de.adorsys.lockpersistence.service

Interface LockService

All Known Implementing Classes:

LockServiceTemplate

public interface LockService

Strategy interface for server side implementations of a global lock. Implementations could be hopefully made for any back end that supports locks with these semantics. A lock is identified by name which is globally unique, i.e. there can be only one holder of the lock at a given time. Locks expire (in a way to be determined by the implementation), and have a String value (usually random) which is used by the lock holder to prove that he holds the lock. The value is thus unique per lock and per expiry period (i.e. 2 locks held at different times with the same name will have different values)..

Method Summary

Modifier and Type	Method and Description
Lock	create(String name) Acquire a lock by name.
Iterable<Lock>	findAll() Iterate the existing locks.
Lock	refresh(String name, String value) The holder of a lock can refresh it, extending its expiry.
void	release(String name, String value) Release a lock before it expires.

Method Detail

findAll

Iterable<Lock> findAll()

Iterate the existing locks.

Returns:

an iterable of all locks

create

Lock create(String name)
     throws LockExistsException

Acquire a lock by name. Only one process (globally) should be able to obtain and hold the lock with this name at any given time. Locks expire and can also be released by the owner, so after either of those events the lock can be acquired by the same or a different process.

Parameters:

name - the name identifying the lock

Returns:

a Lock containing a value that can be used to release or refresh the lock

Throws:

LockExistsException

release

void release(String name,
             String value)
      throws LockNotHeldException

Release a lock before it expires. Only the holder of a lock can release it, and the holder must have the correct unique value to prove that he holds it.

Parameters:

name - the name of the lock

value - the value of the lock (which has to match the value when it was acquired)

Throws:

LockNotHeldException

refresh

Lock refresh(String name,
             String value)
      throws LockNotHeldException

The holder of a lock can refresh it, extending its expiry. If the caller does not hold the lock there will be an exception, but the implementation may not be able to tell if it was because he formerly held the lock and it expired, or if it simply was never held.

Parameters:

name - the name of the lock

value - the value of the lock (which has to match the value when it was acquired)

Returns:

a new lock with a new value and a new expiry

Throws:

LockNotHeldException - if the value does not match the current value or if the lock doesn't exist (e.g. if it expired)