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/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, Red Hat Middleware LLC 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 Middleware LLC.
 *
 * 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;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

/**
 * Instances represent a lock mode for a row of a relational
 * database table. It is not intended that users spend much
 * time worrying about locking since Hibernate usually
 * obtains exactly the right lock level automatically.
 * Some "advanced" users may wish to explicitly specify lock
 * levels.
 *
 * @see Session#lock(Object,LockMode)
 * @author Gavin King
 */
public final class LockMode implements Serializable {
	private final int level;
	private final String name;
	private static final Map INSTANCES = new HashMap();

	private LockMode(int level, String name) {
		this.level=level;
		this.name=name;
	}
	public String toString() {
		return name;
	}
	/**
	 * Check if this lock mode is more restrictive than the given lock mode.
	 *
	 * @param mode LockMode to check
	 * @return true if this lock mode is more restrictive than given lock mode
	 */
	public boolean greaterThan(LockMode mode) {
		return level > mode.level;
	}
	/**
	 * Check if this lock mode is less restrictive than the given lock mode.
	 *
	 * @param mode LockMode to check
	 * @return true if this lock mode is less restrictive than given lock mode
	 */
	public boolean lessThan(LockMode mode) {
		return level < mode.level;
	}
	/**
	 * No lock required. If an object is requested with this lock
	 * mode, a READ lock will be obtained if it is
	 * necessary to actually read the state from the database,
	 * rather than pull it from a cache.
*
* This is the "default" lock mode. */ public static final LockMode NONE = new LockMode(0, "NONE"); /** * A shared lock. Objects in this lock mode were read from * the database in the current transaction, rather than being * pulled from a cache. */ public static final LockMode READ = new LockMode(5, "READ"); /** * An upgrade lock. Objects loaded in this lock mode are * materialized using an SQL select ... for update. * @deprecated instead use PESSIMISTIC_WRITE */ public static final LockMode UPGRADE = new LockMode(10, "UPGRADE"); /** * Attempt to obtain an upgrade lock, using an Oracle-style * select for update nowait. The semantics of * this lock mode, once obtained, are the same as * UPGRADE. */ public static final LockMode UPGRADE_NOWAIT = new LockMode(10, "UPGRADE_NOWAIT"); /** * A WRITE lock is obtained when an object is updated * or inserted. This lock mode is for internal use only and is * not a valid mode for load() or lock() (both * of which throw exceptions if WRITE is specified). */ public static final LockMode WRITE = new LockMode(10, "WRITE"); /** * Similiar to {@link #UPGRADE} except that, for versioned entities, * it results in a forced version increment. * @deprecated instead use PESSIMISTIC_FORCE_INCREMENT */ public static final LockMode FORCE = new LockMode( 15, "FORCE" ); /** * start of javax.persistence.LockModeType equivalent modes */ /** * Optimisticly assume that transaction will not experience contention for * entities. The entity version will be verified near the transaction end. */ public static final LockMode OPTIMISTIC = new LockMode( 3, "OPTIMISTIC"); /** * Optimisticly assume that transaction will not experience contention for entities. * The entity version will be verified and incremented near the transaction end. */ public static final LockMode OPTIMISTIC_FORCE_INCREMENT = new LockMode( 4, "OPTIMISTIC_FORCE_INCREMENT"); /** * Implemented as PESSIMISTIC_WRITE. * TODO: introduce separate support for PESSIMISTIC_READ */ public static final LockMode PESSIMISTIC_READ = new LockMode( 12, "PESSIMISTIC_READ"); /** * Transaction will obtain a database lock immediately. * TODO: add PESSIMISTIC_WRITE_NOWAIT */ public static final LockMode PESSIMISTIC_WRITE = new LockMode( 13, "PESSIMISTIC_WRITE"); /** * Transaction will immediately increment the entity version. */ public static final LockMode PESSIMISTIC_FORCE_INCREMENT = new LockMode( 17, "PESSIMISTIC_FORCE_INCREMENT"); /** * end of javax.persistence.LockModeType modes */ static { INSTANCES.put( NONE.name, NONE ); INSTANCES.put( READ.name, READ ); INSTANCES.put( UPGRADE.name, UPGRADE ); INSTANCES.put( UPGRADE_NOWAIT.name, UPGRADE_NOWAIT ); INSTANCES.put( WRITE.name, WRITE ); INSTANCES.put( FORCE.name, FORCE ); INSTANCES.put( OPTIMISTIC.name, OPTIMISTIC); INSTANCES.put( OPTIMISTIC_FORCE_INCREMENT.name, OPTIMISTIC_FORCE_INCREMENT); INSTANCES.put( PESSIMISTIC_READ. name, PESSIMISTIC_READ); INSTANCES.put( PESSIMISTIC_WRITE.name, PESSIMISTIC_WRITE); INSTANCES.put( PESSIMISTIC_FORCE_INCREMENT.name, PESSIMISTIC_FORCE_INCREMENT); } private Object readResolve() { return parse( name ); } public static LockMode parse(String name) { return ( LockMode ) INSTANCES.get(name); } }




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