Thanks for the reply, Erick.
I'm trying persist data using JDO (a one-to-many relationship).
I did a code sample that inserted the children, but the parents isn't
linked to those children.
import java.util.ArrayList;
import java.util.List;
import javax.jdo.annotations.Element;
import javax.jdo.annotations.IdGeneratorStrategy;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.IdentityType;
import javax.jdo.annotations.Persistent;
import javax.jdo.annotations.PrimaryKey;
import com.google.appengine.api.datastore.Key;
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = "true")
public class Book {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key id;
private String title;
@Persistent(mappedBy = "book")
@Element(dependent = "true")
private List<Chapter> chapters = new ArrayList<Chapter>();
// getters and setters
}
import javax.jdo.annotations.IdGeneratorStrategy;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.Persistent;
import javax.jdo.annotations.PrimaryKey;
import javax.jdo.annotations.IdentityType;
import com.google.appengine.api.datastore.Key;
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = "true")
public class Chapter {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key id;
private String title;
private int numPages;
@Persistent
private Book book;
// getters and setters
}
Book b = new Book();
b.setTitle("JDO 4eva");
Chapter c1 = new Chapter();
c1.setTitle("Intro");
c1.setNumPages(10);
b.getChapters().add(c1);
Chapter c2 = new Chapter();
c2.setTitle("Configuration");
c2.setNumPages(9);
b.getChapters().add(c2);
pm.currentTransaction().begin();
try {
pm.makePersistent(b);
pm.currentTransaction().commit();
} finally {
if (pm.currentTransaction().isActive()) {
pm.currentTransaction().rollback();
}
}
The book and its chapters are inserted, but when I retrieve that book,
its Chapters List is empty.
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