com.sun.jdmk.discovery
Class DiscoveryMonitor

java.lang.Object
  javax.management.NotificationBroadcasterSupport
      com.sun.jdmk.discovery.DiscoveryMonitor

All Implemented Interfaces:

DiscoveryMonitorMBean, Serializable, MBeanRegistration, NotificationBroadcaster, NotificationEmitter

public class DiscoveryMonitor
extends NotificationBroadcasterSupport
implements Serializable, DiscoveryMonitorMBean, MBeanRegistration

Describe an MBean that listens for registering and unregistering information sent by DiscoveryResponder objects on a given multicast group. Any agent that is to use multicast discovery must have a DiscoveryResponder registered in its MBean server. When a DiscoveryResponder is registered in an MBean server and when its start or stop methods are called, it informs the rest of the multicast group by sending a multicast message. The format of this message is not exposed. Whenever a DiscoveryMonitor receives a registration or unregistration message, it sends a DiscoveryResponderNotification to its notification listener.

A DiscoveryMonitor can be instantiated either in stand alone mode (Client side) or added to an MBean Server. In the first case, the client should call the appropriate constructor to initialize the multicastGroup and multicastPort parameters. The default values for the group and the port are 224.224.224.224 and 9000. A DiscoveryMonitor can be stopped by calling the stop method. When it is stopped, the DiscoveryMonitor no longer listens for registering and unregistering messages from DiscoveryResponder objects. A DiscoveryMonitor can be restarted by invoking the start method.

A DiscoveryMonitor has a state property which reflects its activity.

DiscoveryMonitor	State
running	ONLINE
stopped	OFFLINE
stopping	STOPPING
starting	STARTING

The transition between ONLINE and OFFLINE may not be immediate. The DiscoveryMonitor may need some time to finish or interrupt the active requests. During this time the state of the DiscoveryMonitor is STOPPING. When a DiscoveryMonitor is removed from a Java DMK agent, it is automatically stopped.

See Also:

Serialized Form

Field Summary

static int	OFFLINE Marks the "state" property as stopped.
static int	ONLINE Marks the "state" property as running.
static int	STARTING Marks the "state" property as in-transition from OFFLINE to ONLINE.
static int	STOPPING Marks the "state" property as in-transition from ONLINE to OFFLINE.

Constructor Summary

DiscoveryMonitor()
Constructs a DiscoveryMonitor.

DiscoveryMonitor(String multicastGroup, int multicastPort)
Constructs a DiscoveryMonitor.

DiscoveryMonitor(String multicastGroup, int multicastPort, InetAddress inf)
Constructs a DiscoveryMonitor.

Method Summary

String	getMulticastGroup() Returns the multicast group.
int	getMulticastPort() Returns the multicast port.
Integer	getState() Returns the state of this DiscoveryMonitor.
String	getStateString() Returns the state of this DiscoveryMonitor in string form.
void	postDeregister() Allows the MBean to perform any operations needed after having been unregistered in the MBean server.
void	postRegister(Boolean registrationDone) Allows the MBean to perform any operations needed after having been registered in the MBean server or after the registration has failed.
void	preDeregister() Allows the MBean to perform any operations it needs before being unregistered by the MBean server.
ObjectName	preRegister(MBeanServer server, ObjectName name) Allows the MBean to perform any operations it needs before being registered in the MBean server.
void	setMulticastGroup(String multicastGroup) Sets the multicast group name.
void	setMulticastPort(int multicastPort) Sets the multicast port.
void	start() Starts listening for DiscoveryResponder objects registering/unregistering.
void	stop() Stops this DiscoveryMonitor.
boolean	waitState(int state, long timeout) Waits until either the State attribute of this MBean equals the specified state parameter, or the specified timeout has elapsed.

Methods inherited from class javax.management.NotificationBroadcasterSupport

addNotificationListener, getNotificationInfo, handleNotification, removeNotificationListener, removeNotificationListener, sendNotification

Methods inherited from class java.lang.Object

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

Field Detail

ONLINE

public static final int ONLINE

Marks the "state" property as running.

See Also:

Constant Field Values

OFFLINE

public static final int OFFLINE

Marks the "state" property as stopped.

See Also:

Constant Field Values

STOPPING

public static final int STOPPING

Marks the "state" property as in-transition from ONLINE to OFFLINE.

See Also:

Constant Field Values

STARTING

public static final int STARTING

Marks the "state" property as in-transition from OFFLINE to ONLINE.

See Also:

Constant Field Values

Constructor Detail

DiscoveryMonitor

public DiscoveryMonitor()

Constructs a DiscoveryMonitor.

This constructor creates and initializes a multicast socket used to listen for DiscoveryResponder objects registering or unregistering. The default group (224.224.224.224) and port (9000) are used. No check is done on the default values: check will be performed by the start method.

DiscoveryMonitor

public DiscoveryMonitor(String multicastGroup,
                        int multicastPort)

Constructs a DiscoveryMonitor.

This constructor creates and initializes a multicast socket used to listen for DiscoveryResponder objects registering or unregistering. No check is done on the parameter values: check will be performed by the start method.

Parameters:

multicastGroup - The multicast group name.

multicastPort - The multicast port number.

DiscoveryMonitor

public DiscoveryMonitor(String multicastGroup,
                        int multicastPort,
                        InetAddress inf)

Constructs a DiscoveryMonitor.

This constructor creates and initializes a multicast socket used to listen for DiscoveryResponder objects registering or unregistering. No check is done on the parameter values: check will be performed by the start method.

Parameters:

multicastGroup - The multicast group name.

multicastPort - The multicast port number.

inf - The interface used by a MulticastSocket.

Since:

Java DMK 5.0

Method Detail

preRegister

public ObjectName preRegister(MBeanServer server,
                              ObjectName name)
                       throws Exception

Allows the MBean to perform any operations it needs before being registered in the MBean server. If the name of the MBean is not specified, the MBean can provide a name for its registration. If any exception is raised, the MBean will not be registered in the MBean server.

Specified by:

preRegister in interface MBeanRegistration

Parameters:

server - The MBean server in which the MBean will be registered.

name - The object name of the MBean.

Returns:

The name of the MBean registered.

Throws:

Exception - This exception should be caught by the MBean server and re-thrown as an MBeanRegistrationException.

postRegister

public void postRegister(Boolean registrationDone)

Allows the MBean to perform any operations needed after having been registered in the MBean server or after the registration has failed.

Specified by:

postRegister in interface MBeanRegistration

Parameters:

registrationDone - Indicates whether or not the MBean has been successfully registered in the MBean server. The value false means that the registration phase has failed.

preDeregister

public void preDeregister()
                   throws Exception

Allows the MBean to perform any operations it needs before being unregistered by the MBean server.

Specified by:

preDeregister in interface MBeanRegistration

Throws:

java.langException - This exception should be caught by the MBean server and re-thrown as an MBeanRegistrationException.

Exception

postDeregister

public void postDeregister()

Allows the MBean to perform any operations needed after having been unregistered in the MBean server.

Specified by:

postDeregister in interface MBeanRegistration

start

public void start()
           throws IOException

Starts listening for DiscoveryResponder objects registering/unregistering.

This method has no effect if the DiscoveryMonitor is ONLINE or STOPPING or STARTING.

Specified by:

start in interface DiscoveryMonitorMBean

Throws:

IOException - The creation of the Multicast socket failed.

stop

public void stop()

Stops this DiscoveryMonitor.

This method has no effect if the monitor is OFFLINE or STOPPING or STARTING.

Specified by:

stop in interface DiscoveryMonitorMBean

getState

public Integer getState()

Returns the state of this DiscoveryMonitor.

Specified by:

getState in interface DiscoveryMonitorMBean

Returns:

ONLINE,OFFLINE, STOPPING or STARTING.

getStateString

public String getStateString()

Returns the state of this DiscoveryMonitor in string form.

Specified by:

getStateString in interface DiscoveryMonitorMBean

Returns:

One of the strings "ONLINE", "OFFLINE", "STOPPING" or "STARTING".

getMulticastGroup

public String getMulticastGroup()

Returns the multicast group. A multicast group is specified by a class D IP address, those in the range 224.0.0.1 to 239.255.255.255.

Specified by:

getMulticastGroup in interface DiscoveryMonitorMBean

Returns:

A string containing the multicast group name.

setMulticastGroup

public void setMulticastGroup(String multicastGroup)
                       throws IllegalStateException

Sets the multicast group name. A multicast group is specified by a class D IP address, those in the range 224.0.0.1 to 239.255.255.255.

Only available if state in OFFLINE

Specified by:

setMulticastGroup in interface DiscoveryMonitorMBean

Parameters:

multicastGroup - The multicast group name.

Throws:

IllegalStateException - This method has been invoked while the DiscoveryMonitor was ONLINE or STARTING.

getMulticastPort

public int getMulticastPort()

Returns the multicast port. It can be any standard UDP port number.

Specified by:

getMulticastPort in interface DiscoveryMonitorMBean

Returns:

The multicast port number.

setMulticastPort

public void setMulticastPort(int multicastPort)
                      throws IllegalStateException

Sets the multicast port. It can be any standard UDP port number.

Only available if state in OFFLINE

Specified by:

setMulticastPort in interface DiscoveryMonitorMBean

Parameters:

multicastPort - The multicast port.

Throws:

IllegalStateException - This method has been invoked while the DiscoveryMonitor was ONLINE or STARTING.

waitState

public boolean waitState(int state,
                         long timeout)

Waits until either the State attribute of this MBean equals the specified state parameter, or the specified timeout has elapsed. The method waitState returns with a boolean value indicating whether the specified state parameter equals the value of this MBean's State attribute at the time the method terminates.

Two special cases for the timeout parameter value are:

• if timeout is negative then waitState returns immediately (i.e. does not wait at all),
• if timeout equals zero then waitState waits until the value of this MBean's State attribute is the same as the state parameter (i.e. will wait indefinitely if this condition is never met).

Specified by:

waitState in interface DiscoveryMonitorMBean

Parameters:

state - The value of this MBean's State attribute to wait for. state can be one of: DiscoveryMonitor.OFFLINE, DiscoveryMonitor.ONLINE, DiscoveryMonitor.STARTING, DiscoveryMonitor.STOPPING.

timeout - The maximum time to wait for, in milliseconds, if positive. Infinite time out if 0, or no waiting at all if negative.

Returns:

true if the value of this MBean's State attribute is the same as the state parameter; false otherwise.