jaxb XmlAccessType: PROPERTY example

I'm trying to use jaxb an开发者_如何学Pythond want to use the 'XmlAccessType.PROPERTY' to let jaxb use getters/setters rather than variable directly, but get different errors depending on what I try, or the variable isn't set at all like I want.

Any good link or pointer to a simple example?

For example, the below makes the groupDefintion not to be set when parsing the xml document:

@XmlAccessorType(javax.xml.bind.annotation.XmlAccessType.PROPERTY)
public class E {
    private EGroup groupDefinition;

    public EGroup getGroupDefinition () {
        return groupDefinition;
    }
    @XmlAttribute
    public void setGroupDefinition (EGroup g) {
        groupDefinition = g;
    }
}

The answer is that your example is not wrong per se, but there are a few possible pitfalls. You have put the annotation on the setter, not the getter. While the JavaDoc for @XmlAttribute does not state any restrictions on this, other annotations (e.g. @XmlID) specifically allow annotation either the setter or the getter, but not both.

Note that @XmlAttribute expects an attribute, not an element. Also, since it parses an attribute, it can't be a complex type. So EGroup could be an enum, perhaps?

I expanded your example and added some asserts, and it works "on my machine", using the latest Java 6.

@XmlRootElement
@XmlAccessorType(javax.xml.bind.annotation.XmlAccessType.PROPERTY)
public class E {

    private EGroup groupDefinition;

    public EGroup getGroupDefinition () {
        return groupDefinition;
    }
    @XmlAttribute
    public void setGroupDefinition (EGroup g) {
        groupDefinition = g;
    }

    public enum EGroup {
        SOME,
        OTHERS,
        THE_REST
    }

    public static void main(String[] args) throws JAXBException {
        JAXBContext jc = JAXBContext.newInstance(E.class);

        E eOne = new E();
        eOne.setGroupDefinition(EGroup.SOME);

        Marshaller m = jc.createMarshaller();
        m.setProperty(Marshaller.JAXB_FRAGMENT, Boolean.TRUE);
        StringWriter writer = new StringWriter();
        m.marshal(eOne, writer);

        assert writer.toString().equals("<e groupDefinition=\"SOME\"/>");

        E eTwo = (E) jc.createUnmarshaller().unmarshal(new StringReader(writer.toString()));

        assert eOne.getGroupDefinition() == eTwo.getGroupDefinition();
    }
}