Java NucleusUserException:无法访问扩展映射超类的实体上的字段

在查询我的google数据存储实例时，我遇到了一个

nucleuserexception

。我正在查询扩展它的类上的

MappedSuperclass

上存在的字段。下面是我的抽象类，其中包含我感兴趣的字段：

@Entity
@MappedSuperclass
@JsonIgnoreProperties({ "password" })
public abstract class AbstractUser implements User {
  @Persistent
  protected String emailAddress;

  public void setEmailAddress(String email) {
     this.emailAddress = email;
  }

  public String getEmailAddress() {
    return this.emailAddress;
  }

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long key;

  //Other stuff.
}

具体实例如下所示：

@Entity
public class Client extends AbstractUser {
//Things that only clients have.
} 

List existingUsersWithEmail = manager
                              .createQuery(
                             "SELECT c from Client AS c WHERE c.emailaddress = :mail")
                             .setParameter("mail", request.getEmailAddress())
                             .getResultList();

失败的查询如下所示：

@Entity
public class Client extends AbstractUser {
//Things that only clients have.
} 

List existingUsersWithEmail = manager
                              .createQuery(
                             "SELECT c from Client AS c WHERE c.emailaddress = :mail")
                             .setParameter("mail", request.getEmailAddress())
                             .getResultList();

例外情况如下：

Cannot access field emailaddress on type org.workouthound.user.Client
org.datanucleus.exceptions.NucleusUserException: Cannot access field emailaddress on type org.workouthound.user.Client
at org.datanucleus.query.compiler.JavaQueryCompiler.getType(JavaQueryCompiler.java:552)
at org.datanucleus.query.compiler.JavaQueryCompiler.getType(JavaQueryCompiler.java:529)
at org.datanucleus.query.symbol.SymbolTable.getType(SymbolTable.java:118)
at org.datanucleus.query.expression.PrimaryExpression.bind(PrimaryExpression.java:118)
at org.datanucleus.query.expression.DyadicExpression.bind(DyadicExpression.java:85)
at org.datanucleus.query.compiler.JavaQueryCompiler.compileFilter(JavaQueryCompiler.java:299)
at org.datanucleus.query.compiler.JPQLCompiler.compile(JPQLCompiler.java:75)
at org.datanucleus.store.query.AbstractJPQLQuery.compileInternal(AbstractJPQLQuery.java:246)
at org.datanucleus.store.query.Query.setImplicitParameter(Query.java:690)
at org.datanucleus.jpa.JPAQuery.setParameter(JPAQuery.java:428)
at org.workouthound.rest.client.UserResources.emailIsRegistered(UserResources.java:55)
at org.workouthound.rest.client.UserResources.createClient(UserResources.java:33)

我是DataNucleus和Google数据存储的新手。我试图按照概述的教程进行学习，但是我很可能错过了一些东西。请让我知道额外的信息是必要的

更新：

---

如果我将字段名更改为

email

以及getter、setter和query，它会工作……为什么？

那里使用的GAE和低级DataNucleus库版本太旧，不受支持。使用GAE JPA插件v2.x作为minimum@DataNucleus谢谢你让我知道。