How to get the path to the executable when using launch4j?

You might add to your launch4j configuration

...
<jre>
...
<opt>-Djna.library.path="%EXEDIR%\\path\\to\\lib"</opt>
<opt>-Djava.library.path="%EXEDIR%\\path\\to\\lib"</opt>
...
</jre>
...

If you need more then a you might seperate several paths by a semikolon as usual.

< opt> Optional, accepts everything you would normally pass to java/javaw launcher: assertion options, system properties and X options. Here you can map environment and special variables EXEDIR (exe's runtime directory), EXEFILE (exe's runtime full file path) to system properties. All variable references must be surrounded with percentage signs and quoted.

Source: http://launch4j.sourceforge.net/docs.html

Set -Djna.library.path=<relative path of native libraries> (if using JNA) and -Djava.library.path=<relative path of native libraries>.

Alternatively, this can be done in Java code as: System.setProperty("jna.library.path","<relative path of native libraries>") and System.setProperty("java.library.path","<relative path of native libraries>"). You can append as many paths to refer to. In Windows, use ; to separate the paths.

This setup only has its effect on the JVM runtime of that Java application (not globally like LD_LIBRARY_PATH in Linux.)

Or, you can put this in Launch4J JVM options list under JRE tab. This is what I do in my projects.