/*
* 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 <tt>READ</tt> 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.
*/
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 <tt>select ... for update</tt>.
* @deprecated instead use PESSIMISTIC_WRITE
*/
public static final LockMode UPGRADE = new LockMode(10, "UPGRADE");
/**
* Attempt to obtain an upgrade lock, using an Oracle-style
* <tt>select for update nowait</tt>. The semantics of
* this lock mode, once obtained, are the same as
* <tt>UPGRADE</tt>.
*/
public static final LockMode UPGRADE_NOWAIT = new LockMode(10,
"UPGRADE_NOWAIT");
/**
* A <tt>WRITE</tt> 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()</tt> or <tt>lock()</tt> (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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