JAXB: How should I marshal complex nested data structures?

Question

I have several complex data structures like

Map< A, Set< B > >
Set< Map< A, B > >
Set< Map< A, Set< B > > >
Map<         


        

Answer 1

I've solved the problem without XmlAdapter's.

I've written JAXB-annotated objects for Map, Map.Entry and Collection.
The main idea is inside the method xmlizeNestedStructure(...):

Take a look at the code:

public final class Adapters {

private Adapters() {
}

public static Class[] getXmlClasses() {
    return new Class[]{
                XMap.class, XEntry.class, XCollection.class, XCount.class
            };
}

public static Object xmlizeNestedStructure(Object input) {
    if (input instanceof Map) {
        return xmlizeNestedMap((Map) input);
    }
    if (input instanceof Collection) {
        return xmlizeNestedCollection((Collection) input);
    }

    return input; // non-special object, return as is
}

public static XMap xmlizeNestedMap(Map input) {
    XMap ret = new XMap();

    for (Map.Entry e : input.entrySet()) {
        ret.add(xmlizeNestedStructure(e.getKey()),
                xmlizeNestedStructure(e.getValue()));
    }

    return ret;
}

public static XCollection xmlizeNestedCollection(Collection input) {
    XCollection