ListValueModelWrapper.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 org.eclipse.persistence.tools.workbench.utility.AbstractModel;
import org.eclipse.persistence.tools.workbench.utility.events.ChangeSupport;
import org.eclipse.persistence.tools.workbench.utility.events.ListChangeEvent;
import org.eclipse.persistence.tools.workbench.utility.events.ListChangeListener;


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

    /** The wrapped list value model. */
    protected ListValueModel listHolder;

    /** A listener that allows us to synch with changes to the wrapped list holder. */
    protected ListChangeListener listChangeListener;


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

    /**
     * Construct a list value model with the specified wrapped
     * list value model.
     */
    protected ListValueModelWrapper(ListValueModel listHolder) {
        super();
        if (listHolder == null) {
            throw new NullPointerException();
        }
        this.listHolder = listHolder;
    }


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

    protected void initialize() {
        super.initialize();
        this.listChangeListener = this.buildListChangeListener();
    }

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

    protected ListChangeListener buildListChangeListener() {
        return new ListChangeListener() {
            public void itemsAdded(ListChangeEvent e) {
                ListValueModelWrapper.this.itemsAdded(e);
            }
            public void itemsRemoved(ListChangeEvent e) {
                ListValueModelWrapper.this.itemsRemoved(e);
            }
            public void itemsReplaced(ListChangeEvent e) {
                ListValueModelWrapper.this.itemsReplaced(e);
            }
            public void listChanged(ListChangeEvent e) {
                ListValueModelWrapper.this.listChanged(e);
            }
            public String toString() {
                return "list change listener";
            }
        };
    }


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

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

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

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

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


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

    /**
     * Start listening to the list holder.
     */
    protected void engageModel() {
        this.listHolder.addListChangeListener(VALUE, this.listChangeListener);
    }

    /**
     * Stop listening to the list holder.
     */
    protected void disengageModel() {
        this.listHolder.removeListChangeListener(VALUE, this.listChangeListener);
    }

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


    // ********** list change support **********

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

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

    /**
     * Items were replaced in the wrapped list holder;
     * propagate the change notification appropriately.
     */
    protected abstract void itemsReplaced(ListChangeEvent e);

    /**
     * The value of the wrapped list holder has changed;
     * propagate the change notification appropriately.
     */
    protected abstract void listChanged(ListChangeEvent e);

}