Examples of com.db4o.ObjectContainer.activate()

com.db4o.ObjectContainer.activate()

activates all members on a stored object to the specified depth.

See {@link com.db4o.config.Configuration#activationDepth(int) "Why activation"}for an explanation why activation is necessary.

The activate method activates a graph of persistent objects in memory. Only deactivated objects in the graph will be touched: their fields will be loaded from the database. The activate methods starts from a root object and traverses all member objects to the depth specified by the depth parameter. The depth parameter is the distance in "field hops" (object.field.field) away from the root object. The nodes at 'depth' level away from the root (for a depth of 3: object.member.member) will be instantiated but deactivated, their fields will be null. The activation depth of individual classes can be overruled with the methods {@link com.db4o.config.ObjectClass#maximumActivationDepth maximumActivationDepth()} and{@link com.db4o.config.ObjectClass#minimumActivationDepth minimumActivationDepth()} in the{@link com.db4o.config.ObjectClass ObjectClass interface}.

A successful call to activate triggers Activating and Activated callbacks, which can be used for cascaded activation.

@see com.db4o.config.Configuration#activationDepth Why activation? @see ObjectCallbacks Using callbacks @param obj the object to be activated. @param depth the member {@link com.db4o.config.Configuration#activationDepth depth}to which activate is to cascade. @throws Db4oIOException I/O operation failed or was unexpectedly interrupted. @throws DatabaseClosedException db4o database file was closed or failed to open.

    ObjectContainer oc = Db4o.openFile(configFactory.createConfiguration(), dbFileName);


    List<NewsBin> newsBins = oc.query(NewsBin.class);


    for (INewsBin newsBin : newsBins) {
      oc.activate(newsBin, Integer.MAX_VALUE);
      for (NewsReference newsRef : newsBin.getNewsRefs()) {
        Query query = oc.query();
        query.constrain(News.class);
        query.descend("fId").constrain(newsRef.getId()); //$NON-NLS-1$
        News news = (News) query.execute().iterator().next();

      for (NewsReference newsRef : newsBin.getNewsRefs()) {
        Query query = oc.query();
        query.constrain(News.class);
        query.descend("fId").constrain(newsRef.getId()); //$NON-NLS-1$
        News news = (News) query.execute().iterator().next();
        oc.activate(news, Integer.MAX_VALUE);
        String parentIdFieldName = "fParentId"; //$NON-NLS-1$
        MigrationHelper.setField(news, parentIdFieldName, newsBin.getId().longValue());
        oc.ext().set(news, Integer.MAX_VALUE);
      }
    }


      /* Assert NewsCounter / NewsCounterItem */
      NewsCounter newsCounter = db.query(NewsCounter.class).get(0);
      db.activate(newsCounter, Integer.MAX_VALUE);
      NewsCounter otherNewsCounter = defragmentedDb.query(NewsCounter.class).get(0);
      defragmentedDb.activate(otherNewsCounter, Integer.MAX_VALUE);
      assertNotNull(newsCounter);
      assertNotNull(otherNewsCounter);


      NewsCounterItem item = otherNewsCounter.get("http://www.rssowl.org");
      assertEquals(1, item.getNewCounter());

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