[appengine-java] JDO Mapping issue : A parent cannot be established or changed once an object has been persisted.

[niraj]

I have three classes

Album{
  Artist albumArtist;
    @Persistent(mappedBy = "parent")
    @Element(dependent = "true")
   List<Song> songs;
}

Song{
  Artist singer;
  Album parent;
}

Artist{
  String name;
}


If I use the Artist instance I create for Album for Song(singer) - I
get an error

javax.jdo.JDOFatalUserException: Detected attempt to establish Album
(1) as the parent of Album(1)/Song(2)/Artist(3) but the entity
identified by Album(1)/Song(2)/Artist(3) is already a child of Album
(1)/Song(2).  A parent cannot be established or changed once an object
has been persisted.

CODE -  THIS throws the above error

        Artist artist = new Artist("First", "LastN", "First Last");
        Album album = new Album("Ahat and album", artist, 1978);
        Song song = new Song("Som song", album, artist);
        album.addSong(song);
        dao.makePersistantAndCommit(album);


CODE: This works

        Artist artist = new Artist("First", "LastN", "First Last");
        Artist artist2 = new Artist("Second", "LastN", "Second Last");
        Album album = new Album("Ahat and album", artist, 1978);
        Song song = new Song("Som song", album, artist2);
        album.addSong(song);
        dao.makePersistantAndCommit(album);

>From my app requirements standpoint - I can have an Artist who is the
albumArtist and who is also the singer. And hence I have a need to use
the Artist instance.

Inputs

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