stella.parameter
Class AbstractStatusRequestor

java.lang.Object
  util.PropertyContainer
      stella.parameter.AbstractParameter
          stella.parameter.AbstractCachedParameter
              stella.parameter.AbstractStatusRequestor

All Implemented Interfaces:

Cloneable, ErrorDependingParameter, Parameter, StatusRequesting, ExitCleaning, Initializable, PropertyBearing

Direct Known Subclasses:

AltTelescope, AzTelescope, FocusPosition, MirrorTemperature, PowerTelescope, TelescopeError

public abstract class AbstractStatusRequestor
extends AbstractCachedParameter
implements StatusRequesting

An abstract base class providing the functionalibility of a StatusRequesting parameter. The KEY_COMMAND points to the class name of the command that is to be sent for an update of this parameter value. The AbstractCachedParameter.KEY_CACHE points to the time (in ms) the cached value stays valid.

Nested Class Summary

Nested classes/interfaces inherited from class util.PropertyContainer

PropertyContainer.URLResource

Field Summary

private static boolean	DEFDISABLE The default disable behaviour.
private static long	DEFTIMEOUT The default status-request maximum time.
static String	KEY_COMMAND The name of the command class to send for an update.
static String	KEY_DISABLE The key pointing to true if command sending is disabled.
static String	KEY_TIMEOUT The max.
private static Object	lock A lock object to delay the AbstractCachedParameter.get() method until update occured.
private CommandLaunching	server The command launcher that takes the urge command.
private CommandEvent	urge The command to send that urges a status message sent back.

Fields inherited from class stella.parameter.AbstractCachedParameter

KEY_CACHE

Fields inherited from class stella.parameter.AbstractParameter

KEY_FORMAT, KEY_NAME, KEY_PRESERVE, UNKNOWN

Fields inherited from class util.PropertyContainer

KEY_LISTSEPARATOR, KEY_LOCALECOUNTRY, KEY_LOCALELANGUAGE, KEY_MAPKEYVALUECHAR, KEY_MAPSEPARATOR, KEY_NOINITONCREATE, KEY_RESOURCEBUNDLES

Fields inherited from interface stella.ErrorDependingParameter

NAMING_EXTENSION

Fields inherited from interface util.PropertyBearing

CONFIG, KEY_CLASS, KEY_URLRESOURCES, KEY_URLUSECONFIG, KEY_URLUSECURRENT, KEY_URLUSEHOME

Constructor Summary

protected

AbstractStatusRequestor(Map<String,String> prop) Constructs a new status requestor.

Method Summary

protected Object	getUncached() Gets this parameter value.
void	init() Inits the status requestor.
private CommandEvent	instantiateUrge(String comname) Tries to instantiate the command that should be sent to the command handling instance.
protected abstract boolean	isStatusRequested(ErrorEvent ee) Returns true, if the error event received is of the correct type for this parameter.
void	registerError(ErrorEvent ee) Test, if the error event received is the correct error event via a call to isStatusRequested(stella.ErrorEvent).
boolean	registerLauncher(CommandLaunching launch) Registers a command launcher.
protected double	rescanned(String key, String old, String newval) If the bind property changed, we deregister from our current binding and re-instantiate a new binding thread.

Methods inherited from class stella.parameter.AbstractCachedParameter

get, getCache, getCacheFormatted, set

Methods inherited from class stella.parameter.AbstractParameter

createParameter, delivers, exit, getFormatted, getFormatted, getName, getPreserveFile, getString, getString, register, setName, toString

Methods inherited from class util.PropertyContainer

augment, augment, augment, clone, createFrom, createFrom, createFrom, defaultBoolean, defaultChar, defaultDouble, defaultFloat, defaultInt, defaultLong, defaultObject, defaultObject, defaultProperties, defaultProperty, getAsBoolean, getAsChar, getAsDouble, getAsEnums, getAsFloat, getAsInt, getAsList, getAsLong, getAsMap, getAsMap, getAsObject, getAsObject, getLocalClassLoader, getLocalized, getLocalized, getLocalizedString, getLocalizedString, getProperties, getPropertiesToKey, getPropertiesToKey, getProperty, getResource, getResourceAsStream, getResourceFromKey, getResources, has, isNew, keyCreate, keyCreate, parseObject, reload, reload, removeProperty, setObject, setProperties, setProperty, stringProperties

Methods inherited from class java.lang.Object

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

Methods inherited from interface stella.StatusRequesting

getCache, getCacheFormatted

Methods inherited from interface stella.ErrorDependingParameter

getForError

Methods inherited from interface stella.Parameter

get, getFormatted, getName, getString, set

Methods inherited from interface util.PropertyBearing

defaultBoolean, defaultChar, defaultDouble, defaultFloat, defaultInt, defaultLong, defaultObject, defaultObject, defaultProperties, defaultProperty, getAsBoolean, getAsChar, getAsDouble, getAsFloat, getAsInt, getAsList, getAsLong, getAsMap, getAsObject, getAsObject, getLocalized, getProperties, getProperty, getResource, getResourceAsStream, getResources, has, parseObject, removeProperty, setObject, setProperty, stringProperties

Field Detail

KEY_COMMAND

public static final String KEY_COMMAND

The name of the command class to send for an update.

See Also:

Constant Field Values

KEY_DISABLE

public static final String KEY_DISABLE

The key pointing to true if command sending is disabled.

See Also:

Constant Field Values

KEY_TIMEOUT

public static final String KEY_TIMEOUT

The max. wait time for status receive.

See Also:

Constant Field Values

DEFDISABLE

private static final boolean DEFDISABLE

The default disable behaviour.

See Also:

Constant Field Values

DEFTIMEOUT

private static final long DEFTIMEOUT

The default status-request maximum time.

See Also:

Constant Field Values

urge

private CommandEvent urge

The command to send that urges a status message sent back.

server

private CommandLaunching server

The command launcher that takes the urge command.

lock

private static Object lock

A lock object to delay the AbstractCachedParameter.get() method until update occured.

Constructor Detail

AbstractStatusRequestor

protected AbstractStatusRequestor(Map<String,String> prop)

Constructs a new status requestor. Throws an IllegalArgumentException if the KEY_COMMAND class is not found or cannot be used to instantiate a CommandEvent. The cache time and the disable flag are defaulted.

Method Detail

init

public void init()

Inits the status requestor. This is delayed from construction because of possible default settings for KEY_COMMAND in daughter classes.

Specified by:

init in interface Initializable

Overrides:

init in class AbstractParameter

instantiateUrge

private CommandEvent instantiateUrge(String comname)

Tries to instantiate the command that should be sent to the command handling instance. Stores the command in urge as well as returning it.

rescanned

protected double rescanned(String key,
                           String old,
                           String newval)

If the bind property changed, we deregister from our current binding and re-instantiate a new binding thread.

Overrides:

rescanned in class AbstractParameter

registerLauncher

public boolean registerLauncher(CommandLaunching launch)

Registers a command launcher. If the launcher handles commands of the type of urge it is recognized as the correct launcher. Only then, true is returned.

Specified by:

registerLauncher in interface StatusRequesting

Returns:

True, if this is the coorect command launcher.

getUncached

protected Object getUncached()

Gets this parameter value. If the cache is up-to-date, the cached value is returned. Otherwise, the urge command is sent to the registered command launcher server. The method now waits on the error event returned from the server. As soon as this error event is received in the registerError(stella.ErrorEvent) method, the cache is updated and the value returned.
For parameters that link to the same command, the KEY_DISABLE flag is introduced. If this is set to true, command sending is prevented, and the cache value is returned. This is only useful, if at least two parameters listen to the same status event. Then, only the parameter with the shortest cache time should carry a non-disabled flag. It is important to avoid dead-lock situations by using different cache times on these parameters. Keep in mind that all parameters will be updated at the highest frequency, regardless

Specified by:

getUncached in class AbstractCachedParameter

registerError

public void registerError(ErrorEvent ee)

Test, if the error event received is the correct error event via a call to isStatusRequested(stella.ErrorEvent). If so, the #getFor method is called and the cache is updated with the value returned.

Specified by:

registerError in interface ErrorDependingParameter

isStatusRequested

protected abstract boolean isStatusRequested(ErrorEvent ee)

Returns true, if the error event received is of the correct type for this parameter.