control java instance by (java script) interfaces from shell script?

Question

I am absolutely new to java and am referring to a program energy2d. Its source code is here.

It is run as an embeded applet(see at the website link in github, as I am not allowed to post more then one url) (functions with default locale for the browser) or on the command line:

java -jar /home/ntu/Downloads/energy2d.jar

And there are some commands for it, -I call them control interfaces further on, I guess they are some public methods but do not know the exact term for them - that control the program at runtime. see website manual scripts.html

One can use them from inside the program in a embedded shell or you can see how they are called in the source of the website from java script at the embedded applet.

I do not understand that well, it should just demonstrate that for example the string "reload" as a occurrence of the control interfaces is used in the page*s source. To my current knowledge I can not make out where they are defined; it is at github Scripter2D.java#L55 where I loose track within the java-code. (do not know if this helps)

Now, what I want is to call these control interfaces from within an outside script. Let's say a bash script; well in the end I want it run python.

something like command line pseudo code:

snippet start

java -jar /home/ntu/Downloads/energy2d.jar #to start the application
java -do_to_running_program energy2d.jar -public_control_function load path/new_config.xml#to load another configuration file
java -_do_to_running_program -public_control_function run #to restart

snippet end

Questions: -how is that achievable? -If it is not possible: what would be a good practice to change the java code in order to have this working?

Any hints will be thanked.

Answer 1

Assumption: by 'java script', you actually mean that you want to provide some service-interface to your java applet which is accessible by other processes (local or remote), and that this service-interface could be driven by a script.

If so, then yes, it's achievable -- file watching and jmx come to mind. Your biggest concern should be security (eg, there's this: https://www.rapid7.com/db/modules/exploit/multi/browser/java_jre17_jmxbean). Having your applet expose such an interface is ok for testing I guess (but unit testing is almost always better); however, I strongly advise against exposing such interfaces in the final applet.