I posted this right around new years, but I have not seen any responses since then and some of these questions are still eating at me. Can anyone provide any answers to some of the questions that I've asked?
Thanks in advance. "Sean Dockery" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > Hello there. > > I'm fairly new to OJB. I've read several of the tutorials and I'm working > on creating an application from scratch. > > Below are three classes that I wrote. One is my DAO class, the second class > is an inversion-of-control interface that I'm using to populate the object > after locking it in the DAO class, and the last class is a Struts action > which using the DAO class and provides an implementation of the > UserConfigurator interface. > > I was wondering if anyone could provide some feedback and opinions about the > code. I'm mainly curious about the following: > > 1) The exception handling code is omitted from the examples for the sake of > brevity. Is the manner in which I'm handling exceptions correct? > > 2) I've written my retrieval routine to use a persistence broker query. > Using persistence broker queries in this manner is apparently faster. In a > reply in another thread, I read... > > "Philippe Hacquin" <[EMAIL PROTECTED]> wrote in message > news:<[EMAIL PROTECTED]>... > > ... and they are much more efficient, too, because they use the cache. > > This confuses me somewhat. Does this mean that the ODMG personality of OJB > doesn't use caching? Or do OQL queries bypass caching? > > 3) I've chose to perform object deletion using the persistence broker > instead of database.deletePersistent. What is the consequence of using one > over the other? > > 4) The PB transaction mechanism uses database locks. The ODMG personality > uses object locks. Yet, the ODMG personality is less performant than the PB > personality (according to the performance page on the web site.) Last time > I checked, memory operations were less expensive than database I/O--so I > would have expected ODMG to out-perform PB. Can anyone explain this > apparent contradiction? > > 5) I've seen an application that uses OJB that performs updates directly > against the database using JDBC. I suspect that the implication is that > cached objects can become out of sync with data in the database. Does OJB > have a means by which to detect that a row has been changed by another user? > > 6) The auto-retrieve attribute must (apparently) be set to true for ODMG. > This seems a little evil in that I will always be retrieving a graph of > objects instead of the single object in which I'm interested. The > application mentioned in question 5 has severe performance problems related > to database access; I suspect that the root of the performance problems are > being caused by having auto-retrieve set to true for several key entities in > the application. What happens to the behaviour of the ODMG implementation > if auto-retrieve is set to false? (It suggests that this is a no-no on the > web site, but doesn't elaborate on what problems will arise.) Should I be > switching to the PB personality of OJB to avoid problems? > > 7) Why would I choose to use the ODMG personality over the PB personality? > I've seen some (rather unhelpful) replies saying "it depends on your needs" > and I'm looking for something a little more insightful. What does using the > ODMG personality get me? (I'm not sure what "real Object Transactions" are > supposed to be, but that is one of the reasons cited on the web site.) > > Thanks very much for your precious time. It is greatly appreciated. > > UserDao.java: > package catalyst.dao; > import org.apache.ojb.broker.PersistenceBroker; > import org.apache.ojb.broker.query.Criteria; > import org.apache.ojb.broker.query.Query; > import org.apache.ojb.broker.query.QueryFactory; > import org.apache.ojb.odmg.HasBroker; > import org.apache.ojb.odmg.OJB; > import org.odmg.Implementation; > import org.odmg.Transaction; > import catalyst.domain.User; > public class UserDao { > private static UserDao instance = new UserDao(); > private UserDao() { > } > public static UserDao getInstance() { > return instance; > } > private User findUser(Integer userId) throws DaoException { > Implementation odmg = OJB.getInstance(); > Transaction tx = odmg.newTransaction(); > tx.begin(); > try { > PersistenceBroker broker = ((HasBroker) tx).getBroker(); > Criteria criteria = new Criteria(); > criteria.addEqualTo("userId", userId); > Query query = QueryFactory.newQuery(User.class, criteria); > User user = (User) broker.getObjectByQuery(query); > tx.commit(); > return user; > } > catch (Throwable t) { > tx.abort(); > throw new DaoException(t); > } > } > private void storeUser(User user, UserConfigurator configurator) throws > DaoException { > Implementation implementation = OJB.getInstance(); > Transaction tx = implementation.newTransaction(); > tx.begin(); > try { > tx.lock(user, Transaction.WRITE); > configurator.configure(user); > tx.commit(); > } > catch (Throwable t) { > tx.abort(); > throw new DaoException(t); > } > } > public void createUser(UserConfigurator configurator) throws DaoException { > storeUser(new User(), configurator); > } > public void updateUser(Integer userId, UserConfigurator configurator) throws > DaoException { > storeUser(findUser(userId), configurator); > } > public void deleteUser(Integer userId) throws DaoException { > Implementation odmg = OJB.getInstance(); > Transaction tx = odmg.newTransaction(); > tx.begin(); > try { > PersistenceBroker broker = ((HasBroker) tx).getBroker(); > Criteria criteria = new Criteria(); > criteria.addEqualTo("userId", userId); > Query query = QueryFactory.newQuery(User.class, criteria); > broker.deleteByQuery(query); > tx.commit(); > } > catch (Throwable t) { > tx.abort(); > throw new DaoException(t); > } > } > } > > UserConfigurator.java > package catalyst.dao; > import catalyst.domain.User; > public interface UserConfigurator { > public void configure(User user); > } > > UpdateUserAction.java: > package catalyst.actions; > import javax.servlet.http.HttpServletRequest; > import javax.servlet.http.HttpServletResponse; > import org.apache.commons.beanutils.BeanUtils; > import org.apache.struts.action.Action; > import org.apache.struts.action.ActionForm; > import org.apache.struts.action.ActionForward; > import org.apache.struts.action.ActionMapping; > import catalyst.dao.UserConfigurator; > import catalyst.dao.UserDao; > import catalyst.domain.User; > public class UpdateUserAction extends Action { > public ActionForward execute( > ActionMapping mapping, > ActionForm form, > HttpServletRequest request, > HttpServletResponse response) > throws Exception { > final String _username = BeanUtils.getProperty(form, "username"); > final String _password = BeanUtils.getProperty(form, "password"); > final String _firstName = BeanUtils.getProperty(form, "firstName"); > final String _lastName = BeanUtils.getProperty(form, "lastName"); > final String _language = BeanUtils.getProperty(form, "language"); > Integer userId = Integer.valueOf(BeanUtils.getProperty(form, "userId")); > UserDao.getInstance().updateUser(userId, new UserConfigurator() { > public void configure(User user) { > user.setUsername(_username); > user.setPassword(_password); > user.setFirstName(_firstName); > user.setLastName(_lastName); > user.setLanguage(_language); > } > }); > return mapping.findForward("success"); > } > } --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
