@XmlRootElement(name = "ApplicatorUnits")
@XmlAccessorType(XmlAccessType.FIELD)
public class EHDTOApplicatorUnits
{
    @XmlElement(name = "UnitGroup")
    private List<EHDTOUnitGroup> ehdtoUnitGroups;

    public List<EHDTOUnitGroup> getEhdtoUnitGroups()
    {
        return ehdtoUnitGroups;
    }

    public void setEhdtoUnitGroups(List<EHDTOUnitGroup> ehdtoUnitGroups)
    {
        this.ehdtoUnitGroups = ehdtoUnitGroups;
    }
}

@XmlRootElement(name = "UnitGroup")
@XmlAccessorType(XmlAccessType.FIELD)
public class EHDTOUnitGroup
{
    @XmlAttribute(name = "name")
    private String name;

    @XmlElement(name = "unit")
    private List<EHDTOUnit> ehdtoUnits;

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public List<EHDTOUnit> getEhdtoUnits()
    {
        return ehdtoUnits;
    }

    public void setEhdtoUnits(List<EHDTOUnit> ehdtoUnits)
    {
        this.ehdtoUnits = ehdtoUnits;
    }
}

JaxbAnnotationModule jaxbAnnotationModule = new JaxbAnnotationModule();
jaxbAnnotationModule.setPriority(Priority.PRIMARY);
mapper.registerModule(jaxbAnnotationModule);
/*AnnotationIntrospector primary = new JacksonAnnotationIntrospector();
AnnotationIntrospector secondary = new XmlJaxbAnnotationIntrospector(mapper.getTypeFactory()); //new JaxbAnnotationIntrospector(mapper.getTypeFactory());
AnnotationIntrospector pair = new AnnotationIntrospectorPair(primary,secondary);
mapper.setAnnotationIntrospector(pair);*/

<?xml version="1.0"?>
<EHDTOApplicatorUnits>
  <UnitGroup>
    <name>string</name>
    <unit>
      <id>1</id>
      <name>string</name>
      <unitSystem>string</unitSystem>
    </unit>
  </UnitGroup>
</EHDTOApplicatorUnits>

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ApplicatorUnits>
  <UnitGroup name="coefTempErrorSpan">
    <unit>
      <id>1</id>
      <name>% span /10K</name>
      <unitSystem>SI</unitSystem>
    </unit>
    <unit>
      <id>2</id>
      <name>% span /50F</name>
      <unitSystem>SI</unitSystem>
    </unit>
  </UnitGroup>
...
</ApplicatorUnits>