Best way to override MATLAB's default static javaclasspath

Question

MATLAB is configured to search its static java class path before searching the user-modifiable dynamic path. Unfortunately, the static path contains quite a number of very old p

Answer 1

Instead of obfuscating the package as suggested by @user2443532, I have found it easier to "shade" the conflicting package instead of obfuscating it - unless you actually need obfuscation. One easy way to do this is to build your package using Maven and use the maven-shade-plugin. Internal calls are modified automatically, so you don't need to modify any of the Java code.

Direct calls from Matlab will need to be modified - for example, calls to com.opensource.Class become shaded.com.opensource.Class.

For more info on shading, see What is the maven-shade-plugin used for, and why would you want to relocate Java packages?

Answer 2

If you're distributing a jar that's intended to be used with matlab, it may be better to use proguard as described at http://code.google.com/p/guava-libraries/wiki/UsingProGuardWithGuava.

If you specify that all of your classes and their (public) fields and methods are to be preserved and include guava as a program jar (not a library), then it will rename all of guava's methods and update your compiled bytecode to reference the new names.

It seems a bit hackish, but depending on the audience, it may be significantly easier than teaching your users about static vs. dynamic classpath, and it won't break any matlab code that depends on the old behavior.

Answer 3

One hack that appears to work is to add the jar to the top of the classpath.txt file that can be found in your MATLAB installations toolbox/local folder. Unfortunately, this is automatically generated and may get rewritten at some unspecified time, such as when you install new toolboxes, so this approach would require you to have some way to notice when this happens and reapply the hack.

Answer 4

I got an official response from Mathworks:

As of MATLAB R2013a (also in R2012b), classes can be added to the front of the static Java class path by including the following line in javaclasspath.txt:

<before>

Any directory that is after this line in javaclasspath.txt will be added to the front of the static Java class path. This is an undocumented use of javaclasspath.txt as of R2013a.

But overall in MATLAB, the ability to add classes to the front of the static Java classpath is not available through javaclasspath.txt in MATLAB 8.0 (R2012b).

MATLAB searches for classpath.txt in the following order:

1. In the startup directory. As of MATLAB 8.0 (R2012b) a warning will be shown if the file is found there and it will be ignored.

2. In the first directory on the MATLABPATH environment variable. (This environment variable is used in the bin/matlab shell script on Linux and in general is not used by the end-user).

3. In the toolbox/local directory.

Although the MATLABPATH environment variable of point 2 is normally not used by end-users we can use it in a workaround to allow reading a custom classpath.txt outside of the toolbox/local directory.

On Windows:

You will need to create the MATLABPATH environment variable. The first directory on it should be your directory with the custom classpath.txt AND you will also need to add the toolbox\local directory as second option. So from a cmd prompt you could do:

set MATLABPATH=c:\Users\user\Documents\myMATLABClasspath;c:\Program Files\MATLAB\R2012b \toolbox\local matlab.exe