/*
* Copyright 2011 Google Inc.
*
* Licensed 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 com.google.web.bindery.event.shared;
import com.google.web.bindery.event.shared.Event.Type;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Set;
/**
* Basic implementation of {@link EventBus}.
*/
public class SimpleEventBus extends EventBus {
private interface Command {
void execute();
}
private final boolean isReverseOrder;
private int firingDepth = 0;
/**
* Add and remove operations received during dispatch.
*/
private List<Command> deferredDeltas;
/**
* Map of event type to map of event source to list of their handlers.
*/
private final Map<Event.Type<?>, Map<Object, List<?>>> map =
new HashMap<Event.Type<?>, Map<Object, List<?>>>();
public SimpleEventBus() {
this(false);
}
/**
* Allows creation of an instance that fires its handlers in the reverse of
* the order in which they were added, although filtered handlers all fire
* before unfiltered handlers.
* <p>
*
* @deprecated This is a legacy feature, required by GWT's old HandlerManager.
* Reverse order is not honored for handlers tied to a specific
* event source (via {@link #addHandlerToSource}.
*/
@Deprecated
protected SimpleEventBus(boolean fireInReverseOrder) {
isReverseOrder = fireInReverseOrder;
}
@Override
public <H> HandlerRegistration addHandler(Type<H> type, H handler) {
return doAdd(type, null, handler);
}
@Override
public <H> HandlerRegistration addHandlerToSource(final Event.Type<H> type, final Object source,
final H handler) {
if (source == null) {
throw new NullPointerException("Cannot add a handler with a null source");
}
return doAdd(type, source, handler);
}
@Override
public void fireEvent(Event<?> event) {
doFire(event, null);
}
@Override
public void fireEventFromSource(Event<?> event, Object source) {
if (source == null) {
throw new NullPointerException("Cannot fire from a null source");
}
doFire(event, source);
}
/**
* @deprecated required by legacy features in GWT's old HandlerManager
*/
@Deprecated
protected <H> void doRemove(Event.Type<H> type, Object source, H handler) {
if (firingDepth > 0) {
enqueueRemove(type, source, handler);
} else {
doRemoveNow(type, source, handler);
}
}
/**
* @deprecated required by legacy features in GWT's old HandlerManager
*/
@Deprecated
protected <H> H getHandler(Event.Type<H> type, int index) {
assert index < getHandlerCount(type) : "handlers for " + type.getClass() + " have size: "
+ getHandlerCount(type) + " so do not have a handler at index: " + index;
List<H> l = getHandlerList(type, null);
return l.get(index);
}
/**
* @deprecated required by legacy features in GWT's old HandlerManager
*/
@Deprecated
protected int getHandlerCount(Event.Type<?> eventKey) {
return getHandlerList(eventKey, null).size();
}
/**
* @deprecated required by legacy features in GWT's old HandlerManager
*/
@Deprecated
protected boolean isEventHandled(Event.Type<?> eventKey) {
return map.containsKey(eventKey);
}
private void defer(Command command) {
if (deferredDeltas == null) {
deferredDeltas = new ArrayList<Command>();
}
deferredDeltas.add(command);
}
private <H> HandlerRegistration doAdd(final Event.Type<H> type, final Object source,
final H handler) {
if (type == null) {
throw new NullPointerException("Cannot add a handler with a null type");
}
if (handler == null) {
throw new NullPointerException("Cannot add a null handler");
}
if (firingDepth > 0) {
enqueueAdd(type, source, handler);
} else {
doAddNow(type, source, handler);
}
return new HandlerRegistration() {
public void removeHandler() {
doRemove(type, source, handler);
}
};
}
private <H> void doAddNow(Event.Type<H> type, Object source, H handler) {
List<H> l = ensureHandlerList(type, source);
l.add(handler);
}
private <H> void doFire(Event<H> event, Object source) {
if (event == null) {
throw new NullPointerException("Cannot fire null event");
}
try {
firingDepth++;
if (source != null) {
setSourceOfEvent(event, source);
}
List<H> handlers = getDispatchList(event.getAssociatedType(), source);
Set<Throwable> causes = null;
ListIterator<H> it =
isReverseOrder ? handlers.listIterator(handlers.size()) : handlers.listIterator();
while (isReverseOrder ? it.hasPrevious() : it.hasNext()) {
H handler = isReverseOrder ? it.previous() : it.next();
try {
dispatchEvent(event, handler);
} catch (Throwable e) {
if (causes == null) {
causes = new HashSet<Throwable>();
}
causes.add(e);
}
}
if (causes != null) {
throw new UmbrellaException(causes);
}
} finally {
firingDepth--;
if (firingDepth == 0) {
handleQueuedAddsAndRemoves();
}
}
}
private <H> void doRemoveNow(Event.Type<H> type, Object source, H handler) {
List<H> l = getHandlerList(type, source);
boolean removed = l.remove(handler);
assert removed : "redundant remove call";
if (removed && l.isEmpty()) {
prune(type, source);
}
}
private <H> void enqueueAdd(final Event.Type<H> type, final Object source, final H handler) {
defer(new Command() {
public void execute() {
doAddNow(type, source, handler);
}
});
}
private <H> void enqueueRemove(final Event.Type<H> type, final Object source, final H handler) {
defer(new Command() {
public void execute() {
doRemoveNow(type, source, handler);
}
});
}
private <H> List<H> ensureHandlerList(Event.Type<H> type, Object source) {
Map<Object, List<?>> sourceMap = map.get(type);
if (sourceMap == null) {
sourceMap = new HashMap<Object, List<?>>();
map.put(type, sourceMap);
}
// safe, we control the puts.
@SuppressWarnings("unchecked")
List<H> handlers = (List<H>) sourceMap.get(source);
if (handlers == null) {
handlers = new ArrayList<H>();
sourceMap.put(source, handlers);
}
return handlers;
}
private <H> List<H> getDispatchList(Event.Type<H> type, Object source) {
List<H> directHandlers = getHandlerList(type, source);
if (source == null) {
return directHandlers;
}
List<H> globalHandlers = getHandlerList(type, null);
List<H> rtn = new ArrayList<H>(directHandlers);
rtn.addAll(globalHandlers);
return rtn;
}
private <H> List<H> getHandlerList(Event.Type<H> type, Object source) {
Map<Object, List<?>> sourceMap = map.get(type);
if (sourceMap == null) {
return Collections.emptyList();
}
// safe, we control the puts.
@SuppressWarnings("unchecked")
List<H> handlers = (List<H>) sourceMap.get(source);
if (handlers == null) {
return Collections.emptyList();
}
return handlers;
}
private void handleQueuedAddsAndRemoves() {
if (deferredDeltas != null) {
try {
for (Command c : deferredDeltas) {
c.execute();
}
} finally {
deferredDeltas = null;
}
}
}
private void prune(Event.Type<?> type, Object source) {
Map<Object, List<?>> sourceMap = map.get(type);
List<?> pruned = sourceMap.remove(source);
assert pruned != null : "Can't prune what wasn't there";
assert pruned.isEmpty() : "Pruned unempty list!";
if (sourceMap.isEmpty()) {
map.remove(type);
}
}
}