Hibernate example source code file (EventListenerGroupImpl.java)

This example Hibernate source code file (EventListenerGroupImpl.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Hibernate tags/keywords

arraylist, duplicate, duplicationstrategy, duplicationstrategy, eventlistenergroupimpl, eventlistenerregistrationexception, eventlistenerregistrationexception, eventtype, object, override, override, set, t, t, util

The Hibernate EventListenerGroupImpl.java source code

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2011, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.event.service.internal;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.ListIterator;
import java.util.Set;

import org.hibernate.event.spi.EventType;
import org.hibernate.event.service.spi.DuplicationStrategy;
import org.hibernate.event.service.spi.EventListenerGroup;
import org.hibernate.event.service.spi.EventListenerRegistrationException;

/**
 * @author Steve Ebersole
 */
public class EventListenerGroupImpl<T> implements EventListenerGroup {
	private EventType<T> eventType;

	private final Set<DuplicationStrategy> duplicationStrategies = new LinkedHashSet();
	private List<T> listeners;

	public EventListenerGroupImpl(EventType<T> eventType) {
		this.eventType = eventType;
		duplicationStrategies.add(
				// At minimum make sure we do not register the same exact listener class multiple times.
				new DuplicationStrategy() {
					@Override
					public boolean areMatch(Object listener, Object original) {
						return listener.getClass().equals( original.getClass() );
					}

					@Override
					public Action getAction() {
						return Action.ERROR;
					}
				}
		);
	}

	@Override
	public EventType<T> getEventType() {
		return eventType;
	}

	@Override
	public boolean isEmpty() {
		return count() <= 0;
	}

	@Override
	public int count() {
		return listeners == null ? 0 : listeners.size();
	}

	@Override
	public void clear() {
		if ( duplicationStrategies != null ) {
			duplicationStrategies.clear();
		}
		if ( listeners != null ) {
			listeners.clear();
		}
	}

	@Override
	public void addDuplicationStrategy(DuplicationStrategy strategy) {
		duplicationStrategies.add( strategy );
	}

	public Iterable<T> listeners() {
		return listeners == null ? Collections.<T>emptyList() : listeners;
	}

	@Override
	public void appendListeners(T... listeners) {
		for ( T listener : listeners ) {
			appendListener( listener );
		}
	}

	@Override
	public void appendListener(T listener) {
		if ( listenerShouldGetAdded( listener ) ) {
			internalAppend( listener );
		}
	}

	@Override
	public void prependListeners(T... listeners) {
		for ( T listener : listeners ) {
			prependListener( listener );
		}
	}

	@Override
	public void prependListener(T listener) {
		if ( listenerShouldGetAdded( listener ) ) {
			internalPrepend( listener );
		}
	}

	private boolean listenerShouldGetAdded(T listener) {
		if ( listeners == null ) {
			listeners = new ArrayList<T>();
			return true;
			// no need to do de-dup checks
		}

		boolean doAdd = true;
		strategy_loop: for ( DuplicationStrategy strategy : duplicationStrategies ) {
			final ListIterator<T> itr = listeners.listIterator();
			while ( itr.hasNext() ) {
				final T existingListener = itr.next();
				if ( strategy.areMatch( listener,  existingListener ) ) {
					switch ( strategy.getAction() ) {
						// todo : add debug logging of what happens here...
						case ERROR: {
							throw new EventListenerRegistrationException( "Duplicate event listener found" );
						}
						case KEEP_ORIGINAL: {
							doAdd = false;
							break strategy_loop;
						}
						case REPLACE_ORIGINAL: {
							itr.set( listener );
							doAdd = false;
							break strategy_loop;
						}
					}
				}
			}
		}
		return doAdd;
	}

	private void internalPrepend(T listener) {
		checkAgainstBaseInterface( listener );
		listeners.add( 0, listener );
	}

	private void checkAgainstBaseInterface(T listener) {
		if ( !eventType.baseListenerInterface().isInstance( listener ) ) {
			throw new EventListenerRegistrationException(
					"Listener did not implement expected interface [" + eventType.baseListenerInterface().getName() + "]"
			);
		}
	}

	private void internalAppend(T listener) {
		checkAgainstBaseInterface( listener );
		listeners.add( listener );
	}
}