globals.rmi

Class ParameterStub

java.lang.Object

util.PropertyContainer

util.PropertyResources

globals.parameter.AbstractParameter

globals.rmi.ParameterStub

All Implemented Interfaces:

Parameter, Cloneable, Runnable, Remote, CancelRunnable, ExitCleaning, Initializable, PropertySupplying, Reloadable, ResourceSupplying, RmiListener

Direct Known Subclasses:

AcquireOffsetStub, FitsParameterStub, TriggerStub, ValueStub

public class ParameterStub
extends AbstractParameter
implements CancelRunnable, RmiListener, Reloadable

The stub to a remote parameter. To allow local access to all paramters, a remote parameter is served by this stub. On construct this stub starts a thread within it tries to register to its remote counterpart. If binding is impossible this stub tries to re-establish contact after a waiting period defined in the properties. Only after a certain number of unsuccessful tries, the run method exits. Note that due to the data event listening schema it is not feasable to register to the remote sensor whenever data is needed.

Note that this globals get() method blocks until this registering thread dies to ensure proper functionality.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ParameterStub.Finger A class that allows access to parameter skeletons.

Nested classes/interfaces inherited from class util.PropertyResources

PropertyResources.Load, PropertyResources.URLResource

Field Summary

Fields

Modifier and Type	Field and Description
private Thread	bind A reference to the registering thread.
private boolean	cancel The cancel flag for the binding thread.
private static boolean	DEFBLOCK The default blocking behaviour.
private static int	DEFINITTRY The default initial tries number (1000).
private static int	DEFRETRY The default retries number (10).
private static long	DEFSERVERDELAY The default delay on server exit rebinds.
private static long	DEFWAIT The default waiting time-out between registering retries (1000ms).
private long	delay A delay for the binding thread to execute.
private Format	format A formatter for the remopte object received.
static String	KEY_BLOCK If true, get() blocks on retries.
static String	KEY_FORMATCLASS The key to the class name of the format to use.
static String	KEY_FORMATPATTERN The key to the format string constructor to use.
static String	KEY_INITTRY The key linked to the number of initial registering tries.
static String	KEY_REMOTENAME The key pointing to the name of the remote reference to bind to.
static String	KEY_RETRY The key linked to the number of registering retries.
static String	KEY_SERVERDELAY The key linked to a delay for binding on server exit.
static String	KEY_WAIT The key linked to the time-out between registering retries.
private int	retry The current number of retries.
protected RemoteParameter	sensor The remote instance of the sensor global.

Fields inherited from class globals.parameter.AbstractParameter

KEY_FORMAT, KEY_NAME, KEY_PRESERVE, UNKNOWN

Fields inherited from class util.PropertyResources

KEY_NOINITONCREATE, POSTFIX_ALPHABET, POSTFIX_BYTES, POSTFIX_DIR, POSTFIX_EXT, POSTFIX_FILE, POSTFIX_LIST, POSTFIX_MODTIME, POSTFIX_URL

Fields inherited from class util.PropertyContainer

KEY_LISTSEPARATOR, KEY_MAPKEYVALUECHAR, KEY_MAPSEPARATOR

Fields inherited from interface util.PropertySupplying

CONFIG, KEY_CLASS

Fields inherited from interface util.ResourceSupplying

KEY_URLRESOURCES, KEY_URLUSECONFIG, KEY_URLUSECURRENT, KEY_URLUSEHOME

Constructor Summary

Constructors

Constructor and Description
ParameterStub(Map<String,String> prop) Constructs a new paramter stub.
ParameterStub(String remotename) For convenience, we support a constructor with only the remote name.

Method Summary

Modifier and Type	Method and Description
private void	bindToRemote(int retries, long timeout) Tries to bind to the remote paramter.
void	cancel() Cancels the binding thread.
void	disconnect(RmiCaster name) Called by the remote parameter if it will stop serve.
void	exit() If we preserve our state, we do this at exit.
Object	get() Gets the value of the remotely wrapped global.
Thread	getAsociatedThread() Returns the binding thread.
String	getFormatted() Tries to format the remote object received according to its formatter.
void	init() Initializes the parameter stub by binding it to the remote reference.
boolean	isConnected() Returns true if sensor is non-null.
long	maxTimeToCancel() Returns the maximum time required for canceling the binding thread.
protected void	rebind() Daughter access after initial binding.
double	rescanned(String key, String old, String newval) If the binding name, KEY_REMOTENAME cahnged, we deregister if we are connected and restart the binding process.
void	run() Tries to register to a remote sensor global.
Object	set(Object val) Setting a sensor value is not allowed.

Methods inherited from class globals.parameter.AbstractParameter

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

Methods inherited from class util.PropertyResources

clone, createFrom, createFrom, createFrom, createInstance, getApplet, getAsResources, getLocate, getPropertiesToKey, getPropertiesToKey, getResource, getResourceAsStream, getResourceFromKey, getResources, hasLocalURLs, initProperties, keyCreate, keyCreate, reload, setApplet

Methods inherited from class util.PropertyContainer

augment, augment, augment, augment, augment, defaultBoolean, defaultChar, defaultDouble, defaultFloat, defaultInt, defaultLong, defaultObject, defaultObject, defaultProperties, defaultProperty, getAsBoolean, getAsChar, getAsDouble, getAsEnums, getAsFloat, getAsInt, getAsList, getAsLong, getAsMap, getAsMap, getAsObject, getAsObject, getProperties, getProperty, has, isNew, parseObject, parseObject, reload, removeProperty, requires, setObject, setProperties, setProperty, stringProperties

Methods inherited from class java.lang.Object

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

Methods inherited from interface util.Reloadable

reload

Methods inherited from interface util.PropertySupplying

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

Field Detail

KEY_REMOTENAME

public static final String KEY_REMOTENAME

The key pointing to the name of the remote reference to bind to.

See Also:

Constant Field Values

KEY_BLOCK

public static final String KEY_BLOCK

If true, get() blocks on retries.

See Also:

Constant Field Values

KEY_WAIT

public static final String KEY_WAIT

The key linked to the time-out between registering retries.

See Also:

Constant Field Values

KEY_RETRY

public static final String KEY_RETRY

The key linked to the number of registering retries.

See Also:

Constant Field Values

KEY_INITTRY

public static final String KEY_INITTRY

The key linked to the number of initial registering tries.

See Also:

Constant Field Values

KEY_SERVERDELAY

public static final String KEY_SERVERDELAY

The key linked to a delay for binding on server exit.

See Also:

Constant Field Values

KEY_FORMATCLASS

public static final String KEY_FORMATCLASS

The key to the class name of the format to use.

See Also:

Constant Field Values

KEY_FORMATPATTERN

public static final String KEY_FORMATPATTERN

The key to the format string constructor to use.

See Also:

Constant Field Values

DEFBLOCK

private static final boolean DEFBLOCK

The default blocking behaviour.

See Also:

Constant Field Values

DEFWAIT

private static final long DEFWAIT

The default waiting time-out between registering retries (1000ms).

See Also:

Constant Field Values

DEFRETRY

private static final int DEFRETRY

The default retries number (10).

See Also:

Constant Field Values

DEFSERVERDELAY

private static final long DEFSERVERDELAY

The default delay on server exit rebinds.

See Also:

Constant Field Values

DEFINITTRY

private static final int DEFINITTRY

The default initial tries number (1000).

See Also:

Constant Field Values

sensor

protected RemoteParameter sensor

The remote instance of the sensor global.

bind

private Thread bind

A reference to the registering thread.

retry

private int retry

The current number of retries.

delay

private long delay

A delay for the binding thread to execute.

cancel

private boolean cancel

The cancel flag for the binding thread.

format

private Format format

A formatter for the remopte object received.

Constructor Detail

ParameterStub

public ParameterStub(String remotename)
              throws RemoteException,
                     InitException

For convenience, we support a constructor with only the remote name. This constructor also initiates the binding process with a call to init().

Throws:

InitException

RemoteException

ParameterStub

public ParameterStub(Map<String,String> prop)
              throws RemoteException

Constructs a new paramter stub. This means the parameter tries to register at a RemoteParameter. If the remote counterpart is not yet bound, a retry loop, defined with KEY_RETRY and KEY_WAIT is started during which the parameter waits for the server to come up.

Throws:

RemoteException

Method Detail

init

public void init()
          throws InitException

Initializes the parameter stub by binding it to the remote reference.

Specified by:

init in interface Initializable

Overrides:

init in class AbstractParameter

Throws:

InitException

exit

public void exit()

Description copied from class: AbstractParameter

If we preserve our state, we do this at exit.

Specified by:

exit in interface ExitCleaning

Overrides:

exit in class AbstractParameter

bindToRemote

private void bindToRemote(int retries,
                          long timeout)

Tries to bind to the remote paramter. Does this with a thread that re-initiates registry lookup if unsuccessful.

run

public void run()

Tries to register to a remote sensor global. The #KEY_REMOTE is used to locate the registry on the remote machine. Then, the remote registry is querried for a remote object with the name given by the KEY_REMOTENAME, augmented with the naming extension defined in RemoteParameter#NAMING_EXTENSION. If a remote reference is obtained and is convertable into a remote global instance this thread dies. Otherwise a retires cycle (see KEY_RETRY for number of retires ) with a sleeping period defined by KEY_WAIT is entered.

Note that querrying this global is only permitted if this thread has died, i.e. if registering was successful.

Specified by:

run in interface Runnable

rescanned

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

If the binding name, KEY_REMOTENAME cahnged, we deregister if we are connected and restart the binding process.

Specified by:

rescanned in interface Reloadable

Overrides:

rescanned in class AbstractParameter

isConnected

public boolean isConnected()
                    throws RemoteException

Returns true if sensor is non-null.

Specified by:

isConnected in interface RmiListener

Throws:

RemoteException

disconnect

public void disconnect(RmiCaster name)
                throws RemoteException

Called by the remote parameter if it will stop serve. There is always only a single server, thus we ignore the name.

Specified by:

disconnect in interface RmiListener

Throws:

RemoteException

cancel

public void cancel()

Cancels the binding thread. Used on exit, if rebinding is in process. Also deletes itself from the server parameter.

Specified by:

cancel in interface CancelRunnable

maxTimeToCancel

public long maxTimeToCancel()

Returns the maximum time required for canceling the binding thread.

Specified by:

maxTimeToCancel in interface CancelRunnable

getAsociatedThread

public Thread getAsociatedThread()

Returns the binding thread. May be null.

Specified by:

getAsociatedThread in interface CancelRunnable

get

public Object get()

Gets the value of the remotely wrapped global. If the registering thread is still running this method blocks until it is finished. If the remote skeleton wraps a sensor the get method is likely to block, too, until data is available. If the reference to the remote parameter has become invalid between initial binding and current data retrieval, binding is again initiated. Only if the binding cannot be completed successfully, null is returned.

Specified by:

get in interface Parameter

rebind

protected void rebind()

Daughter access after initial binding.

set

public Object set(Object val)

Setting a sensor value is not allowed.

Specified by:

set in interface Parameter

Returns:

The previous value of this parameter.

getFormatted

public String getFormatted()

Tries to format the remote object received according to its formatter. For the special case that the object received is a Long and the formatter specified is a DateFormat, then a new Date object is constructed from the long value received and formatted accordingly. If no format is specified, the toString method is used.

Specified by:

getFormatted in interface Parameter

Overrides:

getFormatted in class AbstractParameter