/*
 * 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.openjpa.lib.util;

import java.util.Collection;

/**
 * Basic event manager interface.
 *
 * @author Abe White
 */
public interface EventManager {

    /**
     * Add an event listener.
     */
    void addListener(Object listener);

    /**
     * Remove an event listener.
     */
    boolean removeListener(Object listener);

    /**
     * Return whether the given instance is in the list of listeners.
     */
    boolean hasListener(Object listener);

    /**
     * Return true if there are any registered listeners.
     */
    boolean hasListeners();

    /**
     * Return a read-only list of listeners.
     */
    Collection getListeners();

    /**
     * Fire the given event to all listeners, returning any exceptions.
     */
    Exception[] fireEvent(Object event);
}
