criteria.list()

@Entity
@Table(name = "source")
public class Source implements Serializable {
   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   @Column(name = "id")
   private long id;
   
   @OneToOne(cascade = CascadeType.ALL)
   @JoinColumn(name = "extraData_fk")
   private ExtraData extraData;
        // skipped other code
}

@Table(name = "extra_data")
public class ExtraData implements Serializable {
   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)
   @Column(name = "id")
   private long id;
   
   @ElementCollection(fetch = FetchType.EAGER)
   @JoinTable(name = "extra_data_properties", joinColumns = @JoinColumn(name = "extra_data_id"))
   @MapKeyColumn(name = "pname")
   @Column(name = "pvalue")
   private Map<String, String> extraProperties;
   // skipped other code
}

public class HibernateTest {
   public static void main(String[] args) {
      SessionFactory sessionFactory = new AnnotationConfiguration().configure("hibernate.cfg.xml").buildSessionFactory();
      
      Session sessionToSave = sessionFactory.openSession();
      
      Transaction txToSave = sessionToSave.beginTransaction();
      txToSave.begin();

      Map<String, String> extraProperties = new HashMap<String, String>(4);
      extraProperties.put("pname1", "pvalue1");
      extraProperties.put("pname2", "pvalue2");
      extraProperties.put("pname3", "pvalue3");
      extraProperties.put("pname4", "pvalue4");
      
      Source source = new Source( new ExtraData("ename", extraProperties) );
      sessionToSave.save(source);
      
      txToSave.commit();

      ///////////////////////////////////////

      Session sessionToFetch = sessionFactory.openSession();
      Transaction txToFetch = sessionToFetch.beginTransaction();
      txToFetch.begin();
      
      Criteria criteria = sessionToSave.createCriteria(Source.class);
      
      System.out.println( criteria.list().size() == 4 );
      
      txToFetch.commit();
   }
}