1.19.2 Error with jython-standalone in a Forge mod 1.19.2

[Rfailes Dev]

Hello, Im trying to use PythonInterpreter from "jython-standalone" library in my Forge mod.

I want to run Python scripts from Java code using Jython. I have added the dependency for jython-standalone in my build.gradle file, but I still get a "NoClassDefFoundError" when I try to use PythonInterpreter.

Intellij IDEA does not show any errors in the editor, but the error occurs at runtime. I have tried to sync, rebuild, and invalidate caches, but nothing works.

Here is the part of my build.gradle file:
 

dependencies {
    minecraft 'net.minecraftforge:forge:1.19.2-43.2.4'
    implementation 'org.python:jython-standalone:2.7.3'
}

The error:
 

Exception in thread "Thread-11" java.lang.NoClassDefFoundError: org/python/util/PythonInterpreter

The part of code:
 

import org.python.util.PythonInterpreter;

public class p1 {
    public static void LoadPart() {
		PythonInterpreter interpreter = new PythonInterpreter();
...other

I have searched for a solution, but I could not find anything that works for me.
what im doing wrong?(Mb I imported this wrong?)

[warjort]

8 hours ago, Rfailes Dev said:

I have searched for a solution, but I could not find anything that works for me.

what im doing wrong?(Mb I imported this wrong?)

But you didn't search this forum. Because this question has been asked many times before.

 

Adding a gradle dependency will make the jar available at compilet time but it won't load the jar into forge.

Forge will only load jars that are mods.

You need to turn that jar into a mod.

Or include that jar within your mod. Either using https://forge.gemwire.uk/wiki/Jar-in-Jar or as mentioned on that link use one of the gradle plugins that does shading/creates "uber jars".

 

e.g. this is the create mod using jarInJar

https://github.com/Creators-of-Create/Create/blob/a41053b8966edf7bd9732223b18f783fdb52521d/build.gradle#L168

[Rfailes Dev]

I do something like this:

dependencies { 
    minecraft 'net.minecraftforge:forge:1.19.2-43.2.4'
    jarJar(group: 'org.python', name: 'jython-standalone', version: '[2.7.3,)')     
    implementation fg.deobf('org.python:jython-standalone:2.7.3')

But it still giving the error:

Exception message: java.lang.ClassNotFoundException: org.python.util.PythonInterpreter

 

[warjort]

If you want help you need to post more than snippets out of context.

Put something on github so we can see the whole thing.

 

But I guess you didn't actually read the documentation.

Quote

Jar-In-Jar is a completely optional system. To enable it, you need to call `jarJar.enable()`

https://github.com/Creators-of-Create/Create/blob/a41053b8966edf7bd9732223b18f783fdb52521d/build.gradle#L25

 

There maybe other you things you need to do depending upon what jar you include and its dependencies. Again read the docs.

 

Also

Quote

implementation fg.deobf('org.python:jython-standalone:2.7.3')

this says forge should deofuscate that jar. But since it is not a minecraft mod (unlike the examples from create) there is no need to do that.

This is the main wiki guide for dependencies, but you should also read the main gradle docs.

https://forge.gemwire.uk/wiki/Dependencies

 

All these issues have been discussed many many times before in this forum.

Please try to use the search function instead of posting repeat questions.

[warjort]

For completeness (in case somebody does use search in future and finds this thread):

If you can't get jarInJar to work, you can always try shading, e.g.

https://imperceptiblethoughts.com/shadow/introduction/

this is the old method people used before jarInJar and is still commonly used.

 

Or you can fork that jython project to add a META-INF/mods.toml to it which will turn the jar into a mod.

https://docs.minecraftforge.net/en/latest/gettingstarted/modfiles/

e.g. this is how this mod adds javascript support to minecraft by forking mozilla's rhino

https://github.com/KubeJS-Mods/Rhino

[warjort]

Example of the spark mod using shading (including package renaming to avoid conflicts in case other mods do the same thing with the same jar):

https://github.com/lucko/spark/blob/87512b5eeffe8a0d3cacb08f9a98d513fb87dbfd/spark-forge/build.gradle

Edited January 4, 2024 by warjort

[Rfailes Dev]

Thank you very much for your help.

I am not at my computer right now, but I will try these methods as soon as I can.
I just needed python in my java mod to be able to execute some simple algorithms dynamically by loading them from a file.

Thank you