| /* |
| * 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.commons.configuration2.event; |
| |
| /** |
| * <p> |
| * An interface for configuration implementations which support registration of |
| * event listeners. |
| * </p> |
| * <p> |
| * Through the methods provided by this interface it is possible to register and |
| * remove listeners for different events supported by this library. The event |
| * type to be handled by a listener must be provided; the specified event listener |
| * must be compatible with this event type. By using generic type parameters, the |
| * compiler can check this. |
| * </p> |
| * |
| * @version $Id$ |
| * @since 2.0 |
| */ |
| public interface EventSource |
| { |
| /** |
| * Adds an event listener for the specified event type. This listener is |
| * notified about events of this type and all its sub types. |
| * |
| * @param eventType the event type (must not be <b>null</b>) |
| * @param listener the listener to be registered (must not be <b>null</b>) |
| * @param <T> the type of events processed by this listener |
| * @throws IllegalArgumentException if a required parameter is <b>null</b> |
| */ |
| <T extends Event> void addEventListener(EventType<T> eventType, |
| EventListener<? super T> listener); |
| |
| /** |
| * Removes the event listener registration for the given event type and |
| * listener. An event listener instance may be registered multiple times for |
| * different event types. Therefore, when removing a listener the event type |
| * of the registration in question has to be specified. The return value |
| * indicates whether a registration was removed. A value of <b>false</b> |
| * means that no such combination of event type and listener was found. |
| * |
| * @param eventType the event type |
| * @param listener the event listener to be removed |
| * @param <T> the type of events processed by this listener |
| * @return a flag whether a listener registration was removed |
| */ |
| <T extends Event> boolean removeEventListener(EventType<T> eventType, |
| EventListener<? super T> listener); |
| } |