SerializableEnumeration.java

/*
 Violet - A program for editing UML diagrams.

 Copyright (C) 2007 Cay S. Horstmann (http://horstmann.com)
 Alexandre de Pellegrin (http://alexdp.free.fr);

 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.

 This program 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 General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package com.horstmann.violet.framework.util;

import java.io.ObjectStreamException;
import java.io.Serializable;
import java.lang.reflect.Field;

import com.thoughtworks.xstream.annotations.XStreamAsAttribute;

/**
 * This class is a superclass for enumerated types that can be serialized. Subclass like this:
 * 
 * <pre>
 *   public class MyEnumeration extends SerializableEnumeration
 *   {
 *   private MyEnumeration() {}
 *   public static final MyEnumeration FOO = new MyEnumeration();
 *   public static final MyEnumeration BAR = new MyEnumeration();
 *   . . .
 *   }
 * </pre>
 * 
 * This defines instances <code>MyEnumeration.FOO</code> and <code>MyEnumeration.BAR</code> that are guaranteed to be preserved
 * through serialization and deserialization. Conveniently, the toString method yields the name (such as
 * <code>"FOO"<code>).
 */
public class SerializableEnumeration implements Serializable
{
    protected Object writeReplace() throws ObjectStreamException
    {
        if (name == null) toString();
        if (name == null) throw new ObjectStreamException("No matching field")
        {
        };
        return this;
    }

    public String toString()
    {
        if (name != null) return getClass().getName() + "." + name;
        try
        {
            Field[] fields = getClass().getFields();
            for (int i = 0; i < fields.length; i++)
            {
                if (fields[i].get(this) == this)
                {
                    name = fields[i].getName();
                    return toString();
                }
            }
        }
        catch (IllegalAccessException ex)
        {
        }
        return super.toString();
    }

    protected Object readResolve() throws ObjectStreamException
    {
        try
        {
            return getClass().getField(name).get(null);
        }
        catch (IllegalAccessException ex)
        {
        }
        catch (NoSuchFieldException ex)
        {
        }
        throw new ObjectStreamException("No matching field")
        {
        };
    }

    @XStreamAsAttribute
    private String name;
}