examples/org.eclipse.ocl.examples.eventmanager/src/org/eclipse/ocl/examples/eventmanager/framework/EventAdapter.java

/*******************************************************************************
 * Copyright (c) 2009, 2018 SAP AG and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v2.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v20.html
 * 
 * Contributors:
 *     SAP AG - initial API and implementation
 ******************************************************************************/
package org.eclipse.ocl.examples.eventmanager.framework;

import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.WeakHashMap;

import org.eclipse.emf.common.notify.Notification;
import org.eclipse.emf.common.notify.Notifier;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.emf.ecore.resource.Resource;
import org.eclipse.emf.ecore.util.EContentAdapter;
import org.eclipse.ocl.examples.eventmanager.EventManager;


/**
 * This special {@link EContentAdapter} is used to notify a given {@link EventManager} if any notification is raised
 * ATTENTION: for the right registration at a target one have to use <code>target.eAdapters().add(myAdapter);</code>
 * 
 * @author Philipp Berger
 *
 */
public class EventAdapter extends EContentAdapter {
    private final WeakReference<EventManager> eventManager;
    private final Map<Notifier, Integer> alreadyRegisteredOn;

    /**
     * Constructs a new Adapter with the given {@link EventManager} as instance to notify
     * NOTE: the EventManager is held as {@link WeakReference}
     */
    public EventAdapter(EventManager eventManager) {
        this.eventManager = new WeakReference<EventManager>(eventManager);
        this.alreadyRegisteredOn = new WeakHashMap<Notifier, Integer>();
    }
    
    /**
     * Avoid duplicate adapter entry which would otherwise happen because objects may be "physically" contained in
     * a {@link Resource}'s {@link Resource#getContents() contents} but also be "logically" contained in another
     * {@link EObject} by means of a containment reference.
     */
    @Override
    protected void addAdapter(Notifier notifier) {
        if (!notifier.eAdapters().contains(this)) {
            notifier.eAdapters().add(this);
            alreadyRegisteredOn.put(notifier, 1);
        } else {
            alreadyRegisteredOn.put(notifier, alreadyRegisteredOn.get(notifier)+1);
        }
    }
    
    @Override
    protected void removeAdapter(Notifier notifier) {
        Integer count = alreadyRegisteredOn.get(notifier);
        if (count != null) {
            if (count > 1) {
                alreadyRegisteredOn.put(notifier, count-1);
            } else {
                alreadyRegisteredOn.remove(notifier);
                super.removeAdapter(notifier);
            }
        }
    }

    @Override
    public void notifyChanged(Notification notification) {
        super.notifyChanged(notification);
        EventManager m = this.eventManager.get();
        if (m!=null) {
            m.handleEMFEvent(notification);
        }
    }
}