appengine - java持久性

Question

我有 3 个具有关系的类：

• 成员 1-n 跟踪器
• 1-n 跟踪器

链接具有拥有的一对多双向关系的

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Member {
        @PrimaryKey
        @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
        private Key key;

        @Persistent(mappedBy = "member")
        private List<Tracker> trackers;

}

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Link {
        @PrimaryKey
        @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
        private Key key;

        @Persistent(mappedBy = "link")
        private List<Tracker> trackers;

}

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Tracker {
        @PrimaryKey
        @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
        private Key key;

        @Persistent
        private Member member;

        @Persistent
        private Link link;

} 

我创建了一个新的跟踪器：

member = new Member();
member.name = "blah";

link = new Link();
link.url = "http://blahblah.blah";

tracker = new Tracker();
tracker.setMember(member);
tracker.setLink(link);

pm.makePersistent(tracker);//error

它抛出

The class "The class "zodpob.model.Tracker" is not persistable. This
means that it either hasnt been enhanced, or that the enhanced version
of the file is not in the CLASSPATH (or is hidden by an unenhanced
version), or the Meta-Data/annotations for the class are not found."
is not persistable. This means that it either hasnt been enhanced, or
that the enhanced version of the file is not in the CLASSPATH (or is
hidden by an unenhanced version), or the Meta-Data for the class is
not found.

什么是“增强”意味着什么？

如果我坚持一个没有关系的课程，效果很好

Answer 1

确保您使用的是 DataNucleus 插件...

这是他们的网站...

链接文本

。 ..以下是如何将其安装到 Eclipse IDE...

链接文本

...这里是与 JDO 一起使用它的教程...

链接文本

我希望有所帮助，祝你好运。