/*
 * Copyright 2010-2011 Ning, Inc.
 *
 * Ning 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 com.ning.billing.beatrix.bus.api;


/**
 * The interface {@code ExternalBus} represents the bus on which Killbill users can register handlers
 * to receive notifications when change happen in the system
 */
public interface ExternalBus {

    /**
     * Registers a callback.
     *
     * @param handlerInstance the handler that will be called back by the system when something changed
     */
    public void register(final Object handlerInstance); /* throws EventBusException */

    /**
     * Unregister a callback.
     *
     * @param handlerInstance the handler that was previously registered
     */
    public void unregister(final Object handlerInstance); /* throws EventBusException */
}
