Matching tags with identical names but different child values

I am trying to use XMLUnit 2 to compare xml files.

<composite>
    <data>
        <subtag>
            <code>1</code>
        </subtag>
        <subtag>
            <code>2</code>
        </subtag>
    </data>
</composite>

Second file is the same, with the only difference being 'subtag' tags switched places.

<composite>
    <data>
        <subtag>
            <code>2</code>
        </subtag>
        <subtag>
            <code>1</code>
        </subtag>
    </data>
</composite>

I've been out of luck so far finding a set of ElementMatchers suitable to match those two as equal.

Is there an out of the box solution for this problem?

This is pretty much identical to the "tr is identified by nested th" example from XMLUnit's user-guide. One solution is to use a conditional ElementSelector and ensure it uses the correct rule when deciding which subtag to take - see https://github.com/xmlunit/user-guide/wiki/SelectingNodes#conditional-elementselectors

In your concrete case something like

ElementSelectors.conditionalBuilder()
    .whenElementIsNamed("subtag")
    .thenUse(ElementSelectors.byXPath("./code", ElementSelectors.byNameAndText))
    .elseUse(ElementSelectors.byName)
    .build();

should do. This assumes your subtags are identified by the nested text of their code child element.