org.garret.jipc
Interface JIPCLock

All Superinterfaces:

JIPCPrimitive

public interface JIPCLock

extends JIPCPrimitive

Synchronization object for setting exlusive and shared locks. Locks are not nested - if session sets the same lock several time, all lock requests are succeed but single unlock request will unlock the object. It is possible to upgrade the lock: if session first lock object in shared mode and then in exclusive mode, lock will be upgraded to exclusive (Attention! upgrading locks can easily cause a deadlock if several session will try to upgrade their shared locks simultaneously).
It is not possible to downgrade the lock - locking of object in shared mode after granted exlusive lock has no effect.
Locks are granted in FIFO order - it means that if object is locked shared mode, then request for exclusive lock comes and is blocked and then if yet another request for shared lock is received, it will be also blocked and placed inqueue after excusive lock request. Server is able to detect deadlock for this primitive.

Semantic of methods inherited from JIPCPrimitive:

waitFor

set exlusive lock

reset

removes all locks (shared or exclusive). It is not required that session, invoking reset method be owner of this lock

Field Summary

Fields inherited from interface org.garret.jipc.JIPCPrimitive

DEFAULT_RANK

Method Summary

void	exclusiveLock() Set exlusive lock.
boolean	exclusiveLock(long timeout) Set exclusive lock with timeout.
void	priorityExclusiveLock(int rank) Set exlusive lock.
boolean	priorityExclusiveLock(int rank, long timeout) Set exclusive lock with timeout.
void	prioritySharedLock(int rank) Set shared lock.
boolean	prioritySharedLock(int rank, long timeout) Set shared lock with timeout.
void	sharedLock() Set shared lock.
boolean	sharedLock(long timeout) Set shared lock with timeout.
void	unlock() Remove lock from the object

Methods inherited from interface org.garret.jipc.JIPCPrimitive

alreadyExists, close, getName, priorityWait, priorityWait, reset, waitFor, waitFor

Method Detail

exclusiveLock

public void exclusiveLock()
                   throws JIPCException,
                          java.io.IOException

Set exlusive lock. No other session can set exclusive or shared lock.

JIPCException

java.io.IOException

exclusiveLock

public boolean exclusiveLock(long timeout)
                      throws JIPCException,
                             java.io.IOException

Set exclusive lock with timeout. If lock can not be graned within specifed time, request is failed.

Parameters:

timeout - time in milliseconds

Returns:

true if lock is granted, false of timeout is expired

JIPCException

java.io.IOException

priorityExclusiveLock

public void priorityExclusiveLock(int rank)
                           throws JIPCException,
                                  java.io.IOException

Set exlusive lock. No other session can set exclusive or shared lock.

Parameters:

rank - processes will be placed in wait queue in the order of increasing rank value and in the same order will be taken from the queue.

JIPCException

java.io.IOException

priorityExclusiveLock

public boolean priorityExclusiveLock(int rank,
                                     long timeout)
                              throws JIPCException,
                                     java.io.IOException

Set exclusive lock with timeout. If lock can not be graned within specifed time, request is failed.

Parameters:

rank - processes will be placed in wait queue in the order of increasing rank value and in the same order will be taken from the queue.

timeout - time in milliseconds

Returns:

true if lock is granted, false of timeout is expired

JIPCException

java.io.IOException

prioritySharedLock

public void prioritySharedLock(int rank)
                        throws JIPCException,
                               java.io.IOException

Set shared lock. No other session can set exclusive lock but other shared locks are possible.

Parameters:

rank - processes will be placed in wait queue in the order of increasing rank value and in the same order will be taken from the queue.

JIPCException

java.io.IOException

prioritySharedLock

public boolean prioritySharedLock(int rank,
                                  long timeout)
                           throws JIPCException,
                                  java.io.IOException

Set shared lock with timeout. If lock can not be graned within specifed time, request is failed.

Parameters:

rank - processes will be placed in wait queue in the order of increasing rank value and in the same order will be taken from the queue.

timeout - time in milliseconds

Returns:

true if lock is granted, false of timeout is expired

JIPCException

java.io.IOException

sharedLock

public void sharedLock()
                throws JIPCException,
                       java.io.IOException

Set shared lock. No other session can set exclusive lock but other shared locks are possible.

JIPCException

java.io.IOException

sharedLock

public boolean sharedLock(long timeout)
                   throws JIPCException,
                          java.io.IOException

Set shared lock with timeout. If lock can not be graned within specifed time, request is failed.

Parameters:

timeout - time in milliseconds

Returns:

true if lock is granted, false of timeout is expired

JIPCException

java.io.IOException

unlock

public void unlock()
            throws JIPCException,
                   java.io.IOException

Remove lock from the object

JIPCException

java.io.IOException