stella.io

Class PollingRS485Server.Poller

java.lang.Object

java.util.TimerTask

stella.io.PollingRS485Server.Poller

All Implemented Interfaces:

Runnable

Enclosing class:

PollingRS485Server

protected class PollingRS485Server.Poller
extends TimerTask

The polling timer task. Once started this thread writes a command to the serial server and block-reads the return value. This return value is then stored in the embedding class's chache. After one value has been retrieved this thread is rescheduled after a certain time, specified by PollingRS485Server.KEY_POLLBASE. To allow different read-out times in active and passive states, the poller drops some read cycles, depending on PollingRS485Server.KEY_ACTIVEDROP and PollingRS485Server.KEY_PASSIVEDROP.

Field Summary

Fields

Modifier and Type	Field and Description
private Triggering	cycle True if polling is retrieving data.
private int	dropcycle The dropping counter.
private int	listindex The actual index in the list.
private Object	monitor An object to notify on the start of each run.
private int	polldrop The actual polldrop of the poller.
private List	pollist The actual poller's list of keys to poll.
private boolean	running True if poller is running.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Poller() Constructs a new polling thread.

Method Summary

Modifier and Type	Method and Description
boolean	cancel() Cancels this polling thread.
boolean	isRunning() Returns the status of the running flag.
private void	notifyCacheList(String key, String newval) Notifies all listeners subscribed to the specified key.
void	run() The run method of the poller.
private void	setMonitor(Object mon) Sets an object that should be notified at the start of each run cycle.
protected void	setPollingDrop(int newdrop) Sets the list of command this poller should query.
protected void	setPollingList(List newlist) Sets the list of command this poller should query.

Methods inherited from class java.util.TimerTask

scheduledExecutionTime

Methods inherited from class java.lang.Object

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

Field Detail

pollist

private List pollist

The actual poller's list of keys to poll.

listindex

private int listindex

The actual index in the list.

polldrop

private int polldrop

The actual polldrop of the poller.

dropcycle

private int dropcycle

The dropping counter. If polldrop is reached, a read is performed.

cycle

private final Triggering cycle

True if polling is retrieving data. Object to synchronize on it.

running

private boolean running

True if poller is running.

monitor

private Object monitor

An object to notify on the start of each run.

Constructor Detail

Poller

protected Poller()
          throws InitException

Constructs a new polling thread. Does not start automatically.

Throws:

InitException

Method Detail

setMonitor

private void setMonitor(Object mon)

Sets an object that should be notified at the start of each run cycle. If called with a null argument, notification is reset.

run

public void run()

The run method of the poller. Per cycle one command string is read from the pollers actual command list. It is writtn as a command to the serial port and the answer block-reads into the cache. This thread then waits for the actual polling time before starting the next cycle with the next command.
Changes in the cached value are reported to registered CacheChangedListeners. The null element is allowed in the cache and may even spark the listener's notification.

A call to cancel() allows this thread to die.

Specified by:

run in interface Runnable

Specified by:

run in class TimerTask

cancel

public boolean cancel()

Cancels this polling thread. The thread should die within a time determined by PollingRS485Server.KEY_POLLBASE multiplied by the current drop rate.

Overrides:

cancel in class TimerTask

isRunning

public boolean isRunning()

Returns the status of the running flag. The poller is considered running if it was scheduled for at least one time and has not been canceled since.

setPollingList

protected void setPollingList(List newlist)

Sets the list of command this poller should query. Warning: this method is not synchronized. If called during the live-time of the poller, external synchronization on the poller's cache is necessary.

setPollingDrop

protected void setPollingDrop(int newdrop)

Sets the list of command this poller should query. Warning: this method is not synchronized. If called during the live-time of the poller, external synchronization on the poller's cache is necessary because setting a primitive long must not be atomic.

notifyCacheList

private void notifyCacheList(String key,
                             String newval)

Notifies all listeners subscribed to the specified key. The calling method ensures that the cache value has changed, so no checks are performed here.