FULL PRODUCT VERSION :
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.14393]

A DESCRIPTION OF THE PROBLEM :
As I was testing with different values of @XmlAttribute(name="?") that a certain xml file requires simply returns a empty result.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
create a default XML compatible class with the settings:
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "")

Add @XmlAttribute(name = "id") to all values.

In main (replace CLASS and CLASS_Object with the class and a object):
JAXBContext context = JAXBContext.newInstance(CLASS.class);
Marshaller m = context.createMarshaller();
m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
m.marshal(CLASS_Object, System.out);

The result of System.out should look like this:
<CLASS id="?" id="?" ... />

Now replace one of the name="id" with one the following:
x
y
lenght

after you run this the result of System.out is empty.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The result of System.out is empty
ACTUAL -
The result of System.out is empty

ERROR MESSAGES/STACK TRACES THAT OCCUR :
There are no errors or messages for this

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "")
@XmlRootElement(name = "node")
public class Node {

    @XmlAttribute(name = "id", required = true)
    protected long id;
    @XmlAttribute(name = "idx", required = true)
    protected long x;
    @XmlAttribute(name = "idy", required = true)
    protected long y;

    public Node() {}

    public Node(long id, long x, long y) {
        this.id = id;
        this.x = x;
        this.y = y;
    }


    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public long getX() {
        return x;
    }

    public void setX(long x) {
        this.x = x;
    }

    public long getY() {
        return y;
    }

    public void setY(long y) {
        this.y = y;
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
changing the name to something that does not fit the required reading values.