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 ();