import java.util.SortedMap; import java.util.TreeMap; import javax.persistence.Entity; //---------------- @Entity class Person { public SortedMap<String, String> memberships = new TreeMap<String, String>(); } //Person
import javax.jdo.PersistenceManager; import javax.persistence.Entity; import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.LockModeType; import javax.persistence.Persistence; //---------------- @Entity public class Test { //---------------- public static void main(String[] args) { EntityManagerFactory emf = Persistence.createEntityManagerFactory( "objectdb:D:\\eclipse\\workspace\\TestProject\\Storage.odb"); EntityManager em = emf.createEntityManager(); Person p = new Person(); p.memberships.put("Bar Association", "President"); em.getTransaction().begin(); em.persist(p); em.getTransaction().commit(); System.out.println("Created memberships: " + p.memberships); emf.close(); //------- emf = Persistence.createEntityManagerFactory( "objectdb:D:\\eclipse\\workspace\\TestProject\\Storage.odb"); em = emf.createEntityManager(); p = em.find(Person.class, 1); System.out.println("Retrieved memberships: " + p.memberships); emf.close(); } //main //---------------- } //Test
Produces console output:
Created memberships: {Bar Association=President} Retrieved memberships: {}