org.exolab.jms.scheduler
Class Scheduler

java.lang.Object
  |
  +--org.exolab.core.service.Service
        |
        +--org.exolab.core.service.BasicService
              |
              +--org.exolab.jms.scheduler.Scheduler

All Implemented Interfaces:

java.lang.Runnable, java.io.Serializable, org.exolab.core.service.Serviceable

public class Scheduler

extends org.exolab.core.service.BasicService

The scheduler is responsible for executing Runnable objects using a thread pool. Clients can add these objects to the scheduler and the scheduler will, in fifo order, execute them. If there are no threads currently available, the runnable will wait for one to become available.

A client can add or remove Runnable objects.

Version:

$Revision: 1.9 $ $Date: 2003/08/17 01:32:25 $

Author:

Jim Mourikis, Tim Anderson, Jim Alateras

See Also:

Runnable, BasicService, ThreadPool, Serialized Form

Method Summary

void	add(java.lang.Runnable runner) Add a Runnable object to the scheduler queue.
boolean	contains(java.lang.Runnable runner) Returns if a Runnable object exists in the scheduler queue.
static Scheduler	createInstance() Creates the singleton instance
static Scheduler	instance() Returns the singleton instance
boolean	isEmpty() Returns true if the scheduler queue is empty
protected java.lang.Runnable	next() Return the next object in the queue to execute This method blocks until an object becomes available.
boolean	remove(java.lang.Runnable runner) Remove a Runnable object from the scheduler queue.
void	run() Start the scheduler This can only be terminated by invoking stop()
void	stop()

Methods inherited from class org.exolab.core.service.BasicService

start, toString

Methods inherited from class org.exolab.core.service.Service

getName, getState, restart, setState

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

createInstance

public static Scheduler createInstance()
                                throws org.exolab.core.service.ServiceException

Creates the singleton instance

Throws:

org.exolab.core.service.ServiceException - if the scheduler can't be created

instance

public static Scheduler instance()

Returns the singleton instance

Returns:

the singleton instance, or null if it hasn't been initialised

add

public void add(java.lang.Runnable runner)

Add a Runnable object to the scheduler queue. When a thread becomes available, it will be executed.

Parameters:

runner - the object to execute

remove

public boolean remove(java.lang.Runnable runner)

Remove a Runnable object from the scheduler queue.

Parameters:

runner - the object to remove

Returns:

boolean true if the object was removed, false if it is already running or doesn't exist

contains

public boolean contains(java.lang.Runnable runner)

Returns if a Runnable object exists in the scheduler queue.

Parameters:

runner - the object to remove

Returns:

boolean true if the object exists, false if it is already running or doesn't exist

isEmpty

public boolean isEmpty()

Returns true if the scheduler queue is empty

Returns:

true if the scheduler queue is empty

run

public void run()

Start the scheduler This can only be terminated by invoking stop()

Overrides:

run in class org.exolab.core.service.BasicService

stop

public void stop()
          throws org.exolab.core.service.ServiceException

Overrides:

stop in class org.exolab.core.service.BasicService

next

protected java.lang.Runnable next()

Return the next object in the queue to execute This method blocks until an object becomes available.

Returns:

Runnable the next object to execute