wt.jmx.core
Class PeriodicTaskSupport

java.lang.Object
  wt.jmx.core.PeriodicTaskSupport

public abstract class PeriodicTaskSupport
extends Object

This abstract class takes care of most of the drudgery of properly setting up a task for repeated execution on a specific, periodic interval. This includes support for start() and stop() lifecycle operations as well as changes to the interval frequency.

Note that though this class defaults to daemon threads unless otherwise specified by the caller. Also note that the default implementation of createExecutor() returns a SharedScheduledExecutor as the backing executor, which implies some limitations as compared to normal ScheduledExecutorService implementations.

Supported API: true

Extendable: true

Constructor Summary

PeriodicTaskSupport()
Default constructor

Supported API: true

PeriodicTaskSupport(boolean daemon)
Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport(boolean daemon, int taskIntervalSeconds)
Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport(int taskIntervalSeconds)
Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport(String timerThreadNamePrefix)
Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport(String timerThreadNamePrefix, boolean daemon)
Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport(String timerThreadNamePrefix, boolean daemon, int taskIntervalSeconds)
Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport(String timerThreadNamePrefix, boolean daemon, int taskIntervalSeconds, int firstExecutionDelaySeconds)
Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport(String timerThreadNamePrefix, boolean daemon, int taskIntervalSeconds, int firstExecutionDelaySeconds, boolean fixedDelay)
Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport(String timerThreadNamePrefix, int taskIntervalSeconds)
Constructor; arguments set corresponding properties

Supported API: true

Method Summary

protected ScheduledExecutorService	createExecutor(String timerThreadNamePrefix, boolean daemon) Provides ScheduledExecutorService instance used for execution.
protected abstract Runnable	createTask() This method must be overriden to return the Runnable task for periodic execution by this class.
int	getFirstExecutionDelaySeconds() Delay of first task execution in seconds.
int	getTaskIntervalSeconds() Returns time interval at which task is executed (in seconds).
String	getTimerThreadNamePrefix() The prefix name given to all threads associated with the underlying time.
boolean	isDaemon() Whether the daemon or non-daemon threads should be used.
boolean	isFixedDelay() Whether this instance will run its task at a fixed delay or a fixed rate; by default this class uses a fixed rate.
boolean	isStarted() Returns whether this instance is currently running, i.e start() has been called more recently than stop().
boolean	isTaskStarted() Whether task itself is currently started.
void	setFirstExecutionDelaySeconds(int firstExecutionDelaySeconds) Delay of first task execution in seconds.
void	setTaskIntervalSeconds(int taskIntervalSeconds) Sets time interval at which task is executed (in seconds); task execution is disabled if this is non-positive.
protected void	shutdownExecutor(ScheduledExecutorService executor) Shutdown the ScheduledExecutorService instance (that produced by createExecutor()) via executor.shutdown().
void	start() Start periodic background execution of task.
void	startTask() Called by start() and by setTaskIntervalSeconds() when necessary.
void	stop() Stop periodic background execution of task.
void	stopTask() Called by stop() and by setTaskIntervalSeconds() when necessary.

Methods inherited from class java.lang.Object

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

Constructor Detail

PeriodicTaskSupport

public PeriodicTaskSupport()

Default constructor

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(int taskIntervalSeconds)

Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(String timerThreadNamePrefix)

Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(String timerThreadNamePrefix,
                           int taskIntervalSeconds)

Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(boolean daemon)

Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(boolean daemon,
                           int taskIntervalSeconds)

Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(String timerThreadNamePrefix,
                           boolean daemon)

Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(String timerThreadNamePrefix,
                           boolean daemon,
                           int taskIntervalSeconds)

Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(String timerThreadNamePrefix,
                           boolean daemon,
                           int taskIntervalSeconds,
                           int firstExecutionDelaySeconds)

Constructor; arguments set corresponding properties

Supported API: true

PeriodicTaskSupport

public PeriodicTaskSupport(String timerThreadNamePrefix,
                           boolean daemon,
                           int taskIntervalSeconds,
                           int firstExecutionDelaySeconds,
                           boolean fixedDelay)

Constructor; arguments set corresponding properties

Supported API: true

Method Detail

createTask

protected abstract Runnable createTask()

This method must be overriden to return the Runnable task for periodic execution by this class.

Supported API: true

isStarted

public boolean isStarted()

Returns whether this instance is currently running, i.e start() has been called more recently than stop().

Supported API: true

start

public void start()

Start periodic background execution of task. When used from within an SelfAwareMBean this should generally be called within the MBean's start() method.

Supported API: true

stop

public void stop()

Stop periodic background execution of task. When used from within an SelfAwareMBean this should generally be called within the MBean's stop() method.

Supported API: true

getTaskIntervalSeconds

public int getTaskIntervalSeconds()

Returns time interval at which task is executed (in seconds).

Supported API: true

setTaskIntervalSeconds

public void setTaskIntervalSeconds(int taskIntervalSeconds)

Sets time interval at which task is executed (in seconds); task execution is disabled if this is non-positive.

Supported API: true

getFirstExecutionDelaySeconds

public int getFirstExecutionDelaySeconds()

Delay of first task execution in seconds. A negative value implies that the taskIntervalSeconds will be used instead.

Supported API: true

setFirstExecutionDelaySeconds

public void setFirstExecutionDelaySeconds(int firstExecutionDelaySeconds)

Delay of first task execution in seconds. A negative value implies that the taskIntervalSeconds will be used instead.

Note that calling this method has no effect on this instance while it is in a started/running state, but will have an effect the next time the task is restarted (including upon a call to setTaskIntervalSeconds()).

Supported API: true

getTimerThreadNamePrefix

public String getTimerThreadNamePrefix()

The prefix name given to all threads associated with the underlying time. This prefix is used with an underlying SharedScheduledExecutor to share thread pools for all instances with the same prefix name and daemon flag. A value of null here implies that a default prefix will be used in SharedScheduledExecutor.

Supported API: true

isDaemon

public boolean isDaemon()

Whether the daemon or non-daemon threads should be used.

Supported API: true

isFixedDelay

public boolean isFixedDelay()

Whether this instance will run its task at a fixed delay or a fixed rate; by default this class uses a fixed rate.

Supported API: true

isTaskStarted

public boolean isTaskStarted()

Whether task itself is currently started.

Supported API: true

startTask

public void startTask()

Called by start() and by setTaskIntervalSeconds() when necessary. Should only need to be called directly when something else causes a need to temporarily pause and restart the task. This is more efficient than calling stop and then start.

Warning: This routine is a no-op when this object is not started (see start() and isStarted()).

Supported API: true

stopTask

public void stopTask()

Called by stop() and by setTaskIntervalSeconds() when necessary. Should only need to be called directly when something else causes a need to temporarily pause and restart the task. This is more efficient than calling stop and then start.

Supported API: true

createExecutor

protected ScheduledExecutorService createExecutor(String timerThreadNamePrefix,
                                                  boolean daemon)

Provides ScheduledExecutorService instance used for execution. This implementation returns a SharedScheduledExecutor and should almost always suffice as is.

Supported API: true

shutdownExecutor

protected void shutdownExecutor(ScheduledExecutorService executor)

Shutdown the ScheduledExecutorService instance (that produced by createExecutor()) via executor.shutdown(). This implementation returns a SharedScheduledExecutor and should almost always suffice as is.

Supported API: true