MessageType.java

/*
 * Copyright (c) 2009, Paul Merlin. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
package org.swing.on.steroids.messagebus;

/**
 * Pivot of the MessageBus type safety.
 *
 * Each instance is backed by an integer used as its hashCode. A static integer, starting at 0
 * is incremented for each instance. This ties the MessageBus implementations into one jvm only.
 *
 * Bridging different buses can be done with one subscriber on each with care about failures.
 * TODO AntiCorruptionLayer
 *
 * @param <S> Subscriber mark
 */
@SuppressWarnings( "ValueOfIncrementOrDecrementUsed" )
public class MessageType<S extends Subscriber>
{

    private static int nextHashCode;
    private final int index;

    public MessageType()
    {
        super();
        index = ++nextHashCode;
    }

    // CHECKSTYLE:OFF equals is not implemented on purpose !
    @Override
    public final int hashCode()
    {
        // We override hash code to make it as efficient as possible
        return index;
    }
    // CHECKSTYLE:ON

}