Unmarshalling generic list with JAXB

Thanks to Blaise Doughan and his article I've found the solution.

First we need the Wrapper class provided in the article:

@XmlRootElement
public class Wrapper<T> {

  private List<T> items;

  public Wrapper() {
    items = new ArrayList<T>();
  }

  public Wrapper(List<T> items) {
    this.items = items;
  }

  @XmlAnyElement(lax=true)
  public List<T> getItems() {
    return items;
  }
}

Then I've modified the Response class in order to use it:

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Response<T> {

  @XmlElement
  protected String status;

  @XmlElement
  protected Wrapper<T> result;

  ...

  public Response(String status, List<T> result) {
    this.status = status;
    this.result = new Wrapper<>(result);
  }

  ...

  public List<T> getResult() {
    return result.getItems();
  }

  ...
}

Finally the unmarshalling code:

JAXBContext context = JAXBContext.newInstance(Response.class, Project.class, User.class, Wrapper.class);
Unmarshaller unmarshaller = context.createUnmarshaller();

StreamSource source = new StreamSource(new File("responseProject.xml"));
Response<Project> responseProject = (Response<Project>)unmarshaller.unmarshal(source);
System.out.println(responseProject.getStatus());
for (Project project:responseProject.getResult()) System.out.println(project);

source = new StreamSource(new File("responseUser.xml"));
Response<User> responseUser = (Response<User>)unmarshaller.unmarshal(source);
System.out.println(responseUser.getStatus());
for (User user:responseUser.getResult()) System.out.println(user);

I've added the Wrapper class to the context class list.

Alternatively you can add this annotation to the Response class:

@XmlSeeAlso({Project.class, User.class})