java - appengine - java持久性

Question

我有 3 个相关的类(class):

• 成员(member) 1-n 追踪器
• 链接 1-n 跟踪器

拥有一对多的双向关系

@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.

“增强”是什么意思？

如果我持久化一个没有关系的类，它就可以很好地工作

Answer 1

确保您使用的是 DataNucleus 插件...

这是他们的网站...

link text

...以下是如何将其安装到 Eclipse IDE...

link text

...这里是与 JDO 一起使用它的教程...

link text

希望对您有所帮助，祝您好运。