Examples of com.sun.sgs.app.DataManager

com.sun.sgs.app.DataManager
Provides facilities for managing access to shared, persistent objects. Managed objects are objects that implement the {@link ManagedObject} and{@link Serializable} interfaces. Each managed object is stored separatelyalong with all of the serializable, non-managed objects it refers to. If a managed object refers to another managed object, it must do so through an instance of {@link ManagedReference}, created by the {@link #createReference createReference} method. Attempting to store a reference to a managedobject using a standard reference rather than an instance of ManagedReference will typically result in an {@link ObjectIOException} being thrown when the current transaction commits.
Managed objects that are bound to names, and any managed objects they refer to directly or indirectly, are stored by the DataManager. It is up to the application to determine when managed objects are no longer needed and to remove them explicitly from the DataManager using the {@link #removeObject removeObject} method.
Managed objects are in one of the following states with respect to the data manager:
- Transient - A managed object that has been created directly by the application and has not been supplied in a call to {@link #setBinding setBinding}, {@code createReference}, or {@link #getObjectId getObjectId}. Transient objects are not known to the data manager and are not stored persistently.
  Passing a transient object to {@code setBinding}, {@code createReference}, or {@code getObjectId} creates a new entry for theobject in the data manager. Calling {@code removeObject} or {@link #markForUpdate markForUpdate} on a transient object does not change thestate of the object. If a transient object implements {@link ManagedObjectRemoval}, though, then calling {@code removeObject} willcause its {@link ManagedObjectRemoval#removingObject removingObject}method to be called.
- Persistent - A managed object that has been stored in the data manager by calling {@code setBinding}, {@code createReference}, or {@code getObjectId} in the current transaction, orelse retrieved from the data manager by calling {@link #getBinding getBinding}, {@link #getBindingForUpdate getBindingForUpdate}, {@link ManagedReference#get ManagedReference.get}, or {@link ManagedReference#getForUpdate ManagedReference.getForUpdate}.
  Passing a persistent object to {@code setBinding}, {@code createReference}, {@code markForUpdate}, or {@code getObjectId} does notcreate a new entry for that object in the data manager, but rather reuses the existing one. Calling {@code removeObject} on a persistentobject removes it from the data manager, meaning it will no longer be stored persistently, and changes its state to removed. Note that a managed object made persistent in the current transaction is automatically marked for update, so there is no need to call {@code markForUpdate} for such objects, in particular in theirconstructors.
- Removed - A managed object that has been removed from the data manager by calling {@code removeObject}. Removed objects are no longer stored persistently, although the data manager makes an effort to track which managed objects have been removed.
  Only persistent managed objects can become removed; calling {@code removeObject} on a transient managed object leaves it as a transientobject. Passing a removed managed object to {@code setBinding}, {@code removeObject}, {@code markForUpdate}, {@code createReference}, or {@code getObjectId}, as well as calling {@code ManagedReference.get} or {@code ManagedReference.getForUpdate} on a reference to the removed object,will cause a {@link ObjectNotFoundException} to be thrown, if the systemhas tracked the object's removed state.
- Stale - A managed object that was persistent or removed in another, completed transaction. Stale objects are objects that have become detached from the data manager, and should not be visible to applications that avoid using static fields, but may be encountered under some circumstances. The data manager implementation may or may not track stale objects. If stale objects are not tracked, they will be considered transient.
  Passing a stale object to {@code setBinding}, {@code removeObject}, {@code markForUpdate}, {@code createReference}, or {@code getObjectId}, as well as calling {@code ManagedReference.get} or {@code ManagedReference.getForUpdate} on a reference to the stale object, willcause a {@link TransactionNotActiveException} to be thrown, if thesystem has tracked the object's stale state.
Because storing a managed object in a name binding or creating a managed reference to it causes the object to be stored in data manager, applications should insure that they remove such objects if they end up not referring to them persistently. The {@code removeObject} method does not throwexceptions when called on a transient object, so applications should call {@code removeObject} whenever there is an object that may have becomepersistent and they are sure is no longer used.
Some implementations may need to be notified when managed objects and the objects they refer to are modified, while other implementations may be configurable to detect these modifications automatically. Applications are always permitted to mark objects that have been modified, and doing so may produce performance improvements regardless of whether modifications are detected automatically. @see AppContext#getDataManager @see ManagedObject @see ManagedReference @see Serializable

    /** {@inheritDoc} */
    @Override
    public E poll() {
  E element = null;
  if (headRef != null) {
      DataManager dataManager = AppContext.getDataManager();
      dataManager.markForUpdate(this);
      Entry<E> head = getHeadForUpdate();
      element = head.getElement();
      headRef = head.nextEntryRef;
      if (headRef == null) {
    // last element removed
    tailRef = null;
      }
      dataManager.removeObject(head);
      dataManager.removeObject(element);
  }
  return element;
    }

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    /* -- Implement Object.hashCode -- */


    /** {@inheritDoc} */
    @Override
    public int hashCode() {
  DataManager dataManager = AppContext.getDataManager();
  return dataManager.createReference(this).getId().hashCode();
    }

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    public boolean equals(Object o) {
        if (o == null || !(o instanceof ManagedQueue)) {
            return false;
        }
        ManagedQueue<E> d = Objects.uncheckedCast(o);
        DataManager dm = AppContext.getDataManager();
        return dm.createReference(this).getId().equals(
                dm.createReference(d).getId());
    }

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        } catch (MissingResourceException mre) {
            cm = null;
        }
        channelManager = cm;


        DataManager dm;
        try {
            dm = managerComponents.getComponent(DataManager.class);
        } catch (MissingResourceException mre) {
            dm = null;
        }

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     * regarding the structure's performance.
     */
    public ScalableDeque() {
        backingMap = new ScalableHashMap<Element<E>, Long>();


        DataManager dm = AppContext.getDataManager();
        backingMapRef = dm.createReference(backingMap);


        // initialize the pointers to the front and end of the deque
        // to null.  However, the reference to these pointers will
        // always be non-null
        ManagedSerializable<ManagedReference<Element<E>>> head =
                new ManagedSerializable<ManagedReference<Element<E>>>(null);
        ManagedSerializable<Long> headCount =
                new ManagedSerializable<Long>(-1L);


        ManagedSerializable<ManagedReference<Element<E>>> tail =
                new ManagedSerializable<ManagedReference<Element<E>>>(null);
        ManagedSerializable<Long> tailCount =
                new ManagedSerializable<Long>(0L);


        headElement = dm.createReference(head);
        headCounter = dm.createReference(headCount);
        tailElement = dm.createReference(tail);
        tailCounter = dm.createReference(tailCount);
    }

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     *
     * @param e the new head {@code Element}.
     */
    private void addToHead(Element<E> e) {


        DataManager dm = AppContext.getDataManager();


        // short-circuit case if this element is the only element in
        // the deque (i.e. the deque was empty)
        if (headElement.get().get() == null) {
            ManagedReference<Element<E>> ref = dm.createReference(e);
            headElement.get().set(ref);
            tailElement.get().set(ref);
            return;
        }


        Element<E> oldHead = headElement();
        headElement.get().set(dm.createReference(e));
        e.setPrev(null);
        e.setNext(oldHead);
        oldHead.setPrev(e);
    }

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     *
     * @param e the new tail {@code Element}.
     */
    private void addToTail(Element<E> e) {


        DataManager dm = AppContext.getDataManager();


        // short-circuit case if this element is the only element in
        // the deque (i.e. the deque was empty)
        if (tailElement.get().get() == null) {
            ManagedReference<Element<E>> ref = dm.createReference(e);
            headElement.get().set(ref);
            tailElement.get().set(ref);
            return;
        }


        Element<E> oldTail = tailElement();
        tailElement.get().set(dm.createReference(e));
        e.setPrev(oldTail);
        e.setNext(null);
        oldTail.setNext(e);
    }

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        if (o == null || !(o instanceof ScalableDeque)) {
            return false;
        }
        ScalableDeque<E> d = uncheckedCast(o);
        DataManager dm = AppContext.getDataManager();
        return dm.createReference(this).equals(dm.createReference(d));
    }

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        // update the references to the front and back of the list, if
        // necessary.  We rely on the invariants that the previous and
        // next element references will only be null if an element is
        // at an end of the list.
        DataManager dm = AppContext.getDataManager();
        if (e.prevElement == null) {
            headElement.get().set((next == null)
                                  ? null : dm.createReference(next));
        }
        if (e.nextElement == null) {
            tailElement.get().set((prev == null)
                                  ? null : dm.createReference(prev));
        }
        AppContext.getDataManager().removeObject(e);


        return value;
    }

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     */
    public void removingObject() {
        clear();


        // Remove the ManagedSerializable objects as well
        DataManager dm = AppContext.getDataManager();
        dm.removeObject(backingMap);
        dm.removeObject(headElement.get());
        dm.removeObject(headCounter.get());
        dm.removeObject(tailElement.get());
        dm.removeObject(tailCounter.get());
    }

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