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Hibernate's entity version (audit/history) support
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/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008-2011, 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.envers.reader;
import java.util.Map;

import org.jboss.logging.Logger;

import org.hibernate.envers.internal.EnversMessageLogger;
import org.hibernate.envers.tools.Triple;

import static org.hibernate.envers.tools.Tools.newHashMap;
import static org.hibernate.envers.tools.Triple.make;

/**
 * First level cache for versioned entities, versions reader-scoped. Each entity is uniquely identified by a
 * revision number and entity id.
 * @author Adam Warski (adam at warski dot org)
 * @author Hernán Chanfreau
 */
public class FirstLevelCache {

    public static final EnversMessageLogger LOG = Logger.getMessageLogger(EnversMessageLogger.class, FirstLevelCache.class.getName());

    /**
     * cache for resolve an object for a given id, revision and entityName.
     */
    private final Map, Object> cache;

    /**
     * used to resolve the entityName for a given id, revision and entity.
     */
    private final Map, String> entityNameCache;

    public FirstLevelCache() {
        cache = newHashMap();
        entityNameCache = newHashMap();
    }

    public Object get(String entityName, Number revision, Object id) {
        LOG.debugf("Resolving object from First Level Cache: EntityName:%s - primaryKey:%s - revision:%s", entityName, id, revision);
        return cache.get(make(entityName, revision, id));
    }

    public void put(String entityName, Number revision, Object id, Object entity) {
        LOG.debugf("Caching entity on First Level Cache:  - primaryKey:%s - revision:%s - entityName:%s", id, revision, entityName);
        cache.put(make(entityName, revision, id), entity);
    }

    public boolean contains(String entityName, Number revision, Object id) {
        return cache.containsKey(make(entityName, revision, id));
    }

    /**
     * Adds the entityName into the cache. The key is a triple make with primaryKey, revision and entity
     * @param id primaryKey
     * @param revision revision number
     * @param entity object retrieved by envers
     * @param entityName value of the cache
     */
    public void putOnEntityNameCache(Object id, Number revision, Object entity, String entityName) {
        LOG.debugf("Caching entityName on First Level Cache:  - primaryKey:%s - revision:%s - entity:%s -> entityName:%s",
                   id,
                   revision,
                   entity.getClass().getName(),
                   entityName);
    	entityNameCache.put(make(id, revision, entity), entityName);
    }

    /**
     * Gets the entityName from the cache. The key is a triple make with primaryKey, revision and entity
	 *
     * @param id primaryKey
     * @param revision revision number
     * @param entity object retrieved by envers
	 *
	 * @return The appropriate entity name
     */
    public String getFromEntityNameCache(Object id, Number revision, Object entity) {
        LOG.debugf("Trying to resolve entityName from First Level Cache: - primaryKey:%s - revision:%s - entity:%s",
                   id,
                   revision,
                   entity);
    	return entityNameCache.get(make(id, revision, entity));
    }

	/**
	 * @param id primaryKey
	 * @param revision revision number
	 * @param entity object retrieved by envers
	 * @return true if entityNameCache contains the triple
	 */
    public boolean containsEntityName(Object id, Number revision, Object entity) {
    	return entityNameCache.containsKey(make(id, revision, entity));
    }
}