org.teamapps.event.Event Maven / Gradle / Ivy
/*-
* ========================LICENSE_START=================================
* TeamApps
* ---
* Copyright (C) 2014 - 2023 TeamApps.org
* ---
* 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.
* =========================LICENSE_END==================================
*/
package org.teamapps.event;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.teamapps.ux.session.CurrentSessionContext;
import org.teamapps.ux.session.SessionContext;
import java.lang.ref.WeakReference;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;
import java.util.function.Function;
/**
* Represents an event that can get fired.
*
* Listeners can be added to this event using the various {@link #addListener(Consumer) addListener(...)} methods.
*
*
SessionContext-bound Event Listeners
* Note that if a listener L is added while the thread is bound to a {@link SessionContext} A (so while {@link SessionContext#currentOrNull()} is not null),
* L's execution will be bound to A by default, i.e.:
*
* - When this event fires, the SessionContext-bound listener will get invoked bound to the SessionContext
A,
* regardless of the SessionContext (or the lack of it) the event was fired in.
* - When the SessionContext
A is destroyed (and thereby fires its {@link SessionContext#onDestroyed} event), the listener is automatically detached from this event.
*
* You can prevent a listener from being bound to the current SessionContext,
* by using one of the {@link #addListener(Consumer, boolean) addListener(..., boolean bindToSessionContext)} methods.
*
* @param The type of data this event fires.
*/
public class Event {
private static final Logger LOGGER = LoggerFactory.getLogger(Event.class);
private final String source; // for debugging
private final List> listeners = new CopyOnWriteArrayList<>();
private EVENT_DATA lastEventData;
public Event() {
StackTraceElement stackTraceElement = new Exception().getStackTrace()[1];
this.source = stackTraceElement.getFileName() + stackTraceElement.getLineNumber();
}
public Disposable addListener(Consumer listener) {
return addListener(listener, true);
}
public Disposable addListener(Consumer listener, boolean bindToSessionContext) {
SessionContext currentSessionContext;
if (bindToSessionContext && (currentSessionContext = CurrentSessionContext.getOrNull()) != null) {
listeners.add(new SessionContextAwareEventListener<>(currentSessionContext, listener));
removeWhenSessionDestroyed(listener, currentSessionContext);
} else {
// just add the listener. It will get called with whatever context is active at firing time
listeners.add(listener);
}
return () -> removeListener(listener);
}
public Disposable addListener(SelfDisposingEventListener listener) {
return addListener(listener, true);
}
public Disposable addListener(SelfDisposingEventListener listener, boolean bindToSessionContext) {
AtomicReference disposable = new AtomicReference<>();
disposable.set(addListener(e -> {
listener.handle(e, disposable.get());
}, bindToSessionContext));
return disposable.get();
}
public Disposable addListener(Runnable listener) {
return addListener(listener, true);
}
public Disposable addListener(Runnable listener, boolean bindToSessionContext) {
return addListener(new RunnableWrapper<>(listener), bindToSessionContext);
}
List> getListeners() {
return listeners;
}
/**
* @deprecated Use the {@link Disposable} returned by {@link #addListener(Runnable)} instead!
*/
@Deprecated
public void removeListener(Runnable listener) {
removeListener(new RunnableWrapper<>(listener));
}
/**
* @deprecated Use the {@link Disposable} returned by {@link #addListener(Consumer)} instead!
*/
@Deprecated
public void removeListener(Consumer listener) {
listeners.remove(listener); // in case it is not bound to a session
listeners.remove(new SessionContextAwareEventListener<>(listener));
}
/**
* When the session gets destroyed, remove this listener (preventing memory-leaks and degrading performance due to stale listeners).
*/
private void removeWhenSessionDestroyed(Consumer listener, SessionContext currentSessionContext) {
if (this != currentSessionContext.onDestroyed) { // prevent infinite recursion!
// use a weak reference here, so the fact that this is registered to the sessionContext's destroyed event
// does not mean it has to survive (not being garbage collected) as long as the session context.
WeakReference> listenerWeakReference = new WeakReference<>(listener);
currentSessionContext.onDestroyed.listeners.add(aVoid -> {
Consumer l = listenerWeakReference.get();
if (l != null) {
removeListener(l);
}
});
}
}
public void fire(EVENT_DATA eventData) {
this.lastEventData = eventData;
for (Consumer listener : listeners) {
invokeListener(eventData, listener);
}
}
public void fireIgnoringExceptions(EVENT_DATA eventData) {
this.lastEventData = eventData;
for (Consumer listener : listeners) {
try {
invokeListener(eventData, listener);
} catch (Exception e) {
LOGGER.error("Error while calling event handler. Ignoring exception.", e);
}
}
}
/**
* May get overridden.
*/
protected void invokeListener(EVENT_DATA eventData, Consumer listener) {
listener.accept(eventData);
}
public void fire() {
fire(null);
}
public void fireIfChanged(EVENT_DATA eventData) {
if (!Objects.equals(lastEventData, eventData)) {
fire(eventData);
}
}
public Event converted(Function converter) {
Event newEvent = new Event<>();
addListener(data -> newEvent.fire(converter.apply(data)));
return newEvent;
}
private static class SessionContextAwareEventListener implements Consumer {
private final SessionContext sessionContext;
private final Consumer delegate;
public SessionContextAwareEventListener(SessionContext sessionContext, Consumer delegate) {
this.sessionContext = sessionContext;
this.delegate = delegate;
}
public SessionContextAwareEventListener(Consumer delegate) {
this(null, delegate);
}
@Override
public void accept(EVENT_DATA eventData) {
if (sessionContext != null) {
sessionContext.runWithContext(() -> delegate.accept(eventData));
} else {
delegate.accept(eventData);
}
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
SessionContextAwareEventListener that = (SessionContextAwareEventListener) o;
return delegate != null ? delegate.equals(that.delegate) : that.delegate == null;
}
@Override
public int hashCode() {
return delegate != null ? delegate.hashCode() : 0;
}
}
private static class RunnableWrapper implements Consumer {
private final Runnable runnable;
public RunnableWrapper(Runnable runnable) {
this.runnable = runnable;
}
@Override
public void accept(T eventData) {
runnable.run();
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
RunnableWrapper that = (RunnableWrapper) o;
return runnable.equals(that.runnable);
}
@Override
public int hashCode() {
return Objects.hash(runnable);
}
}
}