ExceptionInInitializerError / InaccessibleObjectException: Unable to make field private final java.util.Comparator java.util.TreeMap.comparator accessible: module java.base does not "opens java.util" to unnamed module @5cde6747

[msingh2890]

I am working on a tool that would take dmn files from Signavio and use drools engine to process inputs on that. While trying to set up this repository locally, I am getting the following error(which usually comes up when we are using wrong versions of JDK or incompatible versions of some dependency but I see that java version has been set to 1.8 in pom.xml file).
=== DMN EXECUTION === 2023-08-08 05:43:30,602 [main] INFO Found kmodule: file:/C:/Users/msinghchoudhary/Documents/jpmc/signavio_github/dmn-and-drools-execution-examples/target/classes/META-INF/kmodule.xml Exception in thread "main" java.lang.ExceptionInInitializerError at com.thoughtworks.xstream.XStream.setupConverters(XStream.java:990) at com.thoughtworks.xstream.XStream.<init>(XStream.java:593) at com.thoughtworks.xstream.XStream.<init>(XStream.java:515) at com.thoughtworks.xstream.XStream.<init>(XStream.java:484) at com.thoughtworks.xstream.XStream.<init>(XStream.java:430) at com.thoughtworks.xstream.XStream.<init>(XStream.java:397) at org.kie.soup.xstream.XStreamUtils.createTrustingXStream(XStreamUtils.java:120) at org.drools.compiler.kproject.models.KieModuleMarshaller.<init>(KieModuleMarshaller.java:46) at org.drools.compiler.kproject.models.KieModuleMarshaller.<clinit>(KieModuleMarshaller.java:44) at org.drools.compiler.kproject.models.KieModuleModelImpl.fromXML(KieModuleModelImpl.java:151) at org.drools.compiler.kie.builder.impl.ClasspathKieProject.fetchKModule(ClasspathKieProject.java:203) at org.drools.compiler.kie.builder.impl.ClasspathKieProject.fetchKModule(ClasspathKieProject.java:165) at org.drools.compiler.kie.builder.impl.ClasspathKieProject.discoverKieModules(ClasspathKieProject.java:133) at org.drools.compiler.kie.builder.impl.ClasspathKieProject.init(ClasspathKieProject.java:97) at org.drools.compiler.kie.builder.impl.KieContainerImpl.<init>(KieContainerImpl.java:138) at org.drools.compiler.kie.builder.impl.KieContainerImpl.<init>(KieContainerImpl.java:148) at org.drools.compiler.kie.builder.impl.KieServicesImpl.newKieClasspathContainer(KieServicesImpl.java:140) at org.drools.compiler.kie.builder.impl.KieServicesImpl.newKieClasspathContainer(KieServicesImpl.java:130) at org.drools.compiler.kie.builder.impl.KieServicesImpl.getKieClasspathContainer(KieServicesImpl.java:101) at org.drools.compiler.kie.builder.impl.KieServicesImpl.getKieClasspathContainer(KieServicesImpl.java:79) at com.signavio.examples.dmn.AbstractDmnExample.createDmnRuntime(AbstractDmnExample.java:47) at com.signavio.examples.dmn.AbstractDmnExample.<init>(AbstractDmnExample.java:36) at com.signavio.examples.dmn.SimpleDmnExample.<init>(SimpleDmnExample.java:29) at com.signavio.examples.SignavioExamples.executeDmnExamples(SignavioExamples.java:40) at com.signavio.examples.SignavioExamples.main(SignavioExamples.java:33) Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make field private final java.util.Comparator java.util.TreeMap.comparator accessible: module java.base does not "opens java.util" to unnamed module @5cde6747 at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354) at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297) at java.base/java.lang.reflect.Field.checkCanSetAccessible(Field.java:178) at java.base/java.lang.reflect.Field.setAccessible(Field.java:172) at com.thoughtworks.xstream.core.util.Fields.locate(Fields.java:40) at com.thoughtworks.xstream.converters.collections.TreeMapConverter.<clinit>(TreeMapConverter.java:50) ... 25 more
Before moving to this approach(using this repo) I had been using drools kie/dmn apis and had ~45% incorrect responses, and had no support for custom functions but I was able to get it to run, unlike this one. I would really appreciate any help whatsoever in setting this up.

[msingh2890]

@j-beyer @TommyNeubert @Jonas-Heinrich @tsologub : Would really appreciate the help. Please take a look

[msingh2890]

RESOLVED: The pom.xml sets jdk version to 1.8, but the local jdk version for eclipse was a higher version, changing it made it work.