Deserialization of heterogeneous list

[cowtowncoder]

Discussed in https://github.com/FasterXML/jackson-dataformat-xml/discussions/786

^{Originally posted by kristofvb November 19, 2025} Hi,

I have some questions about the following sample:

class ParseTest {

    @Test
    void parse() throws Exception {
        var mapper = new XmlMapper();
        var root = mapper.readValue("""
                <root>
                    <foos>
                        <foo sequenceNr="1">somefoo</foo>
                        <foo sequenceNr="2">otherfoo</foo>
                        <bar>something very different</bar>
                    </foos>
                </root>
                """, Root.class);
        System.out.println(root);
    }

    private static class Root {
        @JacksonXmlProperty(localName = "foos")
        private List<Foo> foos = new ArrayList<>();

        public String toString() {
            return "Root{" +
                    "foos=" + foos +
                    '}';
        }
    }

    private static class Foo {
        @JacksonXmlText
        String text;

        @JacksonXmlProperty(isAttribute = true)
        Integer sequenceNr;

        public String toString() {
            return "Foo{" +
                    "text='" + text + '\'' +
                    ", sequenceNr=" + sequenceNr +
                    '}';
        }
    }

}

• is there a way to make sure the foos list only contains Foo instances for actual foo elements and avoid turning the bar element into a Foo instance?
• is there a way (annotation) to sort the foos list on sequenceNr of the elements? Currently I sort the list in the foos setter (which I omitted in the sample).

Thanks for looking into this.

[cowtowncoder]

(by @kristofvb)

---

This test fails

class ParseTest {

    @Test
    void parse() throws Exception {
        var mapper = new XmlMapper();
        var root = mapper.readValue("""
                <root>
                    <foos>
                        <foo sequenceNr="1">somefoo</foo>
                        <foo sequenceNr="2">otherfoo</foo>
                        <bar>something very different</bar>
                    </foos>
                </root>
                """, Root.class);
        assertEquals(List.of(new Foo("somefoo", 1), new Foo("otherfoo", 2)), root.foos);
    }

    static class Root {
        @JacksonXmlProperty
        List<Foo> foos = new ArrayList<>();
    }

    static class Foo {
        @JacksonXmlText
        String text;
        @JacksonXmlProperty(isAttribute = true)
        Integer sequenceNr;

        public Foo() {
        }

        public Foo(String text, Integer sequenceNr) {
            this.text = text;
            this.sequenceNr = sequenceNr;
        }

        @Override
        public String toString() {
            return "Foo{" +
                    "text='" + text + '\'' +
                    ", sequenceNr=" + sequenceNr +
                    '}';
        }
    }

}