/*
* Copyright 2002-2010 the original author or authors.
*
* 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 org.springframework.context.event;
import java.util.Collection;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.core.OrderComparator;
/**
* Abstract implementation of the {@link ApplicationEventMulticaster} interface,
* providing the basic listener registration facility.
*
* <p>Doesn't permit multiple instances of the same listener by default,
* as it keeps listeners in a linked Set. The collection class used to hold
* ApplicationListener objects can be overridden through the "collectionClass"
* bean property.
*
* <p>Implementing ApplicationEventMulticaster's actual {@link #multicastEvent} method
* is left to subclasses. {@link SimpleApplicationEventMulticaster} simply multicasts
* all events to all registered listeners, invoking them in the calling thread.
* Alternative implementations could be more sophisticated in those respects.
*
* @author Juergen Hoeller
* @since 1.2.3
* @see #getApplicationListeners(ApplicationEvent)
* @see SimpleApplicationEventMulticaster
*/
public abstract class AbstractApplicationEventMulticaster implements ApplicationEventMulticaster, BeanFactoryAware {
private final ListenerRetriever defaultRetriever = new ListenerRetriever(false);
private final Map<ListenerCacheKey, ListenerRetriever> retrieverCache =
new ConcurrentHashMap<ListenerCacheKey, ListenerRetriever>();
private BeanFactory beanFactory;
public void addApplicationListener(ApplicationListener listener) {
synchronized (this.defaultRetriever) {
this.defaultRetriever.applicationListeners.add(listener);
this.retrieverCache.clear();
}
}
public void addApplicationListenerBean(String listenerBeanName) {
synchronized (this.defaultRetriever) {
this.defaultRetriever.applicationListenerBeans.add(listenerBeanName);
this.retrieverCache.clear();
}
}
public void removeApplicationListener(ApplicationListener listener) {
synchronized (this.defaultRetriever) {
this.defaultRetriever.applicationListeners.remove(listener);
this.retrieverCache.clear();
}
}
public void removeApplicationListenerBean(String listenerBeanName) {
synchronized (this.defaultRetriever) {
this.defaultRetriever.applicationListenerBeans.remove(listenerBeanName);
this.retrieverCache.clear();
}
}
public void removeAllListeners() {
synchronized (this.defaultRetriever) {
this.defaultRetriever.applicationListeners.clear();
this.defaultRetriever.applicationListenerBeans.clear();
this.retrieverCache.clear();
}
}
public final void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
private BeanFactory getBeanFactory() {
if (this.beanFactory == null) {
throw new IllegalStateException("ApplicationEventMulticaster cannot retrieve listener beans " +
"because it is not associated with a BeanFactory");
}
return this.beanFactory;
}
/**
* Return a Collection containing all ApplicationListeners.
* @return a Collection of ApplicationListeners
* @see org.springframework.context.ApplicationListener
*/
protected Collection<ApplicationListener> getApplicationListeners() {
return this.defaultRetriever.getApplicationListeners();
}
/**
* Return a Collection of ApplicationListeners matching the given
* event type. Non-matching listeners get excluded early.
* @param event the event to be propagated. Allows for excluding
* non-matching listeners early, based on cached matching information.
* @return a Collection of ApplicationListeners
* @see org.springframework.context.ApplicationListener
*/
protected Collection<ApplicationListener> getApplicationListeners(ApplicationEvent event) {
Class<? extends ApplicationEvent> eventType = event.getClass();
Class sourceType = event.getSource().getClass();
ListenerCacheKey cacheKey = new ListenerCacheKey(eventType, sourceType);
ListenerRetriever retriever = this.retrieverCache.get(cacheKey);
if (retriever != null) {
return retriever.getApplicationListeners();
}
else {
retriever = new ListenerRetriever(true);
LinkedList<ApplicationListener> allListeners = new LinkedList<ApplicationListener>();
synchronized (this.defaultRetriever) {
for (ApplicationListener listener : this.defaultRetriever.applicationListeners) {
if (supportsEvent(listener, eventType, sourceType)) {
retriever.applicationListeners.add(listener);
allListeners.add(listener);
}
}
if (!this.defaultRetriever.applicationListenerBeans.isEmpty()) {
BeanFactory beanFactory = getBeanFactory();
for (String listenerBeanName : this.defaultRetriever.applicationListenerBeans) {
ApplicationListener listener = beanFactory.getBean(listenerBeanName, ApplicationListener.class);
if (!allListeners.contains(listener) && supportsEvent(listener, eventType, sourceType)) {
retriever.applicationListenerBeans.add(listenerBeanName);
allListeners.add(listener);
}
}
}
OrderComparator.sort(allListeners);
this.retrieverCache.put(cacheKey, retriever);
}
return allListeners;
}
}
/**
* Determine whether the given listener supports the given event.
* <p>The default implementation detects the {@link SmartApplicationListener}
* interface. In case of a standard {@link ApplicationListener}, a
* {@link GenericApplicationListenerAdapter} will be used to introspect
* the generically declared type of the target listener.
* @param listener the target listener to check
* @param eventType the event type to check against
* @param sourceType the source type to check against
* @return whether the given listener should be included in the
* candidates for the given event type
*/
protected boolean supportsEvent(
ApplicationListener listener, Class<? extends ApplicationEvent> eventType, Class sourceType) {
SmartApplicationListener smartListener = (listener instanceof SmartApplicationListener ?
(SmartApplicationListener) listener : new GenericApplicationListenerAdapter(listener));
return (smartListener.supportsEventType(eventType) && smartListener.supportsSourceType(sourceType));
}
/**
* Cache key for ListenerRetrievers, based on event type and source type.
*/
private static class ListenerCacheKey {
private final Class eventType;
private final Class sourceType;
public ListenerCacheKey(Class eventType, Class sourceType) {
this.eventType = eventType;
this.sourceType = sourceType;
}
@Override
public boolean equals(Object other) {
if (this == other) {
return true;
}
ListenerCacheKey otherKey = (ListenerCacheKey) other;
return (this.eventType.equals(otherKey.eventType) && this.sourceType.equals(otherKey.sourceType));
}
@Override
public int hashCode() {
return this.eventType.hashCode() * 29 + this.sourceType.hashCode();
}
}
/**
* Helper class that encapsulates a specific set of target listeners,
* allowing for efficient retrieval of pre-filtered listeners.
* <p>An instance of this helper gets cached per event type and source type.
*/
private class ListenerRetriever {
public final Set<ApplicationListener> applicationListeners;
public final Set<String> applicationListenerBeans;
private final boolean preFiltered;
public ListenerRetriever(boolean preFiltered) {
this.applicationListeners = new LinkedHashSet<ApplicationListener>();
this.applicationListenerBeans = new LinkedHashSet<String>();
this.preFiltered = preFiltered;
}
public Collection<ApplicationListener> getApplicationListeners() {
LinkedList<ApplicationListener> allListeners = new LinkedList<ApplicationListener>();
for (ApplicationListener listener : this.applicationListeners) {
allListeners.add(listener);
}
if (!this.applicationListenerBeans.isEmpty()) {
BeanFactory beanFactory = getBeanFactory();
for (String listenerBeanName : this.applicationListenerBeans) {
ApplicationListener listener = beanFactory.getBean(listenerBeanName, ApplicationListener.class);
if (this.preFiltered || !allListeners.contains(listener)) {
allListeners.add(listener);
}
}
}
OrderComparator.sort(allListeners);
return allListeners;
}
}
}