Jackson xml mapper wraps generic list elements into a listname extra tag

Question

I'm stuck on a wrong XML serialization I'm obtaining with Jackson XML mapper serializer. I have a generic RESULT TAG that must contain some other elements, and these elements may be lists of elements, something like this:

<RESULT>
    <THINGS>
        <THING>
            <SOMETHING_ABOUT_THING>001</SOMETHING_ABOUT_THING>
        </THING>
        <THING>
            <SOMETHING_ABOUT_THING>002</SOMETHING_ABOUT_THING>
        </THING>
    </THINGS>
</RESULT>

But what I'm obtaining through standard XML mapper is something with an extra tag like this:

<RESULT>
    <THINGS>
        <THING>
            <SOMETHING_ABOUT_THING>001</SOMETHING_ABOUT_THING>
        </THING>
    </THINGS>
    <THINGS>
        <THING>
            <SOMETHING_ABOUT_THING>002</SOMETHING_ABOUT_THING>
        </THING>
    </THINGS>
</RESULT>

I do not have any custom object, because tag names and tag content are dynamically retrieved from a database, I'm just working with an HashMap, and trying to serialize it. The hashmap holds a single THINGS key that contains as value a list of maps, and each map contains a single THING element.

What can I do to achieve the first result?

Thanks in advance