CollectionValueModelWrapper.java

/*******************************************************************************
 * Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.uitools.app;


import java.util.Collection;
import java.util.Iterator;

import org.eclipse.persistence.tools.workbench.utility.AbstractModel;
import org.eclipse.persistence.tools.workbench.utility.events.ChangeSupport;
import org.eclipse.persistence.tools.workbench.utility.events.CollectionChangeEvent;
import org.eclipse.persistence.tools.workbench.utility.events.CollectionChangeListener;


/**
 * This abstract class provides the infrastructure needed to wrap
 * another collection value model, "lazily" listen to it, and propagate
 * its change notifications.
 */
public abstract class CollectionValueModelWrapper
    extends AbstractModel
    implements CollectionValueModel
{


    /** The wrapped collection value model. */
    protected CollectionValueModel collectionHolder;

    /** A listener that allows us to synch with changes to the wrapped collection holder. */
    protected CollectionChangeListener collectionChangeListener;


    // ********** constructors **********

    /**
     * Construct a collection value model with the specified wrapped
     * collection value model.
     */
    protected CollectionValueModelWrapper(CollectionValueModel collectionHolder) {
        super();
        this.collectionHolder = collectionHolder;
    }


    // ********** initialization **********

    protected void initialize() {
        super.initialize();
        this.collectionChangeListener = this.buildCollectionChangeListener();
    }

    /**
     * @see org.eclipse.persistence.tools.workbench.utility.AbstractModel#buildDefaultChangeSupport()
     */
    protected ChangeSupport buildDefaultChangeSupport() {
        return new ValueModelChangeSupport(this);
    }

    protected CollectionChangeListener buildCollectionChangeListener() {
        return new CollectionChangeListener() {
            public void itemsAdded(CollectionChangeEvent e) {
                CollectionValueModelWrapper.this.itemsAdded(e);
            }
            public void itemsRemoved(CollectionChangeEvent e) {
                CollectionValueModelWrapper.this.itemsRemoved(e);
            }
            public void collectionChanged(CollectionChangeEvent e) {
                CollectionValueModelWrapper.this.collectionChanged(e);
            }
            public String toString() {
                return "collection change listener";
            }
        };
    }


    // ********** extend change support **********

    /**
     * Extend to start listening to the nested model if necessary.
     * @see Model#addCollectionChangeListener(CollectionChangeListener)
     */
    public synchronized void addCollectionChangeListener(CollectionChangeListener listener) {
        if (this.hasNoCollectionChangeListeners(VALUE)) {
            this.engageModel();
        }
        super.addCollectionChangeListener(listener);
    }

    /**
     * Extend to start listening to the nested model if necessary.
     * @see Model#addCollectionChangeListener(String, CollectionChangeListener)
     */
    public synchronized void addCollectionChangeListener(String collectionName, CollectionChangeListener listener) {
        if (collectionName == VALUE && this.hasNoCollectionChangeListeners(VALUE)) {
            this.engageModel();
        }
        super.addCollectionChangeListener(collectionName, listener);
    }

    /**
     * Extend to stop listening to the nested model if necessary.
     * @see Model#removeCollectionChangeListener(CollectiontChangeListener)
     */
    public synchronized void removeCollectionChangeListener(CollectionChangeListener listener) {
        super.removeCollectionChangeListener(listener);
        if (this.hasNoCollectionChangeListeners(VALUE)) {
            this.disengageModel();
        }
    }

    /**
     * Extend to stop listening to the nested model if necessary.
     * @see Model#removeCollectionChangeListener(String, CollectionChangeListener)
     */
    public synchronized void removeCollectionChangeListener(String collectionName, CollectionChangeListener listener) {
        super.removeCollectionChangeListener(collectionName, listener);
        if (collectionName == VALUE && this.hasNoCollectionChangeListeners(VALUE)) {
            this.disengageModel();
        }
    }


    // ********** CollectionValueModel implementation **********

    /**
     * wrappers cannot be modified - the underlying model must be modified directly
     * @see CollectionValueModel#addItem(Object)
     */
    public void addItem(Object item) {
        throw new UnsupportedOperationException();
    }

    /**
     * @see CollectionValueModel#addItems(java.util.Collection)
     */
    public void addItems(Collection items) {
        for (Iterator stream = items.iterator(); stream.hasNext(); ) {
            this.addItem(stream.next());
        }
    }

    /**
     * wrappers cannot be modified - the underlying model must be modified directly
     * @see CollectionValueModel#removeItem(Object)
     */
    public void removeItem(Object item) {
        throw new UnsupportedOperationException();
    }

    /**
     * @see CollectionValueModel#removeItems(java.util.Collection)
     */
    public void removeItems(Collection items) {
        for (Iterator stream = items.iterator(); stream.hasNext(); ) {
            this.removeItem(stream.next());
        }
    }


    // ********** behavior **********

    /**
     * Start listening to the collection holder.
     */
    protected void engageModel() {
        this.collectionHolder.addCollectionChangeListener(VALUE, this.collectionChangeListener);
    }

    /**
     * Stop listening to the collection holder.
     */
    protected void disengageModel() {
        this.collectionHolder.removeCollectionChangeListener(VALUE, this.collectionChangeListener);
    }

    /**
     * @see org.eclipse.persistence.tools.workbench.framework.tools.AbstractModel#toString(StringBuffer)
     */
    public void toString(StringBuffer sb) {
        sb.append(this.collectionHolder);
    }


    // ********** collection change support **********

    /**
     * Items were added to the wrapped collection holder;
     * propagate the change notification appropriately.
     */
    protected abstract void itemsAdded(CollectionChangeEvent e);

    /**
     * Items were removed from the wrapped collection holder;
     * propagate the change notification appropriately.
     */
    protected abstract void itemsRemoved(CollectionChangeEvent e);

    /**
     * The value of the wrapped collection holder has changed;
     * propagate the change notification appropriately.
     */
    protected abstract void collectionChanged(CollectionChangeEvent e);

}