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## org.apache.catalina.session
Class PersistentManagerBase

    java.lang.Object
      |
      +--org.apache.catalina.session.ManagerBase
            |
            +--org.apache.catalina.session.PersistentManagerBase

All Implemented Interfaces:
  java.util.EventListener, Lifecycle, Manager, java.beans.PropertyChangeListener, java.lang.Runnable

Direct Known Subclasses:
  DistributedManager, PersistentManager

public abstract class PersistentManagerBase
extends ManagerBase
implements Lifecycle, java.beans.PropertyChangeListener, java.lang.Runnable

Extends the ManagerBase class to implement most of the functionality required by a Manager which supports any kind of persistence, even if onlyfor restarts.

IMPLEMENTATION NOTE: Correct behavior of session storing and reloading depends upon external calls to the `start()` and `stop()` methods of this class at the correct times.

Version:
  $Revision: 1.6 $ $Date: 2001/08/10 20:12:00 $
Author:
  Craig R. McClanahan

Field Summary
`protected LifecycleSupport` | `lifecycle` The lifecycle event support for this component.
`protected static java.lang.String` | `name` The descriptive name of this Manager implementation (for logging).
`protected boolean` | `threadDone` The background thread completion semaphore.

Fields inherited from class org.apache.catalina.session.ManagerBase
`algorithm, container, debug, DEFAULT_ALGORITHM, digest, distributable, entropy, maxInactiveInterval, random, randomClass, recycled, SESSION_ID_BYTES, sessions, sm, support`

Fields inherited from interface org.apache.catalina.Lifecycle
`START_EVENT, STOP_EVENT`

Constructor Summary
`PersistentManagerBase()`

Method Summary
`void` | `addLifecycleListener(LifecycleListener listener)` Add a lifecycle event listener to this component.
`void` | `clearStore()` Clear all sessions from the Store.
`Session` | `createSession()` Return a new session object as long as the number of active sessions does not exceed maxActiveSessions.
`Session` | `findSession(java.lang.String id)` Return the active Session, associated with this Manager, with the specified session id (if any); otherwise return `null`.
`int` | `getCheckInterval()` Return the check interval (in seconds) for this Manager.
`java.lang.String` | `getInfo()` Return descriptive information about this Manager implementation and the corresponding version number, in the format `<description>/<version>`.
`int` | `getMaxActiveSessions()` Return the maximum number of active Sessions allowed, or -1 for no limit.
`int` | `getMaxIdleBackup()` Indicates how many seconds old a session can get, after its last use in a request, before it should be backed up to the store.
`int` | `getMaxIdleSwap()` The time in seconds after which a session should be swapped out of memory to disk.
`int` | `getMinIdleSwap()` The minimum time in seconds that a session must be idle before it can be swapped out of memory, or -1 if it can be swapped out at any time.
`java.lang.String` | `getName()` Return the descriptive short name of this Manager implementation.
`boolean` | `getSaveOnRestart()` Indicates whether sessions are saved when the Manager is shut down properly.
`Store` | `getStore()` Return the Store object which manages persistent Session storage for this Manager.
`protected boolean` | `isSessionStale(Session session, long timeNow)` Indicate whether the session has been idle for longer than its expiration date as of the supplied time.
`protected boolean` | `isStarted()` Get the started status.
`void` | `load()` Load all sessions found in the persistence mechanism, assuming they are marked as valid and have not passed their expiration limit.
`protected void` | `processExpires()` Invalidate all sessions that have expired.
`protected void` | `processMaxActiveSwaps()` Swap idle sessions out to Store if too many are active
`protected void` | `processMaxIdleBackups()` Back up idle sessions.
`protected void` | `processMaxIdleSwaps()` Swap idle sessions out to Store if they are idle too long.
`void` | `processPersistenceChecks()` Called by the background thread after active sessions have been checked for expiration, to allow sessions to be swapped out, backed up, etc.
`void` | `propertyChange(java.beans.PropertyChangeEvent event)` Process property change events from our associated Context.
`void` | `remove(Session session)` Remove this Session from the active Sessions for this Manager, and from the Store.
`void` | `removeLifecycleListener(LifecycleListener listener)` Remove a lifecycle event listener from this component.
`void` | `run()` The background thread that checks for session timeouts and shutdown.
`void` | `setCheckInterval(int checkInterval)` Set the check interval (in seconds) for this Manager.
`void` | `setContainer(Container container)` Set the Container with which this Manager has been associated.
`void` | `setMaxActiveSessions(int max)` Set the maximum number of actives Sessions allowed, or -1 for no limit.
`void` | `setMaxIdleBackup(int backup)` Sets the option to back sessions up to the Store after they are used in a request.
`void` | `setMaxIdleSwap(int max)` Sets the time in seconds after which a session should be swapped out of memory to disk.
`void` | `setMinIdleSwap(int min)` Sets the minimum time in seconds that a session must be idle before it can be swapped out of memory due to maxActiveSession.
`void` | `setSaveOnRestart(boolean saveOnRestart)` Set the option to save sessions to the Store when the Manager is shut down, then loaded when the Manager starts again.
`protected void` | `setStarted(boolean started)` Set the started flag
`void` | `setStore(Store store)` Set the Store object which will manage persistent Session storage for this Manager.
`void` | `start()` Prepare for the beginning of active use of the public methods of this component.
`void` | `stop()` Gracefully terminate the active use of the public methods of this component.
`protected Session` | `swapIn(java.lang.String id)` Look for a session in the Store and, if found, restore it in the Manager's list of active sessions if appropriate.
`protected void` | `swapOut(Session session)` Remove the session from the Manager's list of active sessions and write it out to the Store.
`protected void` | `threadSleep()` Sleep for the duration specified by the `checkInterval` property.
`protected void` | `threadStart()` Start the background thread that will periodically check for session timeouts.
`protected void` | `threadStop()` Stop the background thread that is periodically checking for session timeouts.
`void` | `unload()` Save all currently active sessions in the appropriate persistence mechanism, if any.
`protected void` | `writeSession(Session session)` Write the provided session to the Store without modifying the copy in memory or triggering passivation events.

Methods inherited from class org.apache.catalina.session.ManagerBase
`add, addPropertyChangeListener, findSessions, generateSessionId, getAlgorithm, getContainer, getDebug, getDigest, getDistributable, getEntropy, getMaxInactiveInterval, getRandom, getRandomClass, removePropertyChangeListener, setAlgorithm, setDebug, setDistributable, setEntropy, setMaxInactiveInterval, setRandomClass`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### lifecycle

    protected LifecycleSupport lifecycle

  The lifecycle event support for this component.

### name

    protected static java.lang.String name

  The descriptive name of this Manager implementation (for logging).

### threadDone

    protected boolean threadDone

  The background thread completion semaphore.

Constructor Detail

### PersistentManagerBase

    public PersistentManagerBase()

Method Detail

### getCheckInterval

    public int getCheckInterval()

  Return the check interval (in seconds) for this Manager.

### setCheckInterval

    public void setCheckInterval(int checkInterval)

  Set the check interval (in seconds) for this Manager.
  Parameters:
    `checkInterval` - The new check interval

### getMaxIdleBackup

    public int getMaxIdleBackup()

  Indicates how many seconds old a session can get, after its last use in a request, before it should be backed up to the store. -1 means sessions are not backed up.

### setMaxIdleBackup

    public void setMaxIdleBackup(int backup)

  Sets the option to back sessions up to the Store after they are used in a request. Sessions remain available in memory after being backed up, so they are not passivated as they are when swapped out. The value set indicates how old a session may get (since its last use) before it must be backed up: -1 means sessions are not backed up.

  Note that this is not a hard limit: sessions are checked against this age limit periodically according to checkInterval. This value should be considered to indicate when a session is ripe for backing up.

  So it is possible that a session may be idle for maxIdleBackup + checkInterval seconds, plus the time it takes to handle other session expiration, swapping, etc. tasks.

  Parameters:
    `backup` - The number of seconds after their last accessed time when they should be written to the Store.

### getMaxIdleSwap

    public int getMaxIdleSwap()

  The time in seconds after which a session should be swapped out of memory to disk.

### setMaxIdleSwap

    public void setMaxIdleSwap(int max)

  Sets the time in seconds after which a session should be swapped out of memory to disk.

### getMinIdleSwap

    public int getMinIdleSwap()

  The minimum time in seconds that a session must be idle before it can be swapped out of memory, or -1 if it can be swapped out at any time.

### setMinIdleSwap

    public void setMinIdleSwap(int min)

  Sets the minimum time in seconds that a session must be idle before it can be swapped out of memory due to maxActiveSession. Set it to -1 if it can be swapped out at any time.

### setContainer

    public void setContainer(Container container)

  Set the Container with which this Manager has been associated. If it is a Context (the usual case), listen for changes to the session timeout property.
  Overrides:
    `setContainer` in class `ManagerBase`
  Parameters:
    `container` - The associated Container

### getInfo

    public java.lang.String getInfo()

  Return descriptive information about this Manager implementation and the corresponding version number, in the format `<description>/<version>`.
  Overrides:
    `getInfo` in class `ManagerBase`

### getMaxActiveSessions

    public int getMaxActiveSessions()

  Return the maximum number of active Sessions allowed, or -1 for no limit.

### setMaxActiveSessions

    public void setMaxActiveSessions(int max)

  Set the maximum number of actives Sessions allowed, or -1 for no limit.
  Parameters:
    `max` - The new maximum number of sessions

### getName

    public java.lang.String getName()

  Return the descriptive short name of this Manager implementation.
  Overrides:
    `getName` in class `ManagerBase`

### isStarted

    protected boolean isStarted()

  Get the started status.

### setStarted

    protected void setStarted(boolean started)

  Set the started flag

### setStore

    public void setStore(Store store)

  Set the Store object which will manage persistent Session storage for this Manager.
  Parameters:
    `store` - the associated Store

### getStore

    public Store getStore()

  Return the Store object which manages persistent Session storage for this Manager.

### getSaveOnRestart

    public boolean getSaveOnRestart()

  Indicates whether sessions are saved when the Manager is shut down properly. This requires the unload() method to be called.

### setSaveOnRestart

    public void setSaveOnRestart(boolean saveOnRestart)

  Set the option to save sessions to the Store when the Manager is shut down, then loaded when the Manager starts again. If set to false, any sessions found in the Store may still be picked up when the Manager is started again.
  Parameters:
    `save` - true if sessions should be saved on restart, false if they should be ignored.

### clearStore

    public void clearStore()

  Clear all sessions from the Store.

### processPersistenceChecks

    public void processPersistenceChecks()

  Called by the background thread after active sessions have been checked for expiration, to allow sessions to be swapped out, backed up, etc.

### createSession

    public Session createSession()

  Return a new session object as long as the number of active sessions does not exceed maxActiveSessions. If there aren't too many active sessions, or if there is no limit, a session is created or retrieved from the recycled pool.
  Overrides:
    `createSession` in class `ManagerBase`
  Throws:
    `java.lang.IllegalStateException` - if a new session cannot be instantiated for any reason

### findSession

    public Session findSession(java.lang.String id)
                        throws java.io.IOException

  Return the active Session, associated with this Manager, with the specified session id (if any); otherwise return `null`. This method checks the persistence store if persistence is enabled, otherwise just uses the functionality from ManagerBase.
  Overrides:
    `findSession` in class `ManagerBase`
  Parameters:
    `id` - The session id for the session to be returned
  Throws:
    `java.lang.IllegalStateException` - if a new session cannot be instantiated for any reason
    `java.io.IOException` - if an input/output error occurs while processing this request

### load

    public void load()

  Load all sessions found in the persistence mechanism, assuming they are marked as valid and have not passed their expiration limit. If persistence is not supported, this method returns without doing anything.

  Note that by default, this method is not called by the MiddleManager class. In order to use it, a subclass must specifically call it, for example in the start() and/or processPersistenceChecks() methods.

  Following copied from interface: `org.apache.catalina.Manager`
  Throws:
    `java.lang.ClassNotFoundException` - if a serialized class cannot be found during the reload
    `java.io.IOException` - if an input/output error occurs

### remove

    public void remove(Session session)

  Remove this Session from the active Sessions for this Manager, and from the Store.
  Overrides:
    `remove` in class `ManagerBase`
  Parameters:
    `session` - Session to be removed

### unload

    public void unload()

  Save all currently active sessions in the appropriate persistence mechanism, if any. If persistence is not supported, this method returns without doing anything.

  Note that by default, this method is not called by the MiddleManager class. In order to use it, a subclass must specifically call it, for example in the stop() and/or processPersistenceChecks() methods.

  Following copied from interface: `org.apache.catalina.Manager`
  Throws:
    `java.io.IOException` - if an input/output error occurs

### swapIn

    protected Session swapIn(java.lang.String id)
                      throws java.io.IOException

  Look for a session in the Store and, if found, restore it in the Manager's list of active sessions if appropriate. The session will be removed from the Store after swapping in, but will not be added to the active session list if it is invalid or past its expiration.

### swapOut

    protected void swapOut(Session session)
                    throws java.io.IOException

  Remove the session from the Manager's list of active sessions and write it out to the Store. If the session is past its expiration or invalid, this method does nothing.
  Parameters:
    `session` - The Session to write out.

### writeSession

    protected void writeSession(Session session)
                         throws java.io.IOException

  Write the provided session to the Store without modifying the copy in memory or triggering passivation events. Does nothing if the session is invalid or past its expiration.

### addLifecycleListener

    public void addLifecycleListener(LifecycleListener listener)

  Add a lifecycle event listener to this component.
  Specified by:
    `addLifecycleListener` in interface `Lifecycle`
  Parameters:
    `listener` - The listener to add

### removeLifecycleListener

    public void removeLifecycleListener(LifecycleListener listener)

  Remove a lifecycle event listener from this component.
  Specified by:
    `removeLifecycleListener` in interface `Lifecycle`
  Parameters:
    `listener` - The listener to remove

### start

    public void start()
               throws LifecycleException

  Prepare for the beginning of active use of the public methods of this component. This method should be called after `configure()`, and before any of the public methods of the component are utilized.
  Specified by:
    `start` in interface `Lifecycle`
  Throws:
    `java.lang.IllegalStateException` - if this component has already been started
    `LifecycleException` - if this component detects a fatal error that prevents this component from being used

### stop

    public void stop()
              throws LifecycleException

  Gracefully terminate the active use of the public methods of this component. This method should be the last one called on a given instance of this component.
  Specified by:
    `stop` in interface `Lifecycle`
  Throws:
    `java.lang.IllegalStateException` - if this component has not been started
    `LifecycleException` - if this component detects a fatal error that needs to be reported

### propertyChange

    public void propertyChange(java.beans.PropertyChangeEvent event)

  Process property change events from our associated Context.
  Specified by:
    `propertyChange` in interface `java.beans.PropertyChangeListener`
  Parameters:
    `event` - The property change event that has occurred

### isSessionStale

    protected boolean isSessionStale(Session session,
                                     long timeNow)

  Indicate whether the session has been idle for longer than its expiration date as of the supplied time. FIXME: Probably belongs in the Session class.

### processExpires

    protected void processExpires()

  Invalidate all sessions that have expired.

### processMaxIdleSwaps

    protected void processMaxIdleSwaps()

  Swap idle sessions out to Store if they are idle too long.

### processMaxActiveSwaps

    protected void processMaxActiveSwaps()

  Swap idle sessions out to Store if too many are active

### processMaxIdleBackups

    protected void processMaxIdleBackups()

  Back up idle sessions.

### threadSleep

    protected void threadSleep()

  Sleep for the duration specified by the `checkInterval` property.

### threadStart

    protected void threadStart()

  Start the background thread that will periodically check for session timeouts.

### threadStop

    protected void threadStop()

  Stop the background thread that is periodically checking for session timeouts.

### run

    public void run()

  The background thread that checks for session timeouts and shutdown.
  Specified by:
    `run` in interface `java.lang.Runnable`

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