net.sf.basedb.core.signal
Class AbstractSignalReceiver

java.lang.Object
  net.sf.basedb.core.signal.AbstractSignalReceiver

All Implemented Interfaces:

SignalReceiver

Direct Known Subclasses:

LocalSignalReceiver, SocketSignalReceiver

public abstract class AbstractSignalReceiver
extends Object
implements SignalReceiver

Abstract base class that is useful when implementing signal receivers. This class helps with keeping track of signal handlers and with generating return values for the registerSignalHandler(SignalHandler) method. This class will generate values in the form of URI:s. signal://handlerId@receiverId/?supportedSignals.

• The receiverId part is given by the parameter in the init(String) method and must be set by the implementing subclass.
• The handlerId part is given by calling getLocalSignalHandlerId(SignalHandler). This method may be overridden by subclasses that needs a different method of local ID generation. The important thing is that the ID is unique among all registered signal handlers.
• The supportedSignals part is created by joining all signal ID:s from SignalHandler.getSupportedSignals() into a comma-separated string.

The AbstractSignalTransporter contains methods for parsing this scheme and make the information available to subclasses as a URI and as higher-level objects.

Subclasses should override the getGlobalSignalId(SignalHandler) if they want to use a different ID generation scheme.

Version:

2.6

Author:

nicklas

Last modified

$Date: 2010-09-02 14:09:15 +0200 (Thu, 02 Sep 2010) $

Field Summary

private Map<String,SignalHandler>	handlers Maps local signal handler ID to -> signal handler itself.
private static Logger	logger Log signals processing.
private Thread	notifyThread
private String	receiverId

Constructor Summary

protected

AbstractSignalReceiver() Create a new signal receiver.

Method Summary

void	close(int wait) Close this signal receiver.
protected String	getGlobalSignalId(SignalHandler handler) Generate a signal ID string.
protected String	getLocalSignalHandlerId(SignalHandler handler) Get the local signal handler id of the given signal handler.
protected String	getReceiverId() Get the receiver ID that was passed to the init(String) method.
protected SignalHandler	getSignalHandler(String localId) Get the signal handler with a given ID.
void	init(String receiverId) Initialise the signal receiver.
protected void	processSignalMessage(String message) Process a signal message.
String	registerSignalHandler(SignalHandler handler) Register a signal handler with this receiver.
void	sendToAll(Signal signal) Deprecated. In 2.16, use sendToAll(SignalSender) instead
void	sendToAll(SignalSender sender) Let the signal sender send one or more signals to all registered signal handlers on this reciever.
void	unregisterSignalHandler(SignalHandler handler) Unregister a signal handler.

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.basedb.core.signal.SignalReceiver

getSignalTransporterClass

Field Detail

logger

private static final Logger logger

Log signals processing.

handlers

private Map<String,SignalHandler> handlers

Maps local signal handler ID to -> signal handler itself.

receiverId

private String receiverId

notifyThread

private Thread notifyThread

Constructor Detail

AbstractSignalReceiver

protected AbstractSignalReceiver()

Create a new signal receiver.

Method Detail

init

public void init(String receiverId)

Initialise the signal receiver.

Specified by:

init in interface SignalReceiver

Parameters:

receiverId - The ID of the signal receiver, needed if the default ID generation should be used

close

public void close(int wait)

Close this signal receiver. If a subclass overrides this method it should call super.close() if it wants to use the default shutdown notification to signal handlers. This implementation will start a separate notification thread that first sends the Signal.SHUTDOWN signal to all registered handlers, and then Signal.ABORT signal to all that are still alive after the shutdown signal. The current thread will wait at most the given time. If the number of registered handlers goes down to 0 before the time has ended the current thread will be awakened so it can continue. Note that the notification thread will usually finish in a short time, but it may take longer for all worker thread of each job to react to the signal.

Specified by:

close in interface SignalReceiver

Parameters:

wait - Number of milliseconds to wait for registered jobs to abort, use a negative value to disable notification, and 0 to disable waiting

registerSignalHandler

public String registerSignalHandler(SignalHandler handler)

Register a signal handler with this receiver.

Specified by:

registerSignalHandler in interface SignalReceiver

Parameters:

handler - The signal handler to register

Returns:

The global ID of the signal handler

See Also:

AbstractSignalReceiver

unregisterSignalHandler

public void unregisterSignalHandler(SignalHandler handler)

Unregister a signal handler.

Specified by:

unregisterSignalHandler in interface SignalReceiver

Parameters:

handler - The signal handler to unregister

sendToAll

@Deprecated
public void sendToAll(Signal signal)

Deprecated. In 2.16, use sendToAll(SignalSender) instead

Description copied from interface: SignalReceiver

Send a signal to all registered signal handlers that supports it. The main purpose of this method is to be able to send the Signal.ABORT when the system is shutting down.

Specified by:

sendToAll in interface SignalReceiver

Parameters:

signal - The signal to send

sendToAll

public void sendToAll(SignalSender sender)

Description copied from interface: SignalReceiver

Let the signal sender send one or more signals to all registered signal handlers on this reciever.

Specified by:

sendToAll in interface SignalReceiver

Parameters:

sender - A signal sender implementation

getReceiverId

protected String getReceiverId()

Get the receiver ID that was passed to the init(String) method.

getGlobalSignalId

protected String getGlobalSignalId(SignalHandler handler)

Generate a signal ID string. This string is returned by the registerSignalHandler(SignalHandler) method and is used in SignalTransporter.init(String) method to initialise a transporter object so that it can send signals to the specified handler. See the class documentation for a description of the format of the generated string. The string is of the format:

signal://handlerId@receiverId/?supportedSignals

See class description for detailed information.

Parameters:

handler - The signal handler to generate the ID for

Returns:

The signal handler ID

getLocalSignalHandlerId

protected String getLocalSignalHandlerId(SignalHandler handler)

Get the local signal handler id of the given signal handler. This implementation simply return the system hashcode for the handler. The returned ID must be unique among the registered signal handlers.

Parameters:

handler - The handler to get the id for

Returns:

The local handler id

getSignalHandler

protected SignalHandler getSignalHandler(String localId)

Get the signal handler with a given ID.

Parameters:

localId - The local signal handler ID as returned by the getLocalSignalHandlerId(SignalHandler) method

Returns:

The signal handler, or null if no handler is found

processSignalMessage

protected void processSignalMessage(String message)

Process a signal message. If the message can't be understood or if no handler can be found this method does nothing. The signal will be delivered to the signal handler in the current thread.

Parameters:

message - The message to process, the format of the message must be compatible with the message that AbstractSignalTransporter.generateSignalMessage(Signal) generates