001/*
002 * JGrapes Event Driven Framework
003 * Copyright (C) 2016-2018 Michael N. Lipp
004 * 
005 * This program is free software; you can redistribute it and/or modify it 
006 * under the terms of the GNU Affero General Public License as published by 
007 * the Free Software Foundation; either version 3 of the License, or 
008 * (at your option) any later version.
009 * 
010 * This program is distributed in the hope that it will be useful, but 
011 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
012 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License 
013 * for more details.
014 * 
015 * You should have received a copy of the GNU Affero General Public License along 
016 * with this program; if not, see <http://www.gnu.org/licenses/>.
017 */
018
019package org.jgrapes.core;
020
021import org.jgrapes.core.annotation.ComponentManager;
022
023/**
024 * This interface marks a class as a component. Implementing this interface is 
025 * an alternative to deriving from {@link Component} (usually because 
026 * there is some other preferential inheritance relationship). 
027 * Components that implement this interface (but don't inherit from
028 * {@link Component}) aren't inserted as vertices into the component tree;
029 * rather, they are represented in the tree by a proxy. 
030 * 
031 * Classes that implement {@code ComponentType} aren't required to
032 * implement specific methods. They must, however, declare a field
033 * for a component manager. This field must be of type 
034 * {@link Manager} and annotated as {@link ComponentManager}.
035 * The implementation of the component type can use the value in this 
036 * field to get access to the component hierarchy. The field is initialized
037 * when the component type is added to the component hierarchy or when
038 * calling {@link Components#manager(ComponentType)} or
039 * {@link Components#manager(ComponentType, Channel)}.
040 * 
041 * The channel associated with an instance of {@link ComponentType}
042 * can be specified as attribute of the {@link ComponentManager}
043 * annotation. If no channel is specified, the proxy is used as
044 * channel (see {@link Channel#SELF}). The default can be overridden
045 * on a per instance basis by calling 
046 * {@link Components#manager(ComponentType, Channel)} before the component
047 * is added to the tree.
048 */
049public interface ComponentType {
050
051}