jpa - 列挙型フィールドを持つ埋め込み可能なクラスを持つエンティティの保存中に ClassCastException を取得する

Question

サーバー: JBoss6 テクノロジー: JPA 2、EJB 3.1

以下に示すように、同じエンティティで何度も使用される、フィールドの共通グループをカプセル化する埋め込み可能なクラスを持つエンティティがあります。

@Entity
@Table(name = "form_x")
public class FormX extends SurveyForm implements Serializable {

    private static final long serialVersionUID = 1321874423212L;

    @Embedded
    @AttributeOverrides({
        @AttributeOverride(name="data", column = @Column(name = "field01")),
        @AttributeOverride(name="metadata", column = @Column(name = "field01_metadata")),
        @AttributeOverride(name="metadataComment", column = @Column(name = "field01_metadata_comment"))
    })
    private SingleSelectionQuestion<Agreement> field1;

    @Embedded
    @AttributeOverrides({
        @AttributeOverride(name="data", column = @Column(name = "field02")),
        @AttributeOverride(name="metadata", column = @Column(name = "field02_metadata")),
        @AttributeOverride(name="metadataComment", column = @Column(name = "field02_metadata_comment"))
    })
    private SingleSelectionQuestion<Frequency> field2;

    ...getters and setters...
}

@Embeddable
public class SingleSelectionQuestion<T> implements Serializable {

    private static final long serialVersionUID = -7389172046941228140L;

    @Enumerated(EnumType.STRING)
    private T data;

    @Enumerated(EnumType.STRING)
    private QuestionMetaData metadata;

    private String metadataComment;

    ...getters and setters...
}

Agreement と Frequency は列挙型です。

しかし、このフォームを保存しようとすると (entityManage#merge で既に永続化されたエンティティに)、次のスタック トレースに見られるように、ClassCastException が発生します。

Caused by: javax.transaction.RollbackException: ARJUNA-16053 Could not commit transaction.
    at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.commitAndDisassociate(TransactionImple.java:1170) [:6.0.0.Final]
    at com.arjuna.ats.internal.jta.transaction.arjunacore.BaseTransaction.commit(BaseTransaction.java:119) [:6.0.0.Final]
    at com.arjuna.ats.jbossatx.BaseTransactionManagerDelegate.commit(BaseTransactionManagerDelegate.java:75) [:6.0.0.Final]
    at org.jboss.ejb3.tx2.impl.CMTTxInterceptor.endTransaction(CMTTxInterceptor.java:82) [:0.0.1]
    ... 110 more
Caused by: javax.persistence.PersistenceException: error during managed flush
    at org.hibernate.ejb.AbstractEntityManagerImpl$3.mapManagedFlushFailure(AbstractEntityManagerImpl.java:1072) [:3.6.0.Final]
    at org.hibernate.transaction.synchronization.CallbackCoordinator.beforeCompletion(CallbackCoordinator.java:122) [:3.6.0.Final]
    at org.hibernate.transaction.synchronization.HibernateSynchronizationImpl.beforeCompletion(HibernateSynchronizationImpl.java:51) [:3.6.0.Final]
    at com.arjuna.ats.internal.jta.resources.arjunacore.SynchronizationImple.beforeCompletion(SynchronizationImple.java:97) [:6.0.0.Final]
    at com.arjuna.ats.arjuna.coordinator.TwoPhaseCoordinator.beforeCompletion(TwoPhaseCoordinator.java:274) [:6.0.0.Final]
    at com.arjuna.ats.arjuna.coordinator.TwoPhaseCoordinator.end(TwoPhaseCoordinator.java:94) [:6.0.0.Final]
    at com.arjuna.ats.arjuna.AtomicAction.commit(AtomicAction.java:159) [:6.0.0.Final]
    at com.arjuna.ats.internal.jta.transaction.arjunacore.TransactionImple.commitAndDisassociate(TransactionImple.java:1158) [:6.0.0.Final]
    ... 113 more
Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Enum
    at org.hibernate.type.EnumType.nullSafeSet(EnumType.java:150) [:3.6.0.Final]
    at org.hibernate.type.CustomType.nullSafeSet(CustomType.java:146) [:3.6.0.Final]
    at org.hibernate.type.ComponentType.nullSafeSet(ComponentType.java:336) [:3.6.0.Final]
    at org.hibernate.persister.entity.AbstractEntityPersister.dehydrate(AbstractEntityPersister.java:2166) [:3.6.0.Final]
    at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:2540) [:3.6.0.Final]
    at org.hibernate.persister.entity.AbstractEntityPersister.updateOrInsert(AbstractEntityPersister.java:2476) [:3.6.0.Final]
    at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:2803) [:3.6.0.Final]
    at org.hibernate.action.EntityUpdateAction.execute(EntityUpdateAction.java:113) [:3.6.0.Final]
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273) [:3.6.0.Final]
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:265) [:3.6.0.Final]
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:185) [:3.6.0.Final]
    at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321) [:3.6.0.Final]
    at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51) [:3.6.0.Final]
    at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216) [:3.6.0.Final]
    at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383) [:3.6.0.Final]
    at org.hibernate.transaction.synchronization.CallbackCoordinator.beforeCompletion(CallbackCoordinator.java:117) [:3.6.0.Final]
    ... 119 more

SingleSelectionQuestion クラスのフィールドで @Enumerated アノテーションを使用しても、このエラーが発生するのはなぜですか?

誰が私が間違っているのか手がかりを持っていますか?

ありがとう。