java - JDO 枚举实现接口(interface)

Question

我正在尝试创建一个 JDO 持久化类，它包含一个实现特定接口(interface)的枚举列表。这是代码:

public interface Column {

}

public enum ColumnType1 implements Column {
    VALUE11, VALUE12
}

public enum ColumnType2 implements Column {
    VALUE21, VALUE22
}

这是持久类:

@PersistenceCapable(detachable = "true")
public class ListTable implements Serializable {

    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.UUIDHEX)
    @Column(jdbcType = "VARCHAR", length = 32)
    private String encodedKey;

    // the list of columns that can be displayed in the table
    @Persistent(defaultFetchGroup = "true", nullValue = NullValue.EXCEPTION)
    private List<Column> columns;

    // constructor and getters ...
}

问题是我遇到了这个错误:

javax.jdo.JDOUserException: The MetaData for the element class "com.example.shared.model.Column" of the collection field "com.example.shared.model.ListTable.columns" was not found.
at org.datanucleus.jdo.NucleusJDOHelper.getJDOExceptionForNucleusException(NucleusJDOHelper.java:497)
at org.datanucleus.jdo.JDOPersistenceManager.jdoMakePersistent(JDOPersistenceManager.java:671)
at org.datanucleus.jdo.JDOPersistenceManager.makePersistent(JDOPersistenceManager.java:691)

当我尝试保留 ListTable 时。您对我可以做些什么来保留实现特定接口(interface)的枚举列表有什么建议吗？

Answer 1

接口(interface)的“二级对象”(SCO) 实现不是 JDO 持久类型(请参阅 JDO 规范)。接口(interface)用于持久类型 (FCO)