使用jaxb2Marshaller用于Datanucleus Entity

Question

我正在使用Spring 3 MVC框架和Google App Engine Datanucleus JPA构建应用程序， 我的实体类看起来像这样：

@Entity
@XmlRootElement
public class Incident {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Extension(vendorName = "datanucleus", key = "gae.encoded-pk", value = "true")
  private String incidentId;

  @Persistent
  @Extension(vendorName = "datanucleus", key = "gae.pk-id", value = "true")
  private Long keyId;

  private List<String> requests;

  @XmlElement(name="sr")
  public List<String> getRequests() {
    return requests;
  }

  public void setRequests(List<String> requests) {
    this.requests = requests;
  }

  [...]
}    

我正在尝试使用jaxb2Marshalleg r -将其发送到其他应用程序但是当我有@XmlElement(name="sr")注释时，我得到了：

2012-08-07 10:02:17 org.datanucleus.metadata.AbstractClassMetaData determineObjectIdClass 
SEVERE: Class pl.km.smartcity.datastore.Incident has application-identity and no objectid-class specified yet has 0 primary key fields. 
Unable to use SingleFieldIdentity.
Class pl.km.smartcity.datastore.Incident has application-identity and no objectid-class specified yet has 0 primary key fields. Unable to use SingleFieldIdentity.

当我删除这个注释时，它可以工作，但当我传递对象时，我的请求列表当然没有传递。