    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.configuration2.builder;
    018
    019import java.util.Collections;
    020import java.util.Map;
    021
    022import org.apache.commons.configuration2.event.Event;
    023import org.apache.commons.configuration2.event.EventListener;
    024import org.apache.commons.configuration2.event.EventListenerList;
    025import org.apache.commons.configuration2.event.EventListenerRegistrationData;
    026import org.apache.commons.configuration2.event.EventType;
    027
    028/**
    029 * <p>
    030 * A specialized parameters implementation for {@link BasicConfigurationBuilder}
    031 * which allows for a convenient event listener initialization.
    032 * </p>
    033 * <p>
    034 * This class offers a fluent interface for registering event listeners. A fully
    035 * initialized instance can be passed to the
    036 * {@link BasicConfigurationBuilder#configure(BuilderParameters...)} method. All
    037 * event listeners which have been registered at the instance are then copied
    038 * over to the configuration builder.
    039 * </p>
    040 * <p>
    041 * The code fragment below shows a typical usage scenario:
    042 * </p>
    043 *
    044 * <pre>
    045 * BasicConfigurationBuilder&lt;Configuration&gt; builder =
    046 *         new BasicConfigurationBuilder&lt;Configuration&gt;(
    047 *                 PropertiesConfiguration.class)
    048 *                 .configure(new EventListenerParameters().addEventListener(
    049 *                         ConfigurationEvent.ANY, myListener));
    050 * </pre>
    051 *
    052 * <p>
    053 * In order to support a configuration builder's {@code configure()} method,
    054 * this class implements the {@code BuilderParameters} interface. However, this
    055 * is just a dummy implementation; no parameters are propagated to the builder.
    056 * </p>
    057 *
    058 * @since 2.0
    059 */
    060public class EventListenerParameters implements BuilderParameters,
    061        EventListenerProvider
    062{
    063    /** Stores the event listener registrations added to this object. */
    064    private final EventListenerList eventListeners;
    065
    066    /**
    067     * Creates a new instance of {@code EventListenerParameters}.
    068     */
    069    public EventListenerParameters()
    070    {
    071        eventListeners = new EventListenerList();
    072    }
    073
    074    /**
    075     * Adds an event listener of the specified event type to this object.
    076     *
    077     * @param eventType the event type object
    078     * @param listener the event listener
    079     * @param <T> the event type
    080     * @return a reference to this object for method chaining
    081     */
    082    public <T extends Event> EventListenerParameters addEventListener(
    083            final EventType<T> eventType, final EventListener<? super T> listener)
    084    {
    085        eventListeners.addEventListener(eventType, listener);
    086        return this;
    087    }
    088
    089    /**
    090     * Adds the specified {@code EventListenerRegistrationData} instance to this
    091     * object.
    092     *
    093     * @param registrationData the registration object to be added
    094     * @param <T> the event type of the contained event listener
    095     * @return a reference to this object for method chaining
    096     */
    097    public <T extends Event> EventListenerParameters addEventListener(
    098            final EventListenerRegistrationData<T> registrationData)
    099    {
    100        eventListeners.addEventListener(registrationData);
    101        return this;
    102    }
    103
    104    /**
    105     * {@inheritDoc} This implementation returns an empty map.
    106     */
    107    @Override
    108    public Map<String, Object> getParameters()
    109    {
    110        return Collections.emptyMap();
    111    }
    112
    113    @Override
    114    public EventListenerList getListeners()
    115    {
    116        return eventListeners;
    117    }
    118}