stella.net

Class AbstractVariableMonitor

java.lang.Object

stella.net.AbstractVariableMonitor

All Implemented Interfaces:

CacheCaster, CacheChangedCaster

Direct Known Subclasses:

AdsVariableMonitor, PreRecordedMonitor

public abstract class AbstractVariableMonitor
extends Object
implements CacheChangedCaster, CacheCaster

Author:

wooz

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private class	AbstractVariableMonitor.Update The repetitive task that refreshes the variables, updates the internal cache and notifies listeners on cache changes.

Field Summary

Fields

Modifier and Type	Field and Description
private Map<String,Object>	cache The actual cache.
private Timer	clock Used for polling the variable list at fixed delay.
private Map<String,Set<CacheChangedListener>>	ears A set of listeners for changes on variables values per name.
private Object	lock If non-null, notified after each poll.
private AbstractVariableMonitor.Update	poll The polling timer task.
private Set<CacheListener>	polling The cache listeners.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractVariableMonitor() Constructor chaining.

Method Summary

Modifier and Type	Method and Description
void	addCacheChangedListener(CacheChangedListener ccl, String key) Adds a new cache changed listener to this polling instance.
void	addCacheListener(CacheListener ear) Adds a new cache changed listener to this polling instance.
boolean	addMonitoring(Collection<String> vars) Adds this list of variables to the monitor.
Collection<String>	getMonitored() Returns all currently monitored variable names.
Object	getVariable(String name) Returns the lately cached value of the variable of the provided name.
boolean	isRunning() Returns true, if the polling is in progress.
private void	notifyListeners(CacheChangedEvent cce, Collection<CacheChangedListener> signal) Synchronizes on the listeners and notifies each of a cache changed event.
protected abstract Map<String,Object>	refreshVariables(Collection<String> vars) This method actually does the read-in of the variables.
void	removeCacheChangedListener(CacheChangedListener ear, String key) Removes a cache changed listener from this polling instance.
void	removeCacheListener(CacheListener ear) Removes a cache changed listener from this polling instance.
int	removeMonitoring(Collection<String> vars) Removes the list of variables from the monitoring
void	setLock(Object lock)
void	startMonitoring(long delay, long period) Starts monitoring of all variables.
void	stopMonitoring() Stops cache refreshing.

Methods inherited from class java.lang.Object

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

Field Detail

clock

private Timer clock

Used for polling the variable list at fixed delay.

cache

private final Map<String,Object> cache

The actual cache.

polling

private final Set<CacheListener> polling

The cache listeners.

ears

private Map<String,Set<CacheChangedListener>> ears

A set of listeners for changes on variables values per name.

poll

private AbstractVariableMonitor.Update poll

The polling timer task.

lock

private Object lock

If non-null, notified after each poll.

Constructor Detail

AbstractVariableMonitor

protected AbstractVariableMonitor()

Constructor chaining.

Method Detail

addCacheListener

public void addCacheListener(CacheListener ear)

Adds a new cache changed listener to this polling instance. /* (non-Javadoc)

Specified by:

addCacheListener in interface CacheCaster

Parameters:

ear - The listener to be notified when the cache value changes.

See Also:

CacheCaster.addCacheListener(stella.io.CacheListener)

removeCacheListener

public void removeCacheListener(CacheListener ear)

Removes a cache changed listener from this polling instance. (non-Javadoc)

Specified by:

removeCacheListener in interface CacheCaster

Parameters:

ear - The listener to be notified when the cache value changes.

See Also:

CacheCaster.removeCacheListener(stella.io.CacheListener)

addCacheChangedListener

public void addCacheChangedListener(CacheChangedListener ccl,
                                    String key)

Adds a new cache changed listener to this polling instance. Note that registering to keys that are not actually polled is allowed. Additionally, if the listening key is present in the cache and mapped to a value different then null, the listener is immediately notified of a cache change.

Specified by:

addCacheChangedListener in interface CacheChangedCaster

Parameters:

ccl - The listener to be notified when the cache value changes.

key - The serial command this listenr is interested in.

removeCacheChangedListener

public void removeCacheChangedListener(CacheChangedListener ear,
                                       String key)

Removes a cache changed listener from this polling instance. If the listener has not been registered, nothing changes.

Specified by:

removeCacheChangedListener in interface CacheChangedCaster

Parameters:

ear - The listener to be notified when the cache value changes.

key - The serial command this listenr is interested in.

notifyListeners

private void notifyListeners(CacheChangedEvent cce,
                             Collection<CacheChangedListener> signal)

Synchronizes on the listeners and notifies each of a cache changed event.

Parameters:

cce - The cache changed event created during polling

signal - The list of registered listeners for the events variable name.

refreshVariables

protected abstract Map<String,Object> refreshVariables(Collection<String> vars)

This method actually does the read-in of the variables. Depending on the source, this may include serial or network access, but may also relate to memory variable only.

Parameters:

vars - Names of all variables that should be refreshed

Returns:

A mapping of variable names to their current values.

addMonitoring

public boolean addMonitoring(Collection<String> vars)

Adds this list of variables to the monitor. If called during an active monitoring, the values of the new variables stay null until the first polling after the add occurs.

Parameters:

vars -

Returns:

removeMonitoring

public int removeMonitoring(Collection<String> vars)

Removes the list of variables from the monitoring

Parameters:

vars -

Returns:

The number of variables actually removed.

getMonitored

public Collection<String> getMonitored()

Returns all currently monitored variable names.

Returns:

getVariable

public Object getVariable(String name)

Returns the lately cached value of the variable of the provided name. Returns null if the cache is empty or if the variable is unknown (or if the variable allows null values and is indeed currently null).

Parameters:

name - The variables name

Returns:

Its current value from the cache.

setLock

public void setLock(Object lock)

Parameters:

lock - the lock to set

startMonitoring

public void startMonitoring(long delay,
                            long period)

Starts monitoring of all variables. Later adding of variables is possible, which will then immediately receive new values on the normal polling time.

stopMonitoring

public void stopMonitoring()

Stops cache refreshing. All variables sustain their last read-out values. Once this method returns, no further calls to refreshVariables(Collection) will occur, thus underlying driver can savely be closed.

isRunning

public boolean isRunning()

Returns true, if the polling is in progress.