@XmlRootElement(name = "rss")
public class Rss {

    public Rss.Channel getChannel() {
        return channel;
    }

// some getters and setters ....

    @XmlAccessorType(XmlAccessType.FIELD)
    @XmlType(name = "", propOrder = {
        "title",
        "link",
        "description",
        "image",
        "lastBuildDate",
        "item"
    })
    public static class Channel {

        @XmlElement(required = true)
        protected String title;
// another properties ....       
        protected List<Rss.Channel.Item> item;

        public String getTitle() {
            return title;
        }

// another getters and setters ....

        public List<Rss.Channel.Item> getItem() {
            if (item == null) {
                item = new ArrayList<Rss.Channel.Item>();
            }
            return this.item;
        }
// and so on....
}
}

JAXBContext jc = JAXBContext.newInstance("com.ar.ya");
Unmarshaller unmarshaller = jc.createUnmarshaller();
File customerXML = new File("src/ya.xml"); //в перспективе это будет стрим с URL
Rss rss = (Rss) JAXBIntrospector.getValue(unmarshaller.unmarshal(customerXML));

Rss rss = (Rss) JAXBIntrospector.getValue(unmarshaller.unmarshal(customerXML));