Example 8.1. Persisting Objects
// create some objects Magazine mag = new Magazine ("1B78-YU9L", "JavaWorld"); Company pub = new Company ("Weston House"); pub.setRevenue (1750000D); mag.setPublisher (pub); pub.addMagazine (mag); Article art = new Article ("JDO Rules!", "Transparent Object Persistence"); art.setAuthor (new Person ("Fred", "Hoyle")); mag.addArticle (art); // we only need to make the root object persistent; JDO will traverse // the object graph and make all related objects persistent too PersistenceManager pm = pmFactory.getPersistenceManager (); pm.currentTransaction ().begin (); pm.makePersistent (mag); pm.currentTransaction ().commit (); // or we could continue using the persistence manager... pm.close ();
Example 8.2. Updating Objects
// assume we have an object id for the magazine we want to update Object oid = ...; // read a magazine; note that in order to read objects outside of // transactions you must have the NonTransactionalRead option set PersistenceManager pm = pmFactory.getPersistenceManager (); Magazine mag = (Magazine) pm.getObjectById (oid, false); Company pub = mag.getPublisher (); // updates should always be made within transactions; note that // there is no code explicitly linking the magazine or company // with the transaction; JDO automatically tracks all changes pm.currentTransaction ().begin (); mag.setIssue (23); company.setRevenue (1750000D); pm.currentTransaction ().commit (); // or we could continue using the persistence manager... pm.close ();
Example 8.3. Deleting Objects
// assume we have an object id for the magazine whose articles // we want to delete Object oid = ...; // read a magazine; note that in order to read objects outside of // transactions you must have the NonTransactionalRead option set PersistenceManager pm = pmFactory.getPersistenceManager (); Magazine mag = (Magazine) pm.getObjectById (oid, false); // deletes should always be made within transactions pm.currentTransaction ().begin (); pm.deletePersistentAll (mag.getArticles ()); pm.currentTransaction ().commit (); // or we could continue using the persistence manager... pm.close ();