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Class Timer

All Implemented Interfaces:
MBeanRegistration, NotificationBroadcaster, NotificationEmitter, TimerMBean 
public class Timer
extends NotificationBroadcasterSupport
implements TimerMBean, MBeanRegistration

Provides the implementation of the timer MBean. The timer MBean sends out an alarm at a specified time that wakes up all the listeners registered to receive timer notifications.

This class manages a list of dated timer notifications. A method allows users to add/remove as many notifications as required. When a timer notification is emitted by the timer and becomes obsolete, it is automatically removed from the list of timer notifications.
Additional timer notifications can be added into regularly repeating notifications.

Note:

  1. When sending timer notifications, the timer updates the notification sequence number irrespective of the notification type.
  2. The timer service relies on the system date of the host where the Timer class is loaded. Listeners may receive untimely notifications if their host has a different system date. To avoid such problems, synchronize the system date of all host machines where timing is needed.
  3. The default behavior for periodic notifications is fixed-delay execution, as specified in Timer. In order to use fixed-rate execution, use the overloaded addNotification(String, String, Object, Date, long, long, boolean) method.
  4. Notification listeners are potentially all executed in the same thread. Therefore, they should execute rapidly to avoid holding up other listeners or perturbing the regularity of fixed-delay executions. See NotificationBroadcasterSupport.
Since:
1.5

Fields

ONE_SECOND

public static final long ONE_SECOND

Number of milliseconds in one second. Useful constant for the addNotification method.

ONE_MINUTE

public static final long ONE_MINUTE

Number of milliseconds in one minute. Useful constant for the addNotification method.

ONE_HOUR

public static final long ONE_HOUR

Number of milliseconds in one hour. Useful constant for the addNotification method.

ONE_DAY

public static final long ONE_DAY

Number of milliseconds in one day. Useful constant for the addNotification method.

ONE_WEEK

public static final long ONE_WEEK

Number of milliseconds in one week. Useful constant for the addNotification method.

Constructors

Timer

public Timer()

Default constructor.

Methods

preRegister

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

Allows the timer MBean to perform any operations it needs before being registered in the MBean server.

Not used in this context.

Specified by:
preRegister in interface MBeanRegistration
Parameters:
server - The MBean server in which the timer MBean will be registered.
name - The object name of the timer MBean.
Returns:
The name of the timer MBean registered.
Throws:
Exception

postRegister

public void postRegister(Boolean registrationDone)

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

Not used in this context.

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

Stops the timer.

Specified by:
preDeregister in interface MBeanRegistration
Throws:
Exception

postDeregister

public void postDeregister()

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

Not used in this context.

Specified by:
postDeregister in interface MBeanRegistration

getNotificationInfo

public MBeanNotificationInfo[] getNotificationInfo()

Description copied from interface: NotificationBroadcaster

Returns an array indicating, for each notification this MBean may send, the name of the Java class of the notification and the notification type.

It is not illegal for the MBean to send notifications not described in this array. However, some clients of the MBean server may depend on the array being complete for their correct functioning.

Specified by:
getNotificationInfo in interface NotificationBroadcaster
Overrides:
getNotificationInfo in class NotificationBroadcasterSupport
Returns:
the array of possible notifications.

start

public void start()

Starts the timer.

If there is one or more timer notifications before the time in the list of notifications, the notification is sent according to the sendPastNotifications flag and then, updated according to its period and remaining number of occurrences. If the timer notification date remains earlier than the current date, this notification is just removed from the list of notifications.

Specified by:
start in interface TimerMBean

stop

public void stop()

Stops the timer.

Specified by:
stop in interface TimerMBean

addNotification

public Integer addNotification(String type,
                               String message,
                               Object userData,
                               Date date,
                               long period,
                               long nbOccurences,
                               boolean fixedRate)
                        throws IllegalArgumentException

Creates a new timer notification with the specified type, message and userData and inserts it into the list of notifications with a given date, period and number of occurrences.

If the timer notification to be inserted has a date that is before the current date, the method behaves as if the specified date were the current date.
For once-off notifications, the notification is delivered immediately.
For periodic notifications, the first notification is delivered immediately and the subsequent ones are spaced as specified by the period parameter.

Note that once the timer notification has been added into the list of notifications, its associated date, period and number of occurrences cannot be updated.

In the case of a periodic notification, the value of parameter fixedRate is used to specify the execution scheme, as specified in Timer.

Specified by:
addNotification in interface TimerMBean
Parameters:
type - The timer notification type.
message - The timer notification detailed message.
userData - The timer notification user data object.
date - The date when the notification occurs.
period - The period of the timer notification (in milliseconds).
nbOccurences - The total number the timer notification will be emitted.
fixedRate - If true and if the notification is periodic, the notification is scheduled with a fixed-rate execution scheme. If false and if the notification is periodic, the notification is scheduled with a fixed-delay execution scheme. Ignored if the notification is not periodic.
Returns:
The identifier of the new created timer notification.
Throws:
IllegalArgumentException - The date is null or the period or the number of occurrences is negative.
See Also:
addNotification(String, String, Object, Date, long, long)

addNotification

public Integer addNotification(String type,
                               String message,
                               Object userData,
                               Date date,
                               long period,
                               long nbOccurences)
                        throws IllegalArgumentException

Creates a new timer notification with the specified type, message and userData and inserts it into the list of notifications with a given date, period and number of occurrences.

If the timer notification to be inserted has a date that is before the current date, the method behaves as if the specified date were the current date.
For once-off notifications, the notification is delivered immediately.
For periodic notifications, the first notification is delivered immediately and the subsequent ones are spaced as specified by the period parameter.

Note that once the timer notification has been added into the list of notifications, its associated date, period and number of occurrences cannot be updated.

In the case of a periodic notification, uses a fixed-delay execution scheme, as specified in Timer. In order to use a fixed-rate execution scheme, use addNotification(String, String, Object, Date, long, long, boolean) instead.

Specified by:
addNotification in interface TimerMBean
Parameters:
type - The timer notification type.
message - The timer notification detailed message.
userData - The timer notification user data object.
date - The date when the notification occurs.
period - The period of the timer notification (in milliseconds).
nbOccurences - The total number the timer notification will be emitted.
Returns:
The identifier of the new created timer notification.
Throws:
IllegalArgumentException - The date is null or the period or the number of occurrences is negative.
See Also:
addNotification(String, String, Object, Date, long, long, boolean)

addNotification

public Integer addNotification(String type,
                               String message,
                               Object userData,
                               Date date,
                               long period)
                        throws IllegalArgumentException

Creates a new timer notification with the specified type, message and userData and inserts it into the list of notifications with a given date and period and a null number of occurrences.

The timer notification will repeat continuously using the timer period using a fixed-delay execution scheme, as specified in Timer. In order to use a fixed-rate execution scheme, use addNotification(String, String, Object, Date, long, long, boolean) instead.

If the timer notification to be inserted has a date that is before the current date, the method behaves as if the specified date were the current date. The first notification is delivered immediately and the subsequent ones are spaced as specified by the period parameter.

Specified by:
addNotification in interface TimerMBean
Parameters:
type - The timer notification type.
message - The timer notification detailed message.
userData - The timer notification user data object.
date - The date when the notification occurs.
period - The period of the timer notification (in milliseconds).
Returns:
The identifier of the new created timer notification.
Throws:
IllegalArgumentException - The date is null or the period is negative.

addNotification

public Integer addNotification(String type,
                               String message,
                               Object userData,
                               Date date)
                        throws IllegalArgumentException

Creates a new timer notification with the specified type, message and userData and inserts it into the list of notifications with a given date and a null period and number of occurrences.

The timer notification will be handled once at the specified date.

If the timer notification to be inserted has a date that is before the current date, the method behaves as if the specified date were the current date and the notification is delivered immediately.

Specified by:
addNotification in interface TimerMBean
Parameters:
type - The timer notification type.
message - The timer notification detailed message.
userData - The timer notification user data object.
date - The date when the notification occurs.
Returns:
The identifier of the new created timer notification.
Throws:
IllegalArgumentException - The date is null.

removeNotification

public void removeNotification(Integer id)
                        throws InstanceNotFoundException

Removes the timer notification corresponding to the specified identifier from the list of notifications.

Specified by:
removeNotification in interface TimerMBean
Parameters:
id - The timer notification identifier.
Throws:
InstanceNotFoundException - The specified identifier does not correspond to any timer notification in the list of notifications of this timer MBean.

removeNotifications

public void removeNotifications(String type)
                         throws InstanceNotFoundException

Removes all the timer notifications corresponding to the specified type from the list of notifications.

Specified by:
removeNotifications in interface TimerMBean
Parameters:
type - The timer notification type.
Throws:
InstanceNotFoundException - The specified type does not correspond to any timer notification in the list of notifications of this timer MBean.

removeAllNotifications

public void removeAllNotifications()

Removes all the timer notifications from the list of notifications and resets the counter used to update the timer notification identifiers.

Specified by:
removeAllNotifications in interface TimerMBean

getNbNotifications

public int getNbNotifications()

Gets the number of timer notifications registered into the list of notifications.

Specified by:
getNbNotifications in interface TimerMBean
Returns:
The number of timer notifications.

getAllNotificationIDs

public Vector<Integer> getAllNotificationIDs()

Gets all timer notification identifiers registered into the list of notifications.

Specified by:
getAllNotificationIDs in interface TimerMBean
Returns:
A vector of Integer objects containing all the timer notification identifiers.
The vector is empty if there is no timer notification registered for this timer MBean.

getNotificationIDs

public Vector<Integer> getNotificationIDs(String type)

Gets all the identifiers of timer notifications corresponding to the specified type.

Specified by:
getNotificationIDs in interface TimerMBean
Parameters:
type - The timer notification type.
Returns:
A vector of Integer objects containing all the identifiers of timer notifications with the specified type.
The vector is empty if there is no timer notifications registered for this timer MBean with the specified type.

getNotificationType

public String getNotificationType(Integer id)

Gets the timer notification type corresponding to the specified identifier.

Specified by:
getNotificationType in interface TimerMBean
Parameters:
id - The timer notification identifier.
Returns:
The timer notification type or null if the identifier is not mapped to any timer notification registered for this timer MBean.

getNotificationMessage

public String getNotificationMessage(Integer id)

Gets the timer notification detailed message corresponding to the specified identifier.

Specified by:
getNotificationMessage in interface TimerMBean
Parameters:
id - The timer notification identifier.
Returns:
The timer notification detailed message or null if the identifier is not mapped to any timer notification registered for this timer MBean.

getNotificationUserData

public Object getNotificationUserData(Integer id)

Gets the timer notification user data object corresponding to the specified identifier.

Specified by:
getNotificationUserData in interface TimerMBean
Parameters:
id - The timer notification identifier.
Returns:
The timer notification user data object or null if the identifier is not mapped to any timer notification registered for this timer MBean.

getDate

public Date getDate(Integer id)

Gets a copy of the date associated to a timer notification.

Specified by:
getDate in interface TimerMBean
Parameters:
id - The timer notification identifier.
Returns:
A copy of the date or null if the identifier is not mapped to any timer notification registered for this timer MBean.

getPeriod

public Long getPeriod(Integer id)

Gets a copy of the period (in milliseconds) associated to a timer notification.

Specified by:
getPeriod in interface TimerMBean
Parameters:
id - The timer notification identifier.
Returns:
A copy of the period or null if the identifier is not mapped to any timer notification registered for this timer MBean.

getNbOccurences

public Long getNbOccurences(Integer id)

Gets a copy of the remaining number of occurrences associated to a timer notification.

Specified by:
getNbOccurences in interface TimerMBean
Parameters:
id - The timer notification identifier.
Returns:
A copy of the remaining number of occurrences or null if the identifier is not mapped to any timer notification registered for this timer MBean.

getFixedRate

public Boolean getFixedRate(Integer id)

Gets a copy of the flag indicating whether a periodic notification is executed at fixed-delay or at fixed-rate.

Specified by:
getFixedRate in interface TimerMBean
Parameters:
id - The timer notification identifier.
Returns:
A copy of the flag indicating whether a periodic notification is executed at fixed-delay or at fixed-rate.

getSendPastNotifications

public boolean getSendPastNotifications()

Gets the flag indicating whether or not the timer sends past notifications.
The default value of the past notifications sending on/off flag is false.

Specified by:
getSendPastNotifications in interface TimerMBean
Returns:
The past notifications sending on/off flag value.
See Also:
setSendPastNotifications(boolean)

setSendPastNotifications

public void setSendPastNotifications(boolean value)

Sets the flag indicating whether the timer sends past notifications or not.
The default value of the past notifications sending on/off flag is false.

Specified by:
setSendPastNotifications in interface TimerMBean
Parameters:
value - The past notifications sending on/off flag value.
See Also:
getSendPastNotifications()

isActive

public boolean isActive()

Tests whether the timer MBean is active. A timer MBean is marked active when the start method is called. It becomes inactive when the stop method is called.
The default value of the active on/off flag is false.

Specified by:
isActive in interface TimerMBean
Returns:
true if the timer MBean is active, false otherwise.

isEmpty

public boolean isEmpty()

Tests whether the list of timer notifications is empty.

Specified by:
isEmpty in interface TimerMBean
Returns:
true if the list of timer notifications is empty, false otherwise.

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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