JAXB注释 – 映射接口和@XmlElementWrapper

@XmlAnyElement
private List<Animal> animals;

一切都正常.但是当我添加一个包装元素时,例如：

@XmlElementWrapper
@XmlAnyElement
private List<Animal> animals;

我发现Java对象正确编组,但是当我解组由编组创建的文档时,我的列表是空的.我已经在代码下面发布了演示此问题的代码.

我做错了什么,或者这是一个错误？我已经尝试使用版本2.1.12和2.2-ea,结果相同.

我正在通过示例来映射带有注释的接口：
https://jaxb.dev.java.net/guide/Mapping_interfaces.html

@XmlRootElement
class Zoo {

  @XmlElementWrapper
  @XmlAnyElement(lax = true)
  private List<Animal> animals;

  public static void main(String[] args) throws Exception {
    Zoo zoo = new Zoo();
    zoo.animals = new ArrayList<Animal>();
    zoo.animals.add(new Dog());
    zoo.animals.add(new Cat());

    JAXBContext jc = JAXBContext.newInstance(Zoo.class,Dog.class,Cat.class);
    Marshaller marshaller = jc.createMarshaller();

    ByteArrayOutputStream os = new ByteArrayOutputStream();
    marshaller.marshal(zoo,os);

    System.out.println(os.toString());

    Unmarshaller unmarshaller = jc.createUnmarshaller();
    Zoo unmarshalledZoo = (Zoo) unmarshaller.unmarshal(new ByteArrayInputStream(os.toByteArray()));

    if (unmarshalledZoo.animals == null) {
      System.out.println("animals was null");
    } else if (unmarshalledZoo.animals.size() == 2) {
      System.out.println("it worked");
    } else {
      System.out.println("failed!");
    }
  }

  public interface Animal {}

  @XmlRootElement
  public static class Dog implements Animal {}

  @XmlRootElement
  public static class Cat implements Animal {}
}