Package org.hibernate

Enum 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.

    A partial order of lock modes is defined such that every optimistic lock mode is considered a weaker sort of lock than evey pessimistic lock mode. If a session already holds a stronger lock level on a given entity when a weaker lock level is requested, then the request for the weaker lock level has no effect.

    Note that, in particular, a request for the optimistic lock level OPTIMISTIC_FORCE_INCREMENT on an entity for which any pessimistic lock is already held has no effect, and does not force a version increment.

    This enumeration of lock modes competes with the JPA-defined LockModeType, but offers additional options, including UPGRADE_NOWAIT and UPGRADE_SKIPLOCKED.

    See Also:
    Session.lock(Object, LockMode), LockModeType, LockOptions, OptimisticLocking

    • 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 turns out to be necessary to actually read the state from the database, rather than pull it from a cache.

        This is the "default" lock mode, the mode requested by calling Session.get(Class, Object) without passing an explicit mode. It permits the state of an object to be retrieved from the cache without the cost of database access.

        See Also:
        LockModeType.NONE

      • 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.

        Note that, despite the similar names this lock mode is not the same as the JPA-defined mode LockModeType.READ.

      • OPTIMISTIC

        public static final LockMode OPTIMISTIC
        A shared optimistic lock. Assumes that the current transaction will not experience contention for the state of an entity. The version will be checked near the end of the transaction, to verify that this was indeed the case.

        Only legal for versioned entity types.

        Note that this lock mode is the same as the JPA-defined modes LockModeType.READ and LockModeType.OPTIMISTIC.

        See Also:
        LockModeType.OPTIMISTIC

      • OPTIMISTIC_FORCE_INCREMENT

        public static final LockMode OPTIMISTIC_FORCE_INCREMENT
        A kind of exclusive optimistic lock. Assumes that the current transaction will not experience contention for the state of an entity. The version will be checked and incremented near the end of the transaction, to verify that this was indeed the case, and to signal to concurrent optimistic readers that their optimistic locks have failed.

        Only legal for versioned entity types.

        See Also:
        LockModeType.OPTIMISTIC_FORCE_INCREMENT

      • UPGRADE_NOWAIT

        public static final LockMode UPGRADE_NOWAIT
        A pessimistic upgrade lock, obtained using an Oracle-style select for update nowait. The semantics of this lock mode, if the lock is successfully obtained, are the same as PESSIMISTIC_WRITE. If the lock is not immediately available, an exception occurs.

      • UPGRADE_SKIPLOCKED

        public static final LockMode UPGRADE_SKIPLOCKED
        A pessimistic upgrade lock, obtained using an Oracle-style select for update skip locked. The semantics of this lock mode, if the lock is successfully obtained, are the same as PESSIMISTIC_WRITE. But if the lock is not immediately available, no exception occurs, but the locked row is not returned from the database.

      • PESSIMISTIC_READ

        public static final LockMode PESSIMISTIC_READ
        A pessimistic shared lock, which prevents concurrent transactions from writing the locked object. Obtained via a select for share statement in dialects where this syntax is supported, and via select for update in other dialects.

        On databases which do not support for share, this lock mode is equivalent to PESSIMISTIC_WRITE.

        See Also:
        LockModeType.PESSIMISTIC_READ

      • PESSIMISTIC_WRITE

        public static final LockMode PESSIMISTIC_WRITE
        A pessimistic upgrade lock, which prevents concurrent transactions from reading or writing the locked object. Obtained via a select for update statement.
        See Also:
        LockModeType.PESSIMISTIC_WRITE

      • PESSIMISTIC_FORCE_INCREMENT

        public static final LockMode PESSIMISTIC_FORCE_INCREMENT
        A pessimistic write lock which immediately increments the version of the locked object. Obtained by immediate execution of an update statement.

        Only legal for versioned entity types.

        See Also:
        LockModeType.PESSIMISTIC_FORCE_INCREMENT

    • 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

      • fromJpaLockMode

        public static LockMode fromJpaLockMode​(LockModeType lockMode)
        Returns:
        an instance with the same semantics as the given JPA LockModeType.

      • toJpaLockMode

        public static LockModeType toJpaLockMode​(LockMode lockMode)
        Returns:
        an instance of the JPA-defined LockModeType with similar semantics to the given LockMode.

      • toJpaLockMode

        public LockModeType toJpaLockMode()
        Returns:
        an instance of the JPA-defined LockModeType with similar semantics to this LockMode.

      • 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

      • requiresVersion

        public boolean requiresVersion()
        Does this lock mode require a version?
        Returns:
        true if this lock mode only applies to versioned entities

      • toExternalForm

        public String toExternalForm()

      • fromExternalForm

        public static LockMode fromExternalForm​(String externalForm)

      • toLockOptions

        public LockOptions toLockOptions()
        Returns:
        an instance of LockOptions with this lock mode, and all other settings defaulted.