001/* 002 * GWTEventService 003 * Copyright (c) 2011 and beyond, strawbill UG (haftungsbeschr?nkt) 004 * 005 * This is free software; you can redistribute it and/or modify it 006 * under the terms of the GNU Lesser General Public License as 007 * published by the Free Software Foundation; either version 3 of 008 * the License, or (at your option) any later version. 009 * Other licensing for GWTEventService may also be possible on request. 010 * Please view the license.txt of the project for more information. 011 * 012 * This software is distributed in the hope that it will be useful, 013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 015 * Lesser General Public License for more details. 016 * 017 * You should have received a copy of the GNU Lesser General Public 018 * License along with this software; if not, write to the Free 019 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 020 * 02110-1301 USA, or see the FSF site: http://www.fsf.org. 021 */ 022package de.novanic.eventservice.client.event.filter; 023 024import de.novanic.eventservice.client.event.Event; 025 026/** 027 * Default implementation of the {@link de.novanic.eventservice.client.event.filter.EventFilter} interface. 028 * When no {@link de.novanic.eventservice.client.event.filter.EventFilter} is attached to the DefaultEventFilter, 029 * the DefaultEventFilter doesn't filter any events, because the match method returns false. An optional 030 * {@link de.novanic.eventservice.client.event.filter.EventFilter} instance can be attached using 031 * {@link de.novanic.eventservice.client.event.filter.AppendableEventFilter#attach(EventFilter)} or the constructor 032 * {@link de.novanic.eventservice.client.event.filter.DefaultEventFilter#DefaultEventFilter(EventFilter)} and is used/called 033 * by the default implementation of the match method of DefaultEventFilter. The DefaultEventFilter implements the 034 * {@link de.novanic.eventservice.client.event.filter.CascadingEventFilter} interface to allow to build cascading filter 035 * sequences. A CascadingEventFilter can only hold one (the next) {@link de.novanic.eventservice.client.event.filter.EventFilter}. 036 * See {@link de.novanic.eventservice.client.event.filter.CascadingEventFilter} for more information. 037 * 038 * @author sstrohschein 039 * <br>Date: 20.07.2008 040 * <br>Time: 15:33:39 041 */ 042public class DefaultEventFilter implements CascadingEventFilter 043{ 044 private EventFilter myNextEventFilter; 045 046 /** 047 * Creates a new DefaultEventFilter. An optional, appended {@link de.novanic.eventservice.client.event.filter.EventFilter} can 048 * be set/attached with {@link de.novanic.eventservice.client.event.filter.AppendableEventFilter#attach(EventFilter)} or 049 * the constructor {@link de.novanic.eventservice.client.event.filter.DefaultEventFilter#DefaultEventFilter(EventFilter)}. 050 */ 051 public DefaultEventFilter() {} 052 053 /** 054 * Creates a new DefaultEventFilter. The {@link de.novanic.eventservice.client.event.filter.EventFilter} is used by 055 * the default implementation of the match method (in DefaultEventFilter) to filter the events. 056 * @param aNextEventFilter {@link de.novanic.eventservice.client.event.filter.EventFilter} to attach 057 */ 058 public DefaultEventFilter(EventFilter aNextEventFilter) { 059 attach(aNextEventFilter); 060 } 061 062 /** 063 * When no {@link de.novanic.eventservice.client.event.filter.EventFilter} is attached to the DefaultEventFilter, 064 * no events will be filtered, because that method implementation returns false. An optional 065 * {@link de.novanic.eventservice.client.event.filter.EventFilter} instance can be attached using 066 * {@link de.novanic.eventservice.client.event.filter.AppendableEventFilter#attach(EventFilter)} or the constructor 067 * {@link de.novanic.eventservice.client.event.filter.DefaultEventFilter#DefaultEventFilter(EventFilter)}. 068 * @param anEvent event 069 * @return false or the result of the optional, attached {@link de.novanic.eventservice.client.event.filter.EventFilter} 070 */ 071 public boolean match(Event anEvent) { 072 return myNextEventFilter != null && myNextEventFilter.match(anEvent); 073 } 074 075 /** 076 * Sets/Attaches another {@link de.novanic.eventservice.client.event.filter.EventFilter} which is used/called from the match method 077 * ({@link de.novanic.eventservice.client.event.filter.EventFilter#match(de.novanic.eventservice.client.event.Event)}). 078 * A CascadingEventFilter can only hold one {@link de.novanic.eventservice.client.event.filter.EventFilter}. 079 * @param anEventFilter {@link de.novanic.eventservice.client.event.filter.EventFilter} to attach/set 080 * @return itself/DefaultEventFilter (result of the attachment) 081 */ 082 public AppendableEventFilter attach(EventFilter anEventFilter) { 083 myNextEventFilter = anEventFilter; 084 return this; 085 } 086 087 /** 088 * Detaches the attached {@link de.novanic.eventservice.client.event.filter.EventFilter}. A CascadingEventFilter can 089 * only hold one {@link de.novanic.eventservice.client.event.filter.EventFilter}. 090 * EventFilter instances can be attached with {@link de.novanic.eventservice.client.event.filter.AppendableEventFilter#attach(EventFilter)}. 091 * @return true if an EventFilter was registered, otherwise false 092 */ 093 public boolean detach() { 094 if(myNextEventFilter != null) { 095 myNextEventFilter = null; 096 return true; 097 } 098 return false; 099 } 100 101 /** 102 * Returns the attached EventFilter. A CascadingEventFilter can only hold one {@link de.novanic.eventservice.client.event.filter.EventFilter}. 103 * EventFilter instances can be attached with {@link de.novanic.eventservice.client.event.filter.AppendableEventFilter#attach(EventFilter)}. 104 * @return the attached {@link de.novanic.eventservice.client.event.filter.EventFilter} 105 */ 106 public EventFilter getAttachedEventFilter() { 107 return myNextEventFilter; 108 } 109}