SUGGESTED FIX

Add the following class to the file java/beans/MetaData.java:

class java_util_Collections {

    static final class EmptyList_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            return new Expression(oldInstance, Collections.class, "emptyList", null);
        }
    }

    static final class EmptySet_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            return new Expression(oldInstance, Collections.class, "emptySet", null);
        }
    }

    static final class EmptyMap_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            return new Expression(oldInstance, Collections.class, "emptyMap", null);
        }
    }

    static final class SingletonList_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = (List) oldInstance;
            return new Expression(oldInstance, Collections.class, "singletonList", new Object[]{list.get(0)});
        }
    }

    static final class SingletonSet_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Set set = (Set) oldInstance;
            return new Expression(oldInstance, Collections.class, "singletonSet", new Object[]{set.iterator().next()});
        }
    }

    static final class SingletonMap_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Map map = (Map) oldInstance;
            Object key = map.keySet().iterator().next();
            return new Expression(oldInstance, Collections.class, "singletonMap", new Object[]{key, map.get(key)});
        }
    }

    static final class UnmodifiableCollection_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new ArrayList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "unmodifiableCollection", new Object[]{list});
        }
    }

    static final class UnmodifiableList_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new LinkedList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "unmodifiableList", new Object[]{list});
        }
    }

    static final class UnmodifiableRandomAccessList_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new ArrayList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "unmodifiableList", new Object[]{list});
        }
    }

    static final class UnmodifiableSet_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Set set = new HashSet((Set) oldInstance);
            return new Expression(oldInstance, Collections.class, "unmodifiableSet", new Object[]{set});
        }
    }

    static final class UnmodifiableSortedSet_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            SortedSet set = new TreeSet((SortedSet) oldInstance);
            return new Expression(oldInstance, Collections.class, "unmodifiableSortedSet", new Object[]{set});
        }
    }

    static final class UnmodifiableMap_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Map map = new HashMap((Map) oldInstance);
            return new Expression(oldInstance, Collections.class, "unmodifiableMap", new Object[]{map});
        }
    }

    static final class UnmodifiableSortedMap_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            SortedMap map = new TreeMap((SortedMap) oldInstance);
            return new Expression(oldInstance, Collections.class, "unmodifiableSortedMap", new Object[]{map});
        }
    }

    static final class SynchronizedCollection_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new ArrayList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "synchronizedCollection", new Object[]{list});
        }
    }

    static final class SynchronizedList_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new LinkedList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "synchronizedList", new Object[]{list});
        }
    }

    static final class SynchronizedRandomAccessList_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new ArrayList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "synchronizedList", new Object[]{list});
        }
    }

    static final class SynchronizedSet_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Set set = new HashSet((Set) oldInstance);
            return new Expression(oldInstance, Collections.class, "synchronizedSet", new Object[]{set});
        }
    }

    static final class SynchronizedSortedSet_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            SortedSet set = new TreeSet((SortedSet) oldInstance);
            return new Expression(oldInstance, Collections.class, "synchronizedSortedSet", new Object[]{set});
        }
    }

    static final class SynchronizedMap_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Map map = new HashMap((Map) oldInstance);
            return new Expression(oldInstance, Collections.class, "synchronizedMap", new Object[]{map});
        }
    }

    static final class SynchronizedSortedMap_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            SortedMap map = new TreeMap((SortedMap) oldInstance);
            return new Expression(oldInstance, Collections.class, "synchronizedSortedMap", new Object[]{map});
        }
    }

    static final class CheckedCollection_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new ArrayList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "checkedCollection", new Object[]{list});
        }
    }

    static final class CheckedList_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new LinkedList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "checkedList", new Object[]{list});
        }
    }

    static final class CheckedRandomAccessList_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            List list = new ArrayList((Collection) oldInstance);
            return new Expression(oldInstance, Collections.class, "checkedList", new Object[]{list});
        }
    }

    static final class CheckedSet_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Set set = new HashSet((Set) oldInstance);
            return new Expression(oldInstance, Collections.class, "checkedSet", new Object[]{set});
        }
    }

    static final class CheckedSortedSet_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            SortedSet set = new TreeSet((SortedSet) oldInstance);
            return new Expression(oldInstance, Collections.class, "checkedSortedSet", new Object[]{set});
        }
    }

    static final class CheckedMap_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            Map map = new HashMap((Map) oldInstance);
            return new Expression(oldInstance, Collections.class, "checkedMap", new Object[]{map});
        }
    }

    static final class CheckedSortedMap_PersistenceDelegate extends PersistenceDelegate {
        protected Expression instantiate(Object oldInstance, Encoder out) {
            SortedMap map = new TreeMap((SortedMap) oldInstance);
            return new Expression(oldInstance, Collections.class, "checkedSortedMap", new Object[]{map});
        }
    }
}
                                     

EVALUATION

1. I can change the spelling from "id" to "ID" (XML encoding of the Java DTrace API on Solaris 10 update 4 will not work with Java 6 until that change is integrated).

2. To avoid breaking immutable classes, XML encoding should work for at least the following:
- Collections.unmodifiableList()
- Collections.unmodifiableSet()
- Collections.unmodifiableMap()
But shouldn't there be a custom persistence delegate for every class returned by any of the java.util.Collections methods?
                                     

EVALUATION

Unfortunately XMLEncoder does not support non-public classes,
so I should create separate persistence delegate for all classes in Collections.
                                     

EVALUATION

This is regression after the fix of the bug 4741757.
Old version of DefaultPersistenceDelegate uses private fields instead properties.
We should not rollback the fix by security reason, but we should solve 2 problems here:

 1. Illegal property name
"public int getID()" means that property name is "ID" (not "id").
So user should follow the JavaBeans specification (section 8.8).
We can try to create a hack but it is a bad idea.

 2. Persistence for private classes like Collections.UnmodifiableList
We can create custom persistence delegates for classes in Collections,
but we can't create common solution for all such classes.
The field access (that was removed by the fix of the bug 4741757) can't fix this problem,
because it is possible to create user's bean with unmodifiable list.