narya/src/java/com/threerings/presents/dobj/AttributeChangedEvent.java

//
// $Id$
//
// Narya library - tools for developing networked games
// Copyright (C) 2002-2004 Three Rings Design, Inc., All Rights Reserved
// http://www.threerings.net/code/narya/
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

package com.threerings.presents.dobj;

import java.lang.reflect.Array;

import java.util.HashMap;

import com.samskivert.util.StringUtil;

/**
 * An attribute changed event is dispatched when a single attribute of a
 * distributed object has changed. It can also be constructed to request
 * an attribute change on an object and posted to the dobjmgr.
 *
 * @see DObjectManager#postEvent
 */
public class AttributeChangedEvent extends NamedEvent
{
    /**
     * Constructs a blank instance of this event in preparation for
     * unserialization from the network.
     */
    public AttributeChangedEvent ()
    {
    }

    /**
     * Returns the new value of the attribute.
     */
    public Object getValue ()
    {
        return _value;
    }

    /**
     * Returns the value of the attribute prior to the application of this
     * event.
     */
    public Object getOldValue ()
    {
        return _oldValue;
    }

    /**
     * Returns the new value of the attribute as a short. This will fail
     * if the attribute in question is not a short.
     */
    public short getShortValue ()
    {
        return ((Short)_value).shortValue();
    }

    /**
     * Returns the new value of the attribute as an int. This will fail if
     * the attribute in question is not an int.
     */
    public int getIntValue ()
    {
        return ((Integer)_value).intValue();
    }

    /**
     * Returns the new value of the attribute as a long. This will fail if
     * the attribute in question is not a long.
     */
    public long getLongValue ()
    {
        return ((Long)_value).longValue();
    }

    /**
     * Returns the new value of the attribute as a float. This will fail
     * if the attribute in question is not a float.
     */
    public float getFloatValue ()
    {
        return ((Float)_value).floatValue();
    }

    /**
     * Returns the new value of the attribute as a double. This will fail
     * if the attribute in question is not a double.
     */
    public double getDoubleValue ()
    {
        return ((Double)_value).doubleValue();
    }

    /**
     * Applies this attribute change to the object.
     */
    public boolean applyToObject (DObject target)
        throws ObjectAccessException
    {
        // if we have no old value, that means we're not running on the
        // master server and we have not already applied this attribute
        // change to the object, so we must grab the previous value and
        // actually apply the attribute change
        if (_oldValue == UNSET_OLD_VALUE) {
            _oldValue = target.getAttribute(_name);
            Object value = _value;
            if (value != null) {
                Class vclass = value.getClass();
                if (vclass.isPrimitive()) {
                    // do nothing; we check this to avoid the more
                    // expensive isAssignableFrom check on primitives
                    // which are far and away the most common case
                } else if (vclass.isArray()) {
                    int length = Array.getLength(value);
                    Object clone = Array.newInstance(
                        vclass.getComponentType(), length);
                    System.arraycopy(value, 0, clone, 0, length);
                    value = clone;
                } else if (DSet.class.isAssignableFrom(vclass)) {
                    value = ((DSet)value).clone();
                }
            }
            // pass the new value on to the object
            target.setAttribute(_name, value);
        }
        return true;
    }

    /**
     * Constructs a new attribute changed event on the specified target
     * object with the supplied attribute name and value. <em>Do not
     * construct these objects by hand.</em> Use {@link
     * DObject#changeAttribute} instead.
     *
     * @param targetOid the object id of the object whose attribute has
     * changed.
     * @param name the name of the attribute (data member) that has
     * changed.
     * @param value the new value of the attribute (in the case of
     * primitive types, the reflection-defined object-alternative is
     * used).
     */
    protected AttributeChangedEvent (
        int targetOid, String name, Object value, Object oldValue)
    {
        super(targetOid, name);
        _value = value;
        _oldValue = oldValue;
    }

    // documentation inherited
    protected void notifyListener (Object listener)
    {
        if (listener instanceof AttributeChangeListener) {
            ((AttributeChangeListener)listener).attributeChanged(this);
        }
    }

    // documentation inherited
    protected void toString (StringBuffer buf)
    {
        buf.append("CHANGE:");
        super.toString(buf);
        buf.append(", value=");
        StringUtil.toString(buf, _value);
    }

    protected Object _value;
    protected transient Object _oldValue = UNSET_OLD_VALUE;
}