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Excalibur Event API

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/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.excalibur.event;

/**
 * A Source implements the side of an event queue where queue elements are
 * dequeued operations only.
 *
 * 
 *   The interface design is heavily influenced by
 *   Matt Welsh's SandStorm server,
 *   his demonstration of the SEDA architecture.  We have deviated where we
 *   felt the design differences where better.
 * 
 *
 * @author Avalon Development Team
 */
public interface Message
{
    /**
     * Get the attachment associated with this Message.  If there is no
     * attachment, this method will return null.
     *
     * @return Object the attached Object
     */
    Object getAttachment();

    /**
     * Attach an Object to the message.
     *
     * @param attachment  Any arbitrary Object you wish to attach to the Message
     */
    void attach( Object attachment );

    /**
     * Clear the attachment.
     */
    void clear();
}