Problem of TreeSet/TreeMap

[urn1ce]

if you deserialize of TreeSet/TreeMap at java17 like this

package ...;

import com.thoughtworks.xstream.XStream;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.TreeSet;

public class XStreamTest {
    public static class MComparator implements Comparator<Object>{
        @Override
        public int compare(Object o1, Object o2) {
            return o1.toString().compareTo(o2.toString());
        }
    }
    public static void main(String[] args) {
        var ts = new TreeSet<Object>(new MComparator());
        var al = new ArrayList<Object>();
        al.add("ABC");
        ts.add(al);
        var xs = new XStream();
        xs.allowTypesByWildcard(new String[]{"**"});
        var str = xs.toXML(ts);
        System.out.println(str);
        var obj = xs.fromXML(str);//TreeMap has the same problem
        System.out.println(obj);
    }
}

you will see error

<sorted-set>
  <comparator class="xxxxx.XStreamTest$MComparator"/>
  <list>
    <string>ABC</string>
  </list>
</sorted-set>
Exception in thread "main" java.lang.ExceptionInInitializerError
    at com.thoughtworks.xstream.converters.collections.TreeSetConverter.unmarshal(TreeSetConverter.java:62)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:74)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:72)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:68)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:52)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:136)
    at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1464)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1441)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:1321)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:1312)
    at com.example.webenv174jar.XStreamTest.main(XStreamTest.java:27)
Caused by: java.lang.reflect.InaccessibleObjectException: Unable to make field private transient java.util.NavigableMap java.util.TreeSet.m accessible: module java.base does not "opens java.util" to unnamed module @3c9d0b9d
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
    at java.base/java.lang.reflect.Field.checkCanSetAccessible(Field.java:178)
    at java.base/java.lang.reflect.Field.setAccessible(Field.java:172)
    at com.thoughtworks.xstream.core.util.Fields.locate(Fields.java:40)
    at com.thoughtworks.xstream.converters.collections.TreeSetConverter$Reflections.<clinit>(TreeSetConverter.java:135)

I think the problem is at TreeSetConverter -> TreeSetConverter.Reflections.sortedMapField TreeMapConverter -> TreeMapConverter.Reflections.comparatorField Fields.locate -> field.setAccessible(true); related exception also need fix

maybe influence after java9 i guess

[joehni]

This is no bug, this is by design. A TreeSet/TreeMap may have an own Comparator and the Java API has no official way, to get them, therefore reflection is the only way. So, do as the exception says, run your application with run time option "--add-opens java.base/java.util=ALL-UNNAMED"

[urn1ce]

This is no bug, this is by design. A TreeSet/TreeMap may have an own Comparator and the Java API has no official way, to get them, therefore reflection is the only way. So, do as the exception says, run your application with run time option "--add-opens java.base/java.util=ALL-UNNAMED"

I known your meaning, but if i change like this (still not use "--add-opens java.base/java.util=ALL-UNNAMED") public static void main(String[] args) { var ts = new TreeSet

[joehni]

Yes, because how should XStream know, if a comparator has been set? There's just one way: Look into the private field.

[urn1ce]

Yes, because how should XStream know, if a comparator has been set? There's just one way: Look into the private field.

So even if not use comparator, also need "--add-opens java.base/java.util=ALL-UNNAMED", it maybe a bit redundant, if catch and handle exception may have a better experience., but i understand, thank you