No @XmlRootElement annotation

If you get "Expected elements are (none)" in a javax.xml.bind.UnmarshalException, you probably don't have an @XmlRootElement annotation in the Java object that your code is unmarshalling to.

For example, this error:

javax.xml.bind.UnmarshalException: unexpected element (uri:"", local:"customer"). Expected elements are (none)

when unmarshalling this XML:

<?xml version="1.0" encoding="UTF-8"?>
<customer id="100">
    <age>23</age>
    <name>Daffy Duck</name>
</customer>

to this class, is fixed by adding the annotation @XmlRootElement to the class so it looks like this:

import javax.xml.bind.annotation.*;

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "customerType", propOrder = {
        "id",
        "name",
        "age"
})
public class Customer {

    @XmlElement
    String name;
    @XmlElement
    int age;
    @XmlAttribute
    int id;

}