org.drools.core.event.AbstractEventSupport Maven / Gradle / Ivy
/*
* Copyright 2010 Red Hat, Inc. and/or its affiliates.
*
* 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.drools.core.event;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.util.Collections;
import java.util.EventListener;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.Consumer;
import org.kie.internal.runtime.Closeable;
/**
* Base class for Thread-safe Event Support in Drools. Note that subclasses wishing to access
* the listeners should do so via the getEventListenersIterator method. This
* will provide an Iterator accessing the current snapshot of the underlying list, freeing the
* subclasss of thread problems.
*
* Please note that for lists of small sizes, and few modifications, the CopyOnWriteArrayList
* provides best performance. If the list is modified more often, than a simple ArrayList
* with synchonized operations, and copying of the array for iteration is faster.
*/
public abstract class AbstractEventSupport implements Externalizable {
private static final long serialVersionUID = 510l;
private List listeners = new CopyOnWriteArrayList();
@SuppressWarnings("unchecked")
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
listeners = (List) in.readObject();
}
public void writeExternal(ObjectOutput out) throws IOException {
out.writeObject(listeners);
}
public void notifyAllListeners(Consumer consumer) {
if (!listeners.isEmpty()) {
listeners.forEach( l -> consumer.accept( l ) );
}
}
protected final Iterator getEventListenersIterator() {
return listeners.iterator();
}
/**
* Adds the specified listener to the list of listeners. Note that this method needs to be
* synchonized because it performs two independent operations on the underlying list
*
* @param listener to add
*/
public final synchronized void addEventListener(final E listener) {
if (!this.listeners.contains(listener)) {
this.listeners.add(listener);
}
}
/**
* Removes all event listeners of the specified class. Note that this method needs to be
* synchonized because it performs two independent operations on the underlying list
*
* @param cls class of listener to remove
*/
public final synchronized void removeEventListener(final Class cls) {
for (int listenerIndex = 0; listenerIndex < this.listeners.size();) {
E listener = this.listeners.get(listenerIndex);
if (cls.isAssignableFrom(listener.getClass())) {
this.listeners.remove(listenerIndex);
} else {
listenerIndex++;
}
}
}
public final void removeEventListener(final E listener) {
this.listeners.remove(listener);
}
public List getEventListeners() {
return Collections.unmodifiableList(this.listeners);
}
public final int size() {
return this.listeners.size();
}
public boolean isEmpty() {
return this.listeners.isEmpty();
}
public void clear() {
if (listeners != null) {
for (EventListener listener : listeners) {
if (listener instanceof Closeable) {
((Closeable) listener).close();
}
}
}
this.listeners.clear();
}
}