JAXB: How should I marshal complex nested data structures?

I have several complex data structures like

Map< A, Set< B > >
Set< Map< A, B > >
Set< Map< A, Set< B > > >
Map< A, Map< B, Set< C > > >
and so on (more complex data structures)

Note: In my case it doesn't really matter if I use Set or List.

Now I know that JAXB let me define XmlAdapter's, that's fine, but I don't want to define an XmlAdapter for every of the given data structures (it would be just too much copy-and-paste code).

I tried to achieve my goal by declaring two generalizing XmlAdapters:

• one for Map: MapAdapter<K,V>
• one for Set: SetAdapter<V>

The problem:
JAXB complains as following:

javax.xml.bind.JAXBException:
class java.util.Collections$UnmodifiableMap nor any of its
  super class is known to this context.

Here is my adapter class:

import java.util.*;
import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.*;

public class Adapters {

public final static class MapAdapter<K, V>
        extends XmlAdapter<MapAdapter.Adapter<K, V>, Map<K, V>> {

    @XmlType
    @XmlRootElement
    public final static class Adapter<K, V> {

        @XmlElement
        protected List<MyEntry<K, V>> key = new LinkedList<MyEntry<K, V>>();

        private Adapter() {
        }

        public Adapter(Map<K, V> original) {
            for (Map.Entry<K, V> entry : original.entrySet()) {
                key.add(new MyEntry<K, V>(entry));
            }
        }

    }

    @XmlType
    @XmlRootElement
    public final static class MyEntry<K, V> {

        @XmlElement
        protected K key;

        @XmlElement
        protected V value;

        private MyEntry() {
        }