Xml type resolver fails with NPE when property name is not specified in polymorphic (de)serialization

[MichalStehlikCz]

If property name is not specified in polymorphic serialization, serialization fails as in following example

public class XmlPolyTest {

  @JsonTypeInfo(use = DEDUCTION)
  @JsonSubTypes(@JsonSubTypes.Type(Child1.class))
  public interface Parent {}

  public static class Child1 implements Parent {
    private final String property1;

    @JsonCreator(mode = Mode.PROPERTIES)
    public Child1(String property1) {
      this.property1 = property1;
    }

    public String getProperty1() {
      return property1;
    }
  }

  @Test
  void jacksonXmlTest() throws JsonProcessingException {
    var xmlMapper = new XmlMapper();
    assertThat(xmlMapper.writeValueAsString(new Child1("value1")))
        .contains("<property1>value1</property1>");
  }
}

Produces

java.lang.NullPointerException
	at com.fasterxml.jackson.dataformat.xml.util.StaxUtil.sanitizeXmlTypeName(StaxUtil.java:81)
	at com.fasterxml.jackson.dataformat.xml.XmlTypeResolverBuilder.typeProperty(XmlTypeResolverBuilder.java:45)
	at com.fasterxml.jackson.dataformat.xml.XmlTypeResolverBuilder.typeProperty(XmlTypeResolverBuilder.java:25)
	at com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector._findTypeResolver(JacksonAnnotationIntrospector.java:1517)

Workaround is to specify dummy property name (which is ignored in use=DEDUCTION), but there should be probably nullness check (probably in XmlTypeResolverBuilder#typeProperty around call to StaxUtil.sanitizeXmlTypeName?)

[cowtowncoder]

Thank you for reporting this.

Agreed, NPE should not be exposed. I assume this is with 2.12.1?