2
我试图加载用户的全部的对象图,它包含一个 收集甲板,然后包含的卡的集合,作为 例如: 用户:问题拆卸整个对象图中GAE-J与JDO
@PersistenceCapable(detachable = "true")
@Inheritance(strategy = InheritanceStrategy.SUBCLASS_TABLE)
@FetchGroup(name = "decks", members = { @Persistent(name =
"_Decks") })
public abstract class User {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
protected Key _ID;
@Persistent
protected String _UniqueIdentifier;
@Persistent(mappedBy = "_Owner")
@Element(dependent = "true")
protected Set<Deck> _Decks;
protected User()
{
}
}
每个甲板上有卡的集合,因为这样的:
@PersistenceCapable(detachable = "true")
@FetchGroup(name = "cards", members = { @Persistent(name =
"_Cards") })
public class Deck {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key _ID;
@Persistent
String _Name;
@Persistent(mappedBy = "_Parent")
@Element(dependent = "true")
private Set<Card> _Cards = new HashSet<Card>();
@Persistent
private Set<String> _Tags = new HashSet<String>();
@Persistent
private User _Owner;
}
最后,每张卡:
@PersistenceCapable
public class Card {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key _ID;
@Persistent
private Text _Question;
@Persistent
private Text _Answer;
@Persistent
private Deck _Parent;
}
我想检索,然后分离整个对象图。我在 可以看到在调试器,它加载好,但然后当我到达 分离,我不能做任何超出用户对象加载。 (没有 甲板,没有卡)。起初,我试图没有交易,只是 “分离”前触摸附加对象上的所有字段,但 没有帮助。然后,我尝试将所有内容添加到默认提取 组,但刚刚生成了关于GAE不支持 联合的警告。我试着将抓取计划的最大抓取深度设置为-1,但是 没有这样做。最后,我尝试使用FetchGroups,你可以在上面看到 ,然后用下面的代码检索:
PersistenceManager pm = _pmf.getPersistenceManager();
pm.setDetachAllOnCommit(true);
pm.getFetchPlan().setGroup("decks");
pm.getFetchPlan().setGroup("cards");
Transaction tx = pm.currentTransaction();
Query query = null;
try {
tx.begin();
query = pm.newQuery(GoogleAccountsUser.class); //Subclass of User
query.setFilter("_UniqueIdentifier == TheUser");
query.declareParameters("String TheUser");
List<User> results = (List<User>)query.execute(ID); //ID = Supplied
parameter
//TODO: Test for more than one result and throw
if(results.size() == 0)
{
tx.commit();
return null;
}
else
{
User usr = (User)results.get(0);
//usr = pm.detachCopy(usr);
tx.commit();
return usr;
}
} finally {
query.closeAll();
if (tx.isActive())
{
tx.rollback();
}
pm.close();
}
这也不起作用,而我运行的想法......
将setGroup()更改为addGroup()完全修复了它。谢谢!令人惊讶的是,我几乎所有的东西都可以正确使用,而且一个小小的错误使我耗费数日时间......我猜想它会发生什么,以致于不熟悉复杂框架。 – tempy 2010-03-09 15:12:39