Develop Reference

Error: IllegalAccessError Java, when using another library's command in a library

Here is my Java library (.aar) file's code.
package com.sahib.ffpy;
import com.arthenica.ffmpegkit.FFmpegSession;
import com.arthenica.ffmpegkit.FFmpegKit;
public class ffpy<command>
{
public static void Run(final String command) {
final FFmpegSession session = FFmpegKit.execute(command);
}
}
This is supposed to take a command and execute in FFmpegKit by ARTHENICA.
I am using this library with pyjnius to run it as I can not directly do.
FFmpegSession session = FFmpegKit.execute(command)
In python.
This is how my python code looks:
FFMPEG = autoclass('com.sahib.ffpy.ffpy')
FFMPEG.Run("-i "+INPUT_FILE+" -qscale:v "+str(FRAME_QUALITY)+" TEMP/frame%06d.jpg -hide_banner")
I am using Kivy/Buildozer.
Here are the Gradle dependencies in buildozer:
android.add_aars = ffpy-debug.aar
android.gradle_dependencies = "com.arthenica:ffmpeg-kit-full:5.1"
I have tried extracting the classes.jar from both ffmpegkit and this and combining them, which throws a different error (I know it's not the right way to do it). I tried building ffmpegkit myself. I have tried directly using FFmpeg Kit in Python, but I don't think it will work.

GraalVM - embedding python multi-file project in java

I couldn't find a solution create a polyglot source out of multiple files in GraalVM.
What exactly I want to achieve:
I have a python project:
my-project:
.venv/
...libs
__main__.py
src/
__init__.py
Service.py
Example sourcecode:
# __main__.py
from src.Service import Service
lambda url: Service(url)
# src/Service.py
import requests
class Service:
def __init__(self, url):
self.url = url
def invoke(self):
return requests.get(self.url)
This is very simple example, where we've got an entry-point script, project is structured in packages and there is one external library (requests).
It works, when I run it from command-line with python3 __main__.py, but I can't get it work, when embedding it in Java (it can't resolve imports).
Example usage in java:
import org.graalvm.polyglot.Context;
import org.graalvm.polyglot.Source;
import org.graalvm.polyglot.Value;
import java.io.File;
import java.io.IOException;
public class Runner {
public static void main(String[] args) throws IOException {
Context context = Context.newBuilder("python")
.allowExperimentalOptions(true)
.allowAllAccess(true)
.allowIO(true)
.build();
try (context) {
// load lambda reference:
Value reference = context.eval(Source.newBuilder("python", new File("/path/to/my-project/__main__.py")).build());
// invoke lambda with `url` argument (returns `Service` object)
Value service = reference.execute("http://google.com");
// invoke `invoke` method of `Service` object and print response
System.out.println("Response: " + service.getMember("invoke").execute());
}
}
}
It fails with Exception in thread "main" ModuleNotFoundError: No module named 'src'.
The solution works for javascript project (having similar index.js to __main__.py, its able to resolve imports - GraalVM "sees" other project's files, but somehow it doesn't, when using python.
I found out, that python is able to run zip package with project inside, but this also doesn't work with GraalVM.
Is there any chance to accomplish it? If not, maybe there is a similar tool to webpack for python (if I could create a single-file bundle, it should also work).
Btw, I don't know python at all, so I may missing something.
Thanks for any help!

a very simple case does not write pdf file by using itext in IBM i

i'm trying to use itext (5.5.13) in IBM i (AKA iseries, Power, long ago AS/400). It could be done embedding java code into RPG ILE procedures, or executing plain java. We use Apache POI for Excel for a while, and it works well. We are testing itext now, but some issue persist yet.
Given that, I'm trying to test itext in plain java into IBM i. I prepared a very simple example, taken from listing 1.1 of "Itext in action", and run it. It seems to work well, but nothing is generated. No pdf file results. And no error appears while running.
am i forgetting something? are there some other aspects to take in account?
here is the code:
package QOpenSys.CONSUM.Testjeu;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.PdfWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
public class test1{
public static final String filePdf = "/QOpenSys/MyFolder/Testjeu/PdfRead1.pdf";
public static void main(String[] args)
throws DocumentException, IOException
{
///QOpenSys/MyFolder/Test/WrkBookRead1.pdf
//pdfDocument = new_DocumentVoid()
Document pdfDocument = new Document();
//pdfWriter = get_PdfWriter( pdfDocument: pdfFilePath);
PdfWriter.getInstance(pdfDocument, new FileOutputStream( filePdf ));
// jItxDocumentOpen( pdfDocument );
pdfDocument.open();
//pdfParagraph = new_PdfParagraphStr( PhraseString );
Paragraph jItxParagraph = new Paragraph("Hola, pdf");
//addToDocPg = jItxDocumentAddParagraph( pdfDocument: pdfParagraph );
pdfDocument.add(jItxParagraph);
//jItxDocumentClose( pdfDocument );
pdfDocument.close();
}
}

Solved. As said before, there was a first issue: it seems java function ran well because not errors/warnings were visible at qshell. It was false: errors were sent to outq, and were available at spool file. Being reviewed, it was a simple classpath issue. It required a full day to figure out what failed locating classpath.
Now it works, and pdf is created. I ran it on qshell, declaring environment variables for java_home (three jvm are executed concurrently by several applications), for classpath, and a couple required for tracing. Classpath declares first my class and secondly itext classes. Remaining classes comes from JRE. I have a full list of classes loaded by class loader. I hope it will help to find what fails in our embedded RPG ILE call to itext.

Is it possible to convert this Java code to Jython for a Minecraft Plugin?

I was looking at this video to find some information on making Minecraft Plugins. https://youtu.be/r4W4drYdb4Q
All plugins are made with Java. Since I program with Python I was wondering if it is possible to make a Plugin similar to the one seen in the video but with Jython. I am not sure if this is possible but I started trying.
When programming Java most people use Eclipse and there is a button that says "Add external Jar" and that is where you input the spigot jar file. From what I understand I can do that with:
import sys
sys.path.append("spigot-1.15.2.jar")
in Jython. Then there comes the tricky part. How would I go about converting this:
Code Part 1
Code Part 2
From what I thought I needed to do was something like:
from org.bukkit.plugin.java import JavaPlugin
class Main(JavaPlugin):
def onEnable():
pass
#what do I put here?
def onDisable():
pass
#what do I put here?
But I don't think I am properly converting the Java code to Jython. What would be the proper way to convert the code from Java to Jython?
Thanks very much!

From my understanding you want to interact from your Jython code with a Java class which extends JavaPlugin.
For this I suggest you write a thin wrapper in Java which then calls your Jython code where you do the heavy lifting in your familiar language. A skeleton of the wrapper could look like this:
package {$GroupName}.{$ArtifactName};
import org.bukkit.plugin.java.JavaPlugin;
import org.python.util.PythonInterpreter;
public final class {$ArtifactName} extends JavaPlugin {
#Override
public void onEnable() {
PythonInterpreter pi = new PythonInterpreter();
pi.execfile("enable.py"); // enable.py is the Jython file with the enable stuff
}
#Override
public void onDisable() {
PythonInterpreter pi = new PythonInterpreter();
pi.execfile("disable.py"); // enable.py is the Jython file with the disable stuff
}
}
Be aware that instantiating PythonInterpreter is rather slow, so you'd be better off with a pattern where you do this only once. Plus then you can share data between enable and disable!
For more details and other options (like having the Jython stuff in one file and calling into it via pi.exec) look at Chapter 10: Jython and Java Integration in the Jython Book.
Also keep in mind when coding away: Jython is only Python 2.7!!!

InOut.readInt() only working in Windows Java Editor

At school, I write Java programs with Windows’ Java Editor (console mode). There, InOut.readInt() (used for user input) works without problems and I don’t have to import anything.
Now, I have a Java homework for the holidays, and I try to write Java programs on my Mac. In online console Java editors, the line InOut.readInt() causes this error:
/IntBetween10And100.java:8: error: cannot find symbol
int input = InOut.readInt("Integer --> ");
^
symbol: variable InOut
location: class IntBetween10And100
1 error
I already tried import lines (placed before the class) like:
import java.*
import java.util.*
import java.util.InOut
import java.io.BufferedStreamReader
import java.util.*;
public class IntBetween10And100 {
public static void main(String args[]) {
int input = InOut.readInt("Integer --> ");
}
}
int input = InOut.readInt("Integer --> ");
should produce the line
Integer -->
but instead, the error message (seen above) appears.

OK, so you are using the "Java-Editor" tool on Windows for writing your Java code.
It turns out that Java-Editor includes a class called InOut as an example class. (You can see it here: http://javaeditor.org/doku.php?id=en:examples).
For various reasons, it is not suitable for use in production code of any kind:
It is not part of the Java SE class library, or any 3rd-party libraries.
It is a class in the default package
It has limited functionality, even compared to the real System.in and System.out
It would interfere with any application or 3rd party library code that uses System.in in the normal way. (It creates its own BufferedReader to wrap System.in. That is liable to capture "type-ahead" input.)
You don't really need to use it for educational purposes either. It is only a wrapper class ...
However, if you want to use InOut outside of the Java-Editor context, you could simply download the source code from the page above and add it to your project. I can't tell you exactly how, but adding classes should be explained in the documentation of the tool you are using now! (If you are serious about learning Java, I would actually recommend that you download and install a real Java JDK and a real Java IDE on your own computer.)
The authors have neglected to include an explicit copyright notice in the InOut.java file. However, the Java-Editor site as a whole is licensed as "CC Attribution-Share Alike 4.0 International".