica in the first
instance? What do you intend to happen with Ruby - do you intend Ruby to
call Java that then calls Mathematica?

Note that if you invoke Java from within mathematica, you will be using
Java 6 (with Mathematica 7) with a large class path that you can
discover using

GetClassPath[]

You obviously need some items from that path.

I hope this at least gives you a few thoughts to follow up on.

David Bailey
http://www.dbaileyconsultancy.co.uk

[Patrick Scheibe]

Hi,

the JLink uses MathLink which is a C-Library and the only real link to
Mathematica. Everthing in Java seems to use this connection.
When you start to use JLink it loads this JLinkNativeLibrary.dll library
through JNI, the java native interface
(http://en.wikipedia.org/wiki/Java_Native_Interface) and this step
obviously fails.

You can have a look at the sources if it helps to understand. It is
under

MathematicaRootPath/SystemFiles/Links/JLink/Source/Java/com/wolfram/jlink

in the file NativeLink.java.
What you have to do is to find out why java doesn't find this library
when it starts. You have this dll under the above mentioned path

/usr/local/Wolfram/Mathematica/7.0/SystemFiles/Links/JLink/SystemFiles/Libraries

but it should be installed globaly anyway.
This is the plan and the information I can provide. The rest is up to
you since it is hard to guess what's wrong from here.

Maybe you should try first to place the JLinkNativeLibrary.dll directly
into the directory of your application if you use Windoze.

Good Look.

Cheers
Patrick