Matlab + Java: java.lang.ExceptionInInitializerError when trying to use javabuilder

Question

Hello,

I've been trying to use Matlab's javabuilder package under Windows XP, but I'm getting a strange error when trying to instantiate any javabuilder class. To illustrate the problem, I've created a simple program that prints the MCRROOT and PATH system variables (to check if they're correctly set) and tries to create a MWCharArray:

import com.mathworks.toolbox.javabuilder.*;
import com.mathworks.toolbox.javabuilder.internal.MCRConfiguration;

class Main
{
   public static void main(String[] args)
   {
       System.out.println("MCRROOT: " + System.getenv("MCRROOT"));
       System.out.println("PATH: " + System.getenv("PATH"));
       System.out.println(MCRConfiguration.isInstalledMCR());
       MWCharArray test = new MWCharArray("Test");
   }
}

When I execute the program, the output is:

MCRROOT: C:\Program files\MATLAB\MATLAB Compiler Runtime\v710
PATH: C:\Program files\CollabNet Subversion Client;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\Program files\MATLAB\MATLAB Compiler Runtime\v710
false
Exception in thread "main" java.lang.ExceptionInInitializerError
        at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration.getMCRRoot(MCRConfiguration.java:77)
        at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration$ModuleDir.<clinit>(MCRConfiguration.java:51)
        at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration.getModuleDir(MCRConfiguration.java:56)
        at com.mathworks.toolbox.javabuilder.internal.MWMCR.<clinit>(MWMCR.java:1447)
        at com.mathworks.toolbox.javabuilder.MWUtil.GetUnknownClassID(MWUtil.java:1258)
        at com.mathworks.toolbox.javabuilder.MWClassID.<clinit>(MWClassID.java:41)
        at com.mathworks.toolbox.javabuilder.MWCharArray.<init>(MWCharArray.java:75)
        at Main.main(Main.java:11)
Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -1
        at java.lang.String.substring(String.java:1937)
        at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration$MCRRoot.get(MCRConfiguration.java:70)
        at com.mathworks.toolbox.javabuilder.internal.MCRConfiguration$MCRRoot.<clinit>(MCRConfiguration.java:72)
        ... 8 more
Java Result: 1

First of all, are MCRROOT's and PATH's values correct? I've tried google for finding out how to set MCRROOT, but there are conflicting results: some sources say that I should include de version dir, others say the opposite. Also, why is the isInstalledMCR method returning false? I've double-checked the MCR installation (and even uninstalled and installed it to be sure), so why isn't the library finding it?

Thanks on advance for any help!

Edit: I've also tried setting MCRROOT with no version string, and it also fails.

Answer 1

Just wild guessing! Java is messing around with strings, while your 'mcrroot' contains white spaces. I might change the mcr install path to something like C:\MATLAB\MATLABCompilerRuntime\v710, omitting any white spaces and special characters.

Answer 2

I've found the solution, so I'm post a self answer for future reference: Besides adding the javabuilder.jar to the program's classpath, you also have to add the path to the MCR's runtime libraries to the java.library.path JDK parameter.

My mistake was that, instead of setting the path as the path to the libraries at the MCR installation directory (On my case, C:\MATLAB\MCR\v710\runtime\win32), I copied the runtime directory to my project's dir and used it instead. It seems that the javabuilder library uses the java.library.path variable the guess the MCROOT, what would explain the weird "StringIndexOutOfBoundsException".