org.dlese.dpc.schemedit

Class SessionRegistry

java.lang.Object

org.dlese.dpc.schemedit.SessionRegistry

All Implemented Interfaces:

java.util.EventListener, javax.servlet.http.HttpSessionListener, javax.servlet.ServletContextListener

public class SessionRegistry
extends java.lang.Object
implements javax.servlet.ServletContextListener, javax.servlet.http.HttpSessionListener

Maintains a registry of sessions and also manages record locking.

As ServletContextListener, receives "contextInitialized" event, and sets servletContext attribute.

As HttpSessionListener, receives "sessionCreated" and "sessionDestroyed" events. SessionBeans are created when the session is created, and destroyed when the session is destroyed.

Author:

ostwald

Constructor Summary

Constructors

Constructor and Description
SessionRegistry() Constructor for the SessionRegistry object.

Method Summary

Modifier and Type	Method and Description
void	contextDestroyed(javax.servlet.ServletContextEvent event) Method called when a context is destroyed.
void	contextInitialized(javax.servlet.ServletContextEvent event) Called when context is initialized, sets ServletContext as class attribute.
void	destroy() Release locked records
boolean	getLock(java.lang.String recId, java.lang.String sessionId) Gets the lock attribute of the SessionRegistry object.
java.util.Map	getLockedRecords() Gets the lockedRecords attribute of the SessionRegistry object, which stores all locked records and the sessions that owns the lock.
javax.servlet.http.HttpSession	getSession(java.lang.String id) Returns active session corresponding to given Id.
SessionBean	getSessionBean(javax.servlet.http.HttpServletRequest request) Return the SessionBean associated with the HttpSession for the provided request.
java.util.List	getSessionBeans() Returns a list of all active SessionBean instances.
boolean	getUniqueLock(java.lang.String recId, java.lang.String sessionId) A version of getLock that only allows a single record to be locked by a single session at a time
java.util.List	getUserSessionBeans(User user)
boolean	isLocked(java.lang.String recId) Returns true if there is a lock for the given record.
java.util.List	myLockedRecords(java.lang.String sessionId) Find records locked by a given session.
boolean	ownsLock(java.lang.String recId, java.lang.String sessionId) Is a record locked by the given session?
void	registerSessionBean(SessionBean sessionBean) Register a sessionBean by putting it into the sessionBeanMap.
void	releaseAllLocks() Release all locked records.
void	releaseAllLocks(java.lang.String sessionId) Release all the locks owned by a particluar session.
boolean	releaseLock(java.lang.String recId) Releases the lock for given record, regardless of what session owns the lock.
boolean	releaseLock(java.lang.String recId, java.lang.String sessionId) Release lock held by specified sesssion
void	sessionCreated(javax.servlet.http.HttpSessionEvent se) Called when a session is created with sole effect of putting the created session into the activeSessions map.
void	sessionDestroyed(javax.servlet.http.HttpSessionEvent se) Notified when a session is about to be destroyed - removes the session from the activeSessions map and unregisteres sessionBean.
void	unregisterSessionBean(java.lang.String sessionId) Unregister a sessionBean by calling its destroy method (releasing all held locks), and removing its entry from the sessionBeanMap.

Methods inherited from class java.lang.Object

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

Constructor Detail

SessionRegistry

public SessionRegistry()

Constructor for the SessionRegistry object.

activeSessionsMap map maintains the set of ALL active sessions, and is only modified by sessionCreated(HttpSessionEvent) and sessionDestroyed(HttpSessionEvent) listeners.

sessionBeanMap maintains the set of sessionBean instances, which are created only for interactive sessions - which excludes sessions created by webservice requests.

Method Detail

contextDestroyed

public void contextDestroyed(javax.servlet.ServletContextEvent event)

Method called when a context is destroyed. Unregisters all sessions and empties lockedRecords.

Specified by:

contextDestroyed in interface javax.servlet.ServletContextListener

Parameters:

event - Description of the Parameter

See Also:

unregisterSessionBean(String)

contextInitialized

public void contextInitialized(javax.servlet.ServletContextEvent event)

Called when context is initialized, sets ServletContext as class attribute.

Specified by:

contextInitialized in interface javax.servlet.ServletContextListener

Parameters:

event - Description of the Parameter

getLockedRecords

public java.util.Map getLockedRecords()

Gets the lockedRecords attribute of the SessionRegistry object, which stores all locked records and the sessions that owns the lock.

Returns:

The lockedRecords value

sessionCreated

public void sessionCreated(javax.servlet.http.HttpSessionEvent se)

Called when a session is created with sole effect of putting the created session into the activeSessions map. Items are removed from the activeSessionsMap wehn sessions are destroyed.

Specified by:

sessionCreated in interface javax.servlet.http.HttpSessionListener

Parameters:

se - notification event

sessionDestroyed

public void sessionDestroyed(javax.servlet.http.HttpSessionEvent se)

Notified when a session is about to be destroyed - removes the session from the activeSessions map and unregisteres sessionBean.

Specified by:

sessionDestroyed in interface javax.servlet.http.HttpSessionListener

Parameters:

se - notification event

See Also:

unregisterSessionBean(String)

isLocked

public boolean isLocked(java.lang.String recId)

Returns true if there is a lock for the given record.

Parameters:

recId - Description of the Parameter

Returns:

The locked value

ownsLock

public boolean ownsLock(java.lang.String recId,
                        java.lang.String sessionId)

Is a record locked by the given session?

Parameters:

recId - Description of the Parameter

sessionId - Id of given session

Returns:

true if session owns lock to record

myLockedRecords

public java.util.List myLockedRecords(java.lang.String sessionId)

Find records locked by a given session. Should never be more than one!

Parameters:

sessionId - Description of the Parameter

Returns:

list of record Ids

releaseAllLocks

public void releaseAllLocks()

Release all locked records.

releaseAllLocks

public void releaseAllLocks(java.lang.String sessionId)

Release all the locks owned by a particluar session.

Parameters:

sessionId - Id of session that is releasing records.

getLock

public boolean getLock(java.lang.String recId,
                       java.lang.String sessionId)

Gets the lock attribute of the SessionRegistry object.

Parameters:

recId - Description of the Parameter

sessionId - Description of the Parameter

Returns:

true if lock is obtained by requesting session

getUniqueLock

public boolean getUniqueLock(java.lang.String recId,
                             java.lang.String sessionId)

A version of getLock that only allows a single record to be locked by a single session at a time

Parameters:

recId - Description of the Parameter

sessionId - Description of the Parameter

Returns:

The uniqueLock value

releaseLock

public boolean releaseLock(java.lang.String recId)

Releases the lock for given record, regardless of what session owns the lock.

Parameters:

recId - Description of the Parameter

Returns:

true if there was a lock for given record ID

releaseLock

public boolean releaseLock(java.lang.String recId,
                           java.lang.String sessionId)

Release lock held by specified sesssion

Parameters:

recId - Description of the Parameter

sessionId - Description of the Parameter

Returns:

true if specified session owned lock on record

registerSessionBean

public void registerSessionBean(SessionBean sessionBean)

Register a sessionBean by putting it into the sessionBeanMap.

Parameters:

sessionBean - Description of the Parameter

unregisterSessionBean

public void unregisterSessionBean(java.lang.String sessionId)

Unregister a sessionBean by calling its destroy method (releasing all held locks), and removing its entry from the sessionBeanMap.

Parameters:

sessionId - Description of the Parameter

getSession

public javax.servlet.http.HttpSession getSession(java.lang.String id)

Returns active session corresponding to given Id.

Parameters:

id - session id

Returns:

a HttpSession instance, or null if none was found for given id.

getSessionBean

public SessionBean getSessionBean(javax.servlet.http.HttpServletRequest request)

Return the SessionBean associated with the HttpSession for the provided request.

If a sessionBean does not yet exist for a valid session, then it is created and bound to the session context. This method is the standard way of obtaining of obtaining a sessionBean from within a Controller or FormBean.

Parameters:

request - A request instance that is associated with a session

Returns:

The sessionBean value for the request's session.

getUserSessionBeans

public java.util.List getUserSessionBeans(User user)

getSessionBeans

public java.util.List getSessionBeans()

Returns a list of all active SessionBean instances.

Unregisters sessionBeans corresponding to sessions that have been invalidated.

Returns:

list of SessionBean

destroy

public void destroy()

Release locked records