org.hibernate

Enum LockMode

java.lang.Object

java.lang.Enum<LockMode>

org.hibernate.LockMode

All Implemented Interfaces:

Serializable, Comparable<LockMode>

public enum LockMode
extends Enum<LockMode>

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 Also:

Session.lock(Object, LockMode)

Enum Constant Summary

Enum Constants

Enum Constant and Description
FORCE Deprecated. instead use PESSIMISTIC_FORCE_INCREMENT
NONE No lock required.
OPTIMISTIC Optimisticly assume that transaction will not experience contention for entities.
OPTIMISTIC_FORCE_INCREMENT Optimisticly assume that transaction will not experience contention for entities.
PESSIMISTIC_FORCE_INCREMENT Transaction will immediately increment the entity version.
PESSIMISTIC_READ Implemented as PESSIMISTIC_WRITE.
PESSIMISTIC_WRITE Transaction will obtain a database lock immediately.
READ A shared lock.
UPGRADE Deprecated. instead use PESSIMISTIC_WRITE
UPGRADE_NOWAIT Attempt to obtain an upgrade lock, using an Oracle-style select for update nowait.
WRITE A WRITE lock is obtained when an object is updated or inserted.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	greaterThan(LockMode mode) Check if this lock mode is more restrictive than the given lock mode.
boolean	lessThan(LockMode mode) Check if this lock mode is less restrictive than the given lock mode.
static LockMode	valueOf(String name) Returns the enum constant of this type with the specified name.
static LockMode[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

NONE

public static final LockMode NONE

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.

READ

public static final LockMode READ

A shared lock. Objects in this lock mode were read from the database in the current transaction, rather than being pulled from a cache.

UPGRADE

@Deprecated
public static final LockMode UPGRADE

Deprecated. instead use PESSIMISTIC_WRITE

An upgrade lock. Objects loaded in this lock mode are materialized using an SQL select ... for update.

UPGRADE_NOWAIT

public static final LockMode UPGRADE_NOWAIT

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.

WRITE

public static final LockMode WRITE

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).

FORCE

@Deprecated
public static final LockMode FORCE

Deprecated. instead use PESSIMISTIC_FORCE_INCREMENT

Similiar to UPGRADE except that, for versioned entities, it results in a forced version increment.

OPTIMISTIC

public static final LockMode OPTIMISTIC

Optimisticly assume that transaction will not experience contention for entities. The entity version will be verified near the transaction end.

OPTIMISTIC_FORCE_INCREMENT

public static final LockMode OPTIMISTIC_FORCE_INCREMENT

Optimisticly assume that transaction will not experience contention for entities. The entity version will be verified and incremented near the transaction end.

PESSIMISTIC_READ

public static final LockMode PESSIMISTIC_READ

Implemented as PESSIMISTIC_WRITE. TODO: introduce separate support for PESSIMISTIC_READ

PESSIMISTIC_WRITE

public static final LockMode PESSIMISTIC_WRITE

Transaction will obtain a database lock immediately. TODO: add PESSIMISTIC_WRITE_NOWAIT

PESSIMISTIC_FORCE_INCREMENT

public static final LockMode PESSIMISTIC_FORCE_INCREMENT

Transaction will immediately increment the entity version.

Method Detail

values

public static LockMode[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (LockMode c : LockMode.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static LockMode valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

greaterThan

public boolean greaterThan(LockMode mode)

Check if this lock mode is more restrictive than the given lock mode.

Parameters:

mode - LockMode to check

Returns:

true if this lock mode is more restrictive than given lock mode

lessThan

public boolean lessThan(LockMode mode)

Check if this lock mode is less restrictive than the given lock mode.

Parameters:

mode - LockMode to check

Returns:

true if this lock mode is less restrictive than given lock mode