200 lines
6.4 KiB
Java
200 lines
6.4 KiB
Java
/*
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* WorldEdit, a Minecraft world manipulation toolkit
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* Copyright (C) sk89q <http://www.sk89q.com>
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* Copyright (C) WorldEdit team and contributors
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package com.sk89q.worldedit.util.eventbus;
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import com.google.common.collect.HashMultimap;
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import com.google.common.collect.Multimap;
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import com.google.common.collect.SetMultimap;
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import com.sk89q.worldedit.internal.util.LogManagerCompat;
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import org.apache.logging.log4j.Logger;
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import java.lang.reflect.InvocationTargetException;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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import java.util.concurrent.locks.ReadWriteLock;
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import java.util.concurrent.locks.ReentrantReadWriteLock;
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import static com.google.common.base.Preconditions.checkNotNull;
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/**
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* Dispatches events to listeners, and provides ways for listeners to register
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* themselves.
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*
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* <p>This class is based on Guava's {@link EventBus} but priority is supported
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* and events are dispatched at the time of call, rather than being queued up.
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* This does allow dispatching during an in-progress dispatch.</p>
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*/
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public final class EventBus {
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private static final Logger LOGGER = LogManagerCompat.getLogger();
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private final ReadWriteLock lock = new ReentrantReadWriteLock();
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private final SetMultimap<Class<?>, EventHandler> handlersByType =
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HashMultimap.create();
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/**
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* Strategy for finding handler methods in registered objects. Currently,
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* only the {@link AnnotatedSubscriberFinder} is supported, but this is
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* encapsulated for future expansion.
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*/
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private final SubscriberFindingStrategy finder = new AnnotatedSubscriberFinder();
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private HierarchyCache flattenHierarchyCache = new HierarchyCache();
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/**
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* Registers the given handler for the given class to receive events.
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*
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* @param clazz the event class to register
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* @param handler the handler to register
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*/
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public void subscribe(Class<?> clazz, EventHandler handler) {
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checkNotNull(clazz);
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checkNotNull(handler);
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lock.writeLock().lock();
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try {
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handlersByType.put(clazz, handler);
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} finally {
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lock.writeLock().unlock();
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}
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}
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/**
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* Registers the given handler for the given class to receive events.
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*
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* @param handlers a map of handlers
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*/
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public void subscribeAll(Multimap<Class<?>, EventHandler> handlers) {
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checkNotNull(handlers);
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lock.writeLock().lock();
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try {
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handlersByType.putAll(handlers);
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} finally {
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lock.writeLock().unlock();
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}
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}
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/**
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* Unregisters the given handler for the given class.
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*
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* @param clazz the class
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* @param handler the handler
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*/
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public void unsubscribe(Class<?> clazz, EventHandler handler) {
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checkNotNull(clazz);
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checkNotNull(handler);
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lock.writeLock().lock();
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try {
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handlersByType.remove(clazz, handler);
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} finally {
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lock.writeLock().unlock();
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}
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}
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/**
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* Unregisters the given handlers.
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*
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* @param handlers a map of handlers
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*/
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public void unsubscribeAll(Multimap<Class<?>, EventHandler> handlers) {
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checkNotNull(handlers);
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lock.writeLock().lock();
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try {
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for (Map.Entry<Class<?>, Collection<EventHandler>> entry : handlers.asMap().entrySet()) {
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handlersByType.get(entry.getKey()).removeAll(entry.getValue());
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}
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} finally {
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lock.writeLock().unlock();
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}
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}
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/**
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* Registers all handler methods on {@code object} to receive events.
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* Handler methods are selected and classified using this EventBus's
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* {@link SubscriberFindingStrategy}; the default strategy is the
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* {@link AnnotatedSubscriberFinder}.
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*
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* @param object object whose handler methods should be registered.
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*/
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public void register(Object object) {
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subscribeAll(finder.findAllSubscribers(object));
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}
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/**
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* Unregisters all handler methods on a registered {@code object}.
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*
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* @param object object whose handler methods should be unregistered.
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* @throws IllegalArgumentException if the object was not previously registered.
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*/
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public void unregister(Object object) {
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unsubscribeAll(finder.findAllSubscribers(object));
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}
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/**
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* Posts an event to all registered handlers. This method will return
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* successfully after the event has been posted to all handlers, and
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* regardless of any exceptions thrown by handlers.
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*
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* @param event event to post.
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*/
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public void post(Object event) {
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List<EventHandler> dispatching = new ArrayList<>();
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Set<Class<?>> dispatchTypes = flattenHierarchyCache.get(event.getClass());
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lock.readLock().lock();
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try {
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for (Class<?> eventType : dispatchTypes) {
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Set<EventHandler> wrappers = handlersByType.get(eventType);
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if (wrappers != null && !wrappers.isEmpty()) {
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dispatching.addAll(wrappers);
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}
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}
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} finally {
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lock.readLock().unlock();
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}
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Collections.sort(dispatching);
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for (EventHandler handler : dispatching) {
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dispatch(event, handler);
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}
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}
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/**
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* Dispatches {@code event} to the handler in {@code handler}.
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*
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* @param event event to dispatch.
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* @param handler handler that will call the handler.
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*/
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private void dispatch(Object event, EventHandler handler) {
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try {
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handler.handleEvent(event);
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} catch (InvocationTargetException e) {
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LOGGER.error("Could not dispatch event: " + event + " to handler " + handler, e);
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}
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}
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}
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