JAXB marshall a Collection to a XmlElement and a XmlAttribute in one step

I would like to marshall a Collection as nested attributes.

Right now I have:

@Xm开发者_开发百科lElement(name="entry")
public Collection<Integer> getSizes(){ ... }

which returns:

<entry>1</entry>
<entry>2</entry>

But I would like to get:

<entry id="1"/>
<entry id="2"/>

Is this possible without new classes?

Seems to be impossible without new classes at all. Use XmlAdapter:

class EntryAdapter extends XmlAdapter<EntryAdapter.Entry, Integer>
{
    public EntryAdapter.Entry marshal(Integer id) {
        return new Entry(id);
    }

    public Integer unmarshal(Entry e) {
        return e.getId();
    }

    static class Entry 
    {
        private Integer id;

        public Entry() {}
        public Entry(Integer id) { this.id = id; }

        @XmlAttribute
        public Integer getId() { return id; }
        public void setId(Integer id) { this.id = id; }
    }
}

-

@XmlElement(name="entry")  
@XmlJavaTypeAdapter(EntryAdapter.class)
public Collection<Integer> getSizes(){ ... }

As the accepted answer says, XmlAdapter is the standard JAXB solution.

But if you are using EclipseLink MOXy as your JAXB provider and can use one of its extensions, namely @XmlPath, it can be used to achieve the same result.

To marshal the collection values as attributes, you use it like this:

@XmlPath("entry/@id")
public Collection<Integer> getSizes(){ ... }