javax.persistence
Enum LockModeType

java.lang.Object
  java.lang.Enum<LockModeType>
      javax.persistence.LockModeType

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<LockModeType>

public enum LockModeType
extends java.lang.Enum<LockModeType>

Six lock mode types are defined: OPTIMISTIC, OPTIMISTIC_FORCE_INCREMENT, PESSIMISTIC_READ, PESSIMISTIC_WRITE, PESSIMISTIC_FORCE_INCREMENT, NONE. The lock mode type values READ and WRITE are synonyms of OPTIMISTIC and OPTIMISTIC_FORCE_INCREMENT respectively. The latter are to be preferred for new applications.

Lock modes OPTIMISTIC and OPTIMISTIC_FORCE_INCREMENT are used for optimistic locking. The semantics of requesting locks of type LockModeType.OPTIMISTIC and LockMode- Type.OPTIMISTIC_FORCE_INCREMENT are the following.

If transaction T1 calls lock(entity, LockModeType.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.

Lock modes PESSIMISTIC_READ, PESSIMISTIC_WRITE, and PESSIMISTIC_FORCE_INCREMENT are used to immediately obtain long-term database locks. The semantics of requesting locks of type LockModeType.PESSIMISTIC_READ, LockMode- Type.PESSIMISTIC_WRITE, and LockModeType.PESSIMISTIC_FORCE_INCREMENT are the following.

If transaction T1 calls lock(entity, LockModeType.PESSIMISTIC_READ) or lock(entity, LockModeType.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.

Any such lock must be obtained immediately and retained until transaction T1 completes (commits or rolls back).

See Also:

EntityManager.find(Class, Object, LockModeType), EntityManager.find(Class, Object, LockModeType, java.util.Map), EntityManager.getLockMode(Object), EntityManager.lock(Object, LockModeType), EntityManager.lock(Object, LockModeType, java.util.Map), EntityManager.refresh(Object, LockModeType), EntityManager.refresh(Object, LockModeType, java.util.Map), NamedQuery.lockMode(), Query.getLockMode()

Since:

Java Persistence 2.0

Enum Constant Summary

NONE
No locking

OPTIMISTIC
Equivalent to READ lock

OPTIMISTIC_FORCE_INCREMENT
Equivalent to WRITE lock

PESSIMISTIC_FORCE_INCREMENT

PESSIMISTIC_READ

PESSIMISTIC_WRITE

READ
Read lock READ is synonymous with OPTIMISTIC.

WRITE
Write lock WRITE is synonymous with OPTIMISTIC_FORCE_INCREMENT.

Method Summary

static LockModeType	valueOf(java.lang.String name) Returns the enum constant of this type with the specified name.
static LockModeType[]	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

READ

public static final LockModeType READ

Read lock READ is synonymous with OPTIMISTIC.

WRITE

public static final LockModeType WRITE

Write lock WRITE is synonymous with OPTIMISTIC_FORCE_INCREMENT.

OPTIMISTIC

public static final LockModeType OPTIMISTIC

Equivalent to READ lock

Since:

Java Persistence 2.0

OPTIMISTIC_FORCE_INCREMENT

public static final LockModeType OPTIMISTIC_FORCE_INCREMENT

Equivalent to WRITE lock

Since:

Java Persistence 2.0

PESSIMISTIC_READ

public static final LockModeType PESSIMISTIC_READ

Since:

Java Persistence 2.0

PESSIMISTIC_WRITE

public static final LockModeType PESSIMISTIC_WRITE

Since:

Java Persistence 2.0

PESSIMISTIC_FORCE_INCREMENT

public static final LockModeType PESSIMISTIC_FORCE_INCREMENT

Since:

Java Persistence 2.0

NONE

public static final LockModeType NONE

No locking

Since:

Java Persistence 2.0

Method Detail

values

public static LockModeType[] 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 (LockModeType c : LockModeType.values())
    System.out.println(c);

Returns:

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

valueOf

public static LockModeType valueOf(java.lang.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:

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

java.lang.NullPointerException - if the argument is null