Hibernate example source code file (LockMode.java)

This example Hibernate source code file (LockMode.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

force, lockmode, lockmode, none, none, optimistic, optimistic_force_increment, pessimistic_force_increment, pessimistic_force_increment, pessimistic_write, pessimistic_write, upgrade, upgrade_nowait, write

The Hibernate LockMode.java source code

/*
 * 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;

/**
 * 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.
 *
 * @author Gavin King
 * @see Session#lock(Object, LockMode)
 */
public enum LockMode {
	/**
	 * No lock required. If an object is requested with this lock
	 * mode, a <tt>READ lock will be obtained if it is
	 * necessary to actually read the state from the database,
	 * rather than pull it from a cache.<br>
	 * <br>
	 * This is the "default" lock mode.
	 */
	NONE( 0 ),
	/**
	 * A shared lock. Objects in this lock mode were read from
	 * the database in the current transaction, rather than being
	 * pulled from a cache.
	 */
	READ( 5 ),
	/**
	 * An upgrade lock. Objects loaded in this lock mode are
	 * materialized using an SQL <tt>select ... for update.
	 *
	 * @deprecated instead use PESSIMISTIC_WRITE
	 */
	UPGRADE( 10 ),
	/**
	 * Attempt to obtain an upgrade lock, using an Oracle-style
	 * <tt>select for update nowait. The semantics of
	 * this lock mode, once obtained, are the same as
	 * <tt>UPGRADE.
	 */
	UPGRADE_NOWAIT( 10 ),
	/**
	 * A <tt>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 <tt>load() or lock() (both
	 * of which throw exceptions if WRITE is specified).
	 */
	WRITE( 10 ),

	/**
	 * Similiar to {@link #UPGRADE} except that, for versioned entities,
	 * it results in a forced version increment.
	 *
	 * @deprecated instead use PESSIMISTIC_FORCE_INCREMENT
	 */
	FORCE( 15 ),

	/**
	 *  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.
	 */
	OPTIMISTIC( 3 ),

	/**
	 * Optimisticly assume that transaction will not experience contention for entities.
	 * The entity version will be verified and incremented near the transaction end.
	 */
	OPTIMISTIC_FORCE_INCREMENT( 4 ),

	/**
	 * Implemented as PESSIMISTIC_WRITE.
	 * TODO:  introduce separate support for PESSIMISTIC_READ
	 */
	PESSIMISTIC_READ( 12 ),

	/**
	 * Transaction will obtain a database lock immediately.
	 * TODO:  add PESSIMISTIC_WRITE_NOWAIT
	 */
	PESSIMISTIC_WRITE( 13 ),

	/**
	 * Transaction will immediately increment the entity version.
	 */
	PESSIMISTIC_FORCE_INCREMENT( 17 );
	private final int level;

	private LockMode(int level) {
		this.level = level;
	}

	/**
	 * 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;
	}


}