http://stackoverflow.com/questions/2679759/update-query-in-google-app-engine-data-store-java
package gaej.example.contact.server;
import gaej.example.contact.client.Contact;
import java.util.List;
import javax.jdo.JDOHelper; import javax.jdo.PersistenceManager; import javax.jdo.PersistenceManagerFactory;
public class ContactJdoDAO implements ContactDAO {
private static final PersistenceManagerFactory pmfInstance = JDOHelper
.getPersistenceManagerFactory("transactions-optional");
public static PersistenceManagerFactory getPersistenceManagerFactory() {
return pmfInstance;
}
public void addContact(Contact contact) {
PersistenceManager pm = getPersistenceManagerFactory()
.getPersistenceManager();
try {
pm.makePersistent(contact);
} finally {
pm.close();
}
}
@SuppressWarnings("unchecked")
public List<Contact> listContacts() {
PersistenceManager pm = getPersistenceManagerFactory()
.getPersistenceManager();
String query = "select from " + Contact.class.getName();
return (List<Contact>) pm.newQuery(query).execute();
}
public void removeContact(Contact contact) {
PersistenceManager pm = getPersistenceManagerFactory()
.getPersistenceManager();
try {
pm.currentTransaction().begin();
// We don't have a reference to the selected Product.
// So we have to look it up first,
contact = pm.getObjectById(Contact.class, contact.getId());
pm.deletePersistent(contact);
pm.currentTransaction().commit();
} catch (Exception ex) {
pm.currentTransaction().rollback();
throw new RuntimeException(ex);
} finally {
pm.close();
}
}
public void updateContact(Contact contact) {
PersistenceManager pm = getPersistenceManagerFactory()
.getPersistenceManager();
String name = contact.getName();
String phone = contact.getPhone();
String email = contact.getEmail();
try {
pm.currentTransaction().begin();
// We don't have a reference to the selected Product.
// So we have to look it up first,
contact = pm.getObjectById(Contact.class, contact.getId());
contact.setName(name);
contact.setPhone(phone);
contact.setEmail(email);
pm.makePersistent(contact);
pm.currentTransaction().commit();
} catch (Exception ex) {
pm.currentTransaction().rollback();
throw new RuntimeException(ex);
} finally {
pm.close();
}
}
}
