Foo.java

    @XmlElementWrapper(name = "Foos", nillable = Config.FOO_NILLABLE)
    @XmlElement(name = "Foo")
    public List<String> foos;

Config.java

public static final Boolean FOO_NILLABLE = true; 
// works
public static final Boolean FOO_NILLABLE = loadConfigValueFromDatabase(); 
// doesn't work - attribute value must be constant

Desired outcome when foos null (or empty)

config = true

<parent>
  <foos xs:nil="true">
</parent>

config = false

<parent>
</parent>

I have Eclipselink 2.7.8 on this project. I’m open to other ways of achieving this outcome but the crux is that once I make the changes this behaviour needs to be configurable rather than depending on further code changes.

UPDATE: The exact implementation of dynamically setting nillable is not essential, but I just need to be able to find a way to selectively switch between <foos> appearing as xs:nil="true" and it not appearing at all