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我的网络应用突然不允许人们购买我们的产品。我不知道该怎么办。

昨晚我们的一位工程师不小心@Persistent从拥有的一对多字段（在父类中）中删除了标签。他在没有对其进行测试的情况下将其上传到 App Engine 服务器。我们收到报告说人们买不到东西，所以我们查看了更改，进入并恢复了@Persistent标签。

但是现在每次代码尝试修改该字段时都会出现异常。

请帮助-我不知道该怎么做-我们已经添加了@Persistent注释-为什么会发生这种异常？

@PersistenceCapable
public class Published {
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    @PrimaryKey
    private Long id;

    ...
    // see note about this field above
    @Persistent(defaultFetchGroup = "true", mappedBy = "pub")
    private List<License> licenses;
    ...
}


@PersistenceCapable
public class License {
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    @PrimaryKey
    private Key id;
    @Persistent
    private Published pub;
    ...
}

当我创建一个新的 Published 并调用时，会发生以下异常pub.getLicensed().add(new Licensed(...))

Uncaught exception from servlet
java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.String
    at org.datanucleus.store.appengine.DatastoreRelationFieldManager.checkForParentSwitch(DatastoreRelationFieldManager.java:203)
    at org.datanucleus.store.appengine.DatastoreRelationFieldManager$1.setObjectViaMapping(DatastoreRelationFieldManager.java:134)
    at org.datanucleus.store.appengine.DatastoreRelationFieldManager$1.apply(DatastoreRelationFieldManager.java:113)
    at org.datanucleus.store.appengine.DatastoreRelationFieldManager.storeRelations(DatastoreRelationFieldManager.java:82)
    at org.datanucleus.store.appengine.DatastoreFieldManager.storeRelations(DatastoreFieldManager.java:959)
    at org.datanucleus.store.appengine.DatastorePersistenceHandler.storeRelations(DatastorePersistenceHandler.java:585)
    at org.datanucleus.store.appengine.DatastorePersistenceHandler.insertPostProcess(DatastorePersistenceHandler.java:320)
    at org.datanucleus.store.appengine.DatastorePersistenceHandler.insertObjects(DatastorePersistenceHandler.java:272)
    at org.datanucleus.store.appengine.DatastorePersistenceHandler.insertObject(DatastorePersistenceHandler.java:256)
    at org.datanucleus.state.JDOStateManagerImpl.internalMakePersistent(JDOStateManagerImpl.java:3185)
    at org.datanucleus.state.JDOStateManagerImpl.makePersistent(JDOStateManagerImpl.java:3161)
    at org.datanucleus.ObjectManagerImpl.persistObjectInternal(ObjectManagerImpl.java:1298)
    at org.datanucleus.sco.SCOUtils.validateObjectForWriting(SCOUtils.java:1476)
    at org.datanucleus.store.mapped.scostore.ElementContainerStore.validateElementForWriting(ElementContainerStore.java:380)
    at org.datanucleus.store.mapped.scostore.FKListStore.validateElementForWriting(FKListStore.java:609)
    at org.datanucleus.store.mapped.scostore.FKListStore.internalAdd(FKListStore.java:344)
    at org.datanucleus.store.appengine.DatastoreFKListStore.internalAdd(DatastoreFKListStore.java:146)
    at org.datanucleus.store.mapped.scostore.AbstractListStore.add(AbstractListStore.java:105)
    at org.datanucleus.sco.backed.List.add(List.java:649)
    at (my servlet)
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1 回答 1

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看起来 App Engine 错误阻止我上传代码。一旦 GAE 赶上并切换到新代码，一切正常。

作为记录，我不确定是什么修复了它 - 它可能只是添加了@Persistent注释，或者它可能已经更改Published.id为 aKey而不是Long.

于 2013-02-02T21:21:12.250 回答