@XmlJavaTypeAdapter annotation on JAXB class doesn't work for JAX-RS application in EAP 6

Issue

• I have a JAX-RS application and am trying to utilise JAXB-JSON marshaling.
• This is my JAXB class definition:

@XmlRootElement(name = "myData")
public class MyData {
    private Date timestamp;

    public MyData() {}

    @XmlJavaTypeAdapter(value=JaxbDateAdapter.class, type=Date.class)
    @XmlElement(name = "timestamp")
    public Date getTimestamp() { return timestamp; }

    public void setTimestamp(Date timestamp) { this.timestamp = timestamp; }
}

• And this is my JaxbDateAdapter definition:

import javax.xml.bind.annotation.adapters.XmlAdapter;
import java.text.SimpleDateFormat;
import java.text.ParsePosition;
import java.util.Date;

public class JaxbDateAdapter extends XmlAdapter<String, Date> {
    @Override
    public String marshal(Date date) throws Exception {
        return new SimpleDateFormat("yyyy-dd-MM HH:mm:ss z").format(date);
    }

    @Override
    public Date unmarshal(String string) throws Exception {
        return new SimpleDateFormat("yyyy-dd-MM HH:mm:ss z").parse(string, new ParsePosition(0));
    }
}

• However, this XML adapter doesn't seem to work and the date returned is still in millis. Do you have any idea why this may be so?