Module jakarta.persistence

Package jakarta.persistence

Enum Class LockModeType

java.lang.Object

java.lang.Enum<LockModeType>

jakarta.persistence.LockModeType

All Implemented Interfaces:

FindOption, RefreshOption, Serializable, Comparable<LockModeType>, Constable

public enum LockModeType
extends Enum<LockModeType>
implements FindOption, RefreshOption

Enumerates the kinds of optimistic or pessimistic lock which may be obtained on an entity instance.

A specific lock mode may be requested by passing an explicit LockModeType as an argument to:

• one of the methods of EntityManager which obtains locks (lock(), find(), or refresh()), or
• to Query.setLockMode(LockModeType) or TypedQuery.setLockMode(LockModeType).

Lock modes other than NONE prevent dirty reads and non-repeatable reads of locked entity data within the current transaction.

An optimistic lock is requested by specifying the lock mode type OPTIMISTIC or OPTIMISTIC_FORCE_INCREMENT. The lock mode types READ and WRITE are synonyms for OPTIMISTIC and OPTIMISTIC_FORCE_INCREMENT respectively. The latter are preferred for new applications.

The persistence implementation is not required to accept requests for optimistic locks on non-versioned entities. When a provider does not support such a lock request, it must throw PersistenceException.

An immediate pessimistic database-level lock is requested by specifying one of the lock mode types PESSIMISTIC_READ, PESSIMISTIC_WRITE, or PESSIMISTIC_FORCE_INCREMENT.

• A lock with type PESSIMISTIC_WRITE can be obtained on an entity instance to force serialization among transactions attempting to update the entity data.
• A lock with type PESSIMISTIC_READ can be used to query data using repeatable-read semantics without the need to reread the data at the end of the transaction to obtain a lock, and without blocking other transactions reading the data.
• A lock with type PESSIMISTIC_WRITE can be used when querying data and there is a high likelihood of deadlock or update failure among concurrent updating transactions.

The persistence implementation must accept requests for locks of type PESSIMISTIC_READ and PESSIMISTIC_WRITE on both versioned and non-versioned entities.

• When the lock cannot be obtained, and the database locking failure results in transaction-level rollback, the provider must throw PessimisticLockException and ensure that the JTA transaction or EntityTransaction has been marked for rollback.
• When the lock cannot be obtained, and the database locking failure results in only statement-level rollback, the provider must throw the LockTimeoutException (and must not mark the transaction for rollback).

The persistence implementation is not required to accept requests for locks of type PESSIMISTIC_FORCE_INCREMENT on non-versioned entities. When a provider does not support such a lock request, it must throw PersistenceException.

Since:

1.0

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Enum

Enum.EnumDesc<E extends Enum<E>>

Enum Constant Summary

Enum Constants

Enum Constant	Description
NONE	No lock.
OPTIMISTIC	An optimistic lock.
OPTIMISTIC_FORCE_INCREMENT	Optimistic lock, with version update, which prevents the following phenomena:
PESSIMISTIC_FORCE_INCREMENT	Pessimistic write lock, with version update.
PESSIMISTIC_READ	Pessimistic read lock.
PESSIMISTIC_WRITE	Pessimistic write lock.
READ	Synonymous with OPTIMISTIC.
WRITE	Synonymous with OPTIMISTIC_FORCE_INCREMENT.

Method Summary

Modifier and Type	Method	Description
static LockModeType	valueOf(String name)	Returns the enum constant of this class with the specified name.
static LockModeType[]	values()	Returns an array containing the constants of this enum class, in the order they are declared.

Methods inherited from class java.lang.Enum

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

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Details

READ

public static final LockModeType READ

Synonymous with OPTIMISTIC.

OPTIMISTIC is preferred for new applications.

WRITE

public static final LockModeType WRITE

Synonymous with OPTIMISTIC_FORCE_INCREMENT.

OPTIMISTIC_FORCE_INCREMENT is preferred for new applications.

OPTIMISTIC

public static final LockModeType OPTIMISTIC

An optimistic lock.

If transaction T1 calls for a lock of type OPTIMISTIC on a versioned object, the entity manager must ensure that neither of the following phenomena can occur:

• P1 Dirty read: Transaction T1 modifies a row. Another transaction T2 then reads that row and obtains the modified value, before T1 has committed or rolled back. Transaction T2 eventually commits successfully; it does not matter whether T1 commits or rolls back and whether it does so before or after T2 commits.
• P2 Non-repeatable read: Transaction T1 reads a row. Another transaction T2 then modifies or deletes that row, before T1 has committed. Both transactions eventually commit successfully.

The persistence implementation is not required to accept requests for OPTIMISTIC locks on non-versioned entities.

Since:

2.0

OPTIMISTIC_FORCE_INCREMENT

public static final LockModeType OPTIMISTIC_FORCE_INCREMENT

Optimistic lock, with version update, which prevents the following phenomena:

If transaction T1 calls for a lock of type OPTIMISTIC_FORCE_INCREMENT on a versioned object, the entity manager must ensure that neither of the following phenomena can occur:

• P1 Dirty read: Transaction T1 modifies a row. Another transaction T2 then reads that row and obtains the modified value, before T1 has committed or rolled back. Transaction T2 eventually commits successfully; it does not matter whether T1 commits or rolls back and whether it does so before or after T2 commits.
• P2 Non-repeatable read: Transaction T1 reads a row. Another transaction T2 then modifies or deletes that row, before T1 has committed. Both transactions eventually commit successfully.

In addition, obtaining a lock of type OPTIMISTIC_FORCE_INCREMENT on a versioned entity will also force an update (increment) to the version column.

The persistence implementation is not required to accept requests for OPTIMISTIC_FORCE_INCREMENT locks on non-versioned entities.

Since:

2.0

PESSIMISTIC_READ

public static final LockModeType PESSIMISTIC_READ

Pessimistic read lock.

If transaction T1 calls for a lock of type PESSIMISTIC_READ on an object, the entity manager must ensure that neither of the following phenomena can occur:

• P1 Dirty read: Transaction T1 modifies a row. Another transaction T2 then reads that row and obtains the modified value, before T1 has committed or rolled back.
• P2 Non-repeatable read: Transaction T1 reads a row. Another transaction T2 then modifies or deletes that row, before T1 has committed or rolled back.

Since:

2.0

PESSIMISTIC_WRITE

public static final LockModeType PESSIMISTIC_WRITE

Pessimistic write lock.

If transaction T1 calls for a lock of type PESSIMISTIC_WRITE on an object, the entity manager must ensure that neither of the following phenomena can occur:

• P1 Dirty read: Transaction T1 modifies a row. Another transaction T2 then reads that row and obtains the modified value, before T1 has committed or rolled back.
• P2 Non-repeatable read: Transaction T1 reads a row. Another transaction T2 then modifies or deletes that row, before T1 has committed or rolled back.

Since:

2.0

PESSIMISTIC_FORCE_INCREMENT

public static final LockModeType PESSIMISTIC_FORCE_INCREMENT

Pessimistic write lock, with version update.

If transaction T1 calls for a lock of type PESSIMISTIC_FORCE_INCREMENT on an object, the entity manager must ensure that neither of the following phenomena can occur:

• P1 Dirty read: Transaction T1 modifies a row. Another transaction T2 then reads that row and obtains the modified value, before T1 has committed or rolled back.
• P2 Non-repeatable read: Transaction T1 reads a row. Another transaction T2 then modifies or deletes that row, before T1 has committed or rolled back.

In addition, obtaining a lock of type PESSIMISTIC_FORCE_INCREMENT on a versioned entity will also force an update (increment) to the version column.

The persistence implementation is not required to accept requests for PESSIMISTIC_FORCE_INCREMENT locks on non-versioned entities.

Since:

2.0

NONE

public static final LockModeType NONE

No lock.

Since:

2.0

Method Details

values

public static LockModeType[] values()

Returns an array containing the constants of this enum class, in the order they are declared.

Returns:

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

valueOf

public static LockModeType valueOf(String name)

Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (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 class has no constant with the specified name

NullPointerException - if the argument is null