/*
* Copyright 2002-2007 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 org.springframework.beans.BeanUtils;
import org.springframework.context.ApplicationListener;
import org.springframework.core.CollectionFactory;
/**
* 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 #setCollectionClass
* @see #getApplicationListeners()
* @see SimpleApplicationEventMulticaster
*/
public abstract class AbstractApplicationEventMulticaster implements ApplicationEventMulticaster {
/** Collection of ApplicationListeners */
private Collection applicationListeners = new LinkedHashSet();
/**
* Set whether this multicaster should expect concurrent updates at runtime
* (i.e. after context startup finished). In case of concurrent updates,
* a copy-on-write strategy is applied, keeping iteration (for multicasting)
* without synchronization while still making listener updates thread-safe.
*/
public void setConcurrentUpdates(boolean concurrent) {
Collection newColl = (concurrent ? CollectionFactory.createCopyOnWriteSet() : new LinkedHashSet());
// Add all previously registered listeners (usually none).
newColl.addAll(this.applicationListeners);
this.applicationListeners = newColl;
}
/**
* Specify the collection class to use. Can be populated with a fully
* qualified class name when defined in a Spring application context.
* <p>Default is a linked HashSet, keeping the registration order.
* Note that a Set class specified will not permit multiple instances
* of the same listener, while a List class will allow for registering
* the same listener multiple times.
*/
public void setCollectionClass(Class collectionClass) {
if (collectionClass == null) {
throw new IllegalArgumentException("'collectionClass' must not be null");
}
if (!Collection.class.isAssignableFrom(collectionClass)) {
throw new IllegalArgumentException("'collectionClass' must implement [java.util.Collection]");
}
// Create desired collection instance.
Collection newColl = (Collection) BeanUtils.instantiateClass(collectionClass);
// Add all previously registered listeners (usually none).
newColl.addAll(this.applicationListeners);
this.applicationListeners = newColl;
}
public void addApplicationListener(ApplicationListener listener) {
this.applicationListeners.add(listener);
}
public void removeApplicationListener(ApplicationListener listener) {
this.applicationListeners.remove(listener);
}
public void removeAllListeners() {
this.applicationListeners.clear();
}
/**
* Return the current Collection of ApplicationListeners.
* <p>Note that this is the raw Collection of ApplicationListeners,
* potentially modified when new listeners get registered or
* existing ones get removed. This Collection is not a snapshot copy.
* @return a Collection of ApplicationListeners
* @see org.springframework.context.ApplicationListener
*/
protected Collection getApplicationListeners() {
return this.applicationListeners;
}
}