https://tomcat.apache.org/: Tomcat Servlet Engine Core Classes and Standard implementations 
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package org.apache.catalina;

import java.beans.PropertyChangeListener;
import java.io.IOException;


A Manager manages the pool of Sessions that are associated with a
particular Context. Different Manager implementations may support
value-added features such as the persistent storage of session data,
as well as migrating sessions for distributable web applications.


In order for a Manager implementation to successfully operate
with a Context implementation that implements reloading, it
must obey the following constraints:

    

  • Must implement Lifecycle so that the Context can indicate
    that a restart is required.

  • Must allow a call to stop() to be followed by a call to
    start() on the same Manager instance.



Author:Craig R. McClanahan
/**
 * A <b>Manager</b> manages the pool of Sessions that are associated with a
 * particular Context. Different Manager implementations may support
 * value-added features such as the persistent storage of session data,
 * as well as migrating sessions for distributable web applications.
 * <p>
 * In order for a <code>Manager</code> implementation to successfully operate
 * with a <code>Context</code> implementation that implements reloading, it
 * must obey the following constraints:
 * <ul>
 * <li>Must implement <code>Lifecycle</code> so that the Context can indicate
 *     that a restart is required.
 * <li>Must allow a call to <code>stop()</code> to be followed by a call to
 *     <code>start()</code> on the same <code>Manager</code> instance.
 * </ul>
 *
 * @author Craig R. McClanahan
 */
public interface Manager {

    // ------------------------------------------------------------- Properties

    
Get the Context with which this Manager is associated.

Returns:The associated Context
/**
     * Get the Context with which this Manager is associated.
     *
     * @return The associated Context
     */
    public Context getContext();


    
Set the Context with which this Manager is associated. The Context must be set to a non-null value before the Manager is first used. Multiple calls to this method before first use are permitted. Once the Manager has been used, this method may not be used to change the Context (including setting a null value) that the Manager is associated with. 
Params:
  • context – The newly associated Context
/**
     * Set the Context with which this Manager is associated. The Context must
     * be set to a non-null value before the Manager is first used. Multiple
     * calls to this method before first use are permitted. Once the Manager has
     * been used, this method may not be used to change the Context (including
     * setting a {@code null} value) that the Manager is associated with.
     *
     * @param context The newly associated Context
     */
    public void setContext(Context context);


    
Returns:the session id generator
/**
     * @return the session id generator
     */
    public SessionIdGenerator getSessionIdGenerator();


    
Sets the session id generator

Params:
  • sessionIdGenerator – The session id generator
/**
     * Sets the session id generator
     *
     * @param sessionIdGenerator The session id generator
     */
    public void setSessionIdGenerator(SessionIdGenerator sessionIdGenerator);


    
Returns the total number of sessions created by this manager.

Returns:Total number of sessions created by this manager.
/**
     * Returns the total number of sessions created by this manager.
     *
     * @return Total number of sessions created by this manager.
     */
    public long getSessionCounter();


    
Sets the total number of sessions created by this manager.

Params:
  • sessionCounter – Total number of sessions created by this manager.
/**
     * Sets the total number of sessions created by this manager.
     *
     * @param sessionCounter Total number of sessions created by this manager.
     */
    public void setSessionCounter(long sessionCounter);


    
Gets the maximum number of sessions that have been active at the same
time.

Returns:Maximum number of sessions that have been active at the same
time
/**
     * Gets the maximum number of sessions that have been active at the same
     * time.
     *
     * @return Maximum number of sessions that have been active at the same
     * time
     */
    public int getMaxActive();


    
(Re)sets the maximum number of sessions that have been active at the
same time.

Params:
  • maxActive – Maximum number of sessions that have been active at
the same time.
/**
     * (Re)sets the maximum number of sessions that have been active at the
     * same time.
     *
     * @param maxActive Maximum number of sessions that have been active at
     * the same time.
     */
    public void setMaxActive(int maxActive);


    
Gets the number of currently active sessions.

Returns:Number of currently active sessions
/**
     * Gets the number of currently active sessions.
     *
     * @return Number of currently active sessions
     */
    public int getActiveSessions();


    
Gets the number of sessions that have expired.

Returns:Number of sessions that have expired
/**
     * Gets the number of sessions that have expired.
     *
     * @return Number of sessions that have expired
     */
    public long getExpiredSessions();


    
Sets the number of sessions that have expired.

Params:
  • expiredSessions – Number of sessions that have expired
/**
     * Sets the number of sessions that have expired.
     *
     * @param expiredSessions Number of sessions that have expired
     */
    public void setExpiredSessions(long expiredSessions);


    
Gets the number of sessions that were not created because the maximum
number of active sessions was reached.

Returns:Number of rejected sessions
/**
     * Gets the number of sessions that were not created because the maximum
     * number of active sessions was reached.
     *
     * @return Number of rejected sessions
     */
    public int getRejectedSessions();


    
Gets the longest time (in seconds) that an expired session had been
alive.

Returns:Longest time (in seconds) that an expired session had been
alive.
/**
     * Gets the longest time (in seconds) that an expired session had been
     * alive.
     *
     * @return Longest time (in seconds) that an expired session had been
     * alive.
     */
    public int getSessionMaxAliveTime();


    
Sets the longest time (in seconds) that an expired session had been
alive.

Params:
  • sessionMaxAliveTime – Longest time (in seconds) that an expired
session had been alive.
/**
     * Sets the longest time (in seconds) that an expired session had been
     * alive.
     *
     * @param sessionMaxAliveTime Longest time (in seconds) that an expired
     * session had been alive.
     */
    public void setSessionMaxAliveTime(int sessionMaxAliveTime);


    
Gets the average time (in seconds) that expired sessions had been
alive. This may be based on sample data.

Returns:Average time (in seconds) that expired sessions had been
alive.
/**
     * Gets the average time (in seconds) that expired sessions had been
     * alive. This may be based on sample data.
     *
     * @return Average time (in seconds) that expired sessions had been
     * alive.
     */
    public int getSessionAverageAliveTime();


    
Gets the current rate of session creation (in session per minute). This
may be based on sample data.

Returns: The current rate (in sessions per minute) of session creation
/**
     * Gets the current rate of session creation (in session per minute). This
     * may be based on sample data.
     *
     * @return  The current rate (in sessions per minute) of session creation
     */
    public int getSessionCreateRate();


    
Gets the current rate of session expiration (in session per minute). This
may be based on sample data

Returns: The current rate (in sessions per minute) of session expiration
/**
     * Gets the current rate of session expiration (in session per minute). This
     * may be based on sample data
     *
     * @return  The current rate (in sessions per minute) of session expiration
     */
    public int getSessionExpireRate();


    // --------------------------------------------------------- Public Methods

    
Add this Session to the set of active Sessions for this Manager.

Params:
  • session – Session to be added
/**
     * Add this Session to the set of active Sessions for this Manager.
     *
     * @param session Session to be added
     */
    public void add(Session session);


    
Add a property change listener to this component.

Params:
  • listener – The listener to add
/**
     * Add a property change listener to this component.
     *
     * @param listener The listener to add
     */
    public void addPropertyChangeListener(PropertyChangeListener listener);


    
Change the session ID of the current session to a new randomly generated
session ID.

Params:
  • session –   The session to change the session ID for
/**
     * Change the session ID of the current session to a new randomly generated
     * session ID.
     *
     * @param session   The session to change the session ID for
     */
    public void changeSessionId(Session session);


    
Change the session ID of the current session to a specified session ID.

Params:
  • session –   The session to change the session ID for
  • newId –   new session ID
/**
     * Change the session ID of the current session to a specified session ID.
     *
     * @param session   The session to change the session ID for
     * @param newId   new session ID
     */
    public void changeSessionId(Session session, String newId);


    
Get a session from the recycled ones or create a new empty one.
The PersistentManager manager does not need to create session data
because it reads it from the Store.

Returns:An empty Session object
/**
     * Get a session from the recycled ones or create a new empty one.
     * The PersistentManager manager does not need to create session data
     * because it reads it from the Store.
     *
     * @return An empty Session object
     */
    public Session createEmptySession();


    
Construct and return a new session object, based on the default
settings specified by this Manager's properties.  The session
id specified will be used as the session id.
If a new session cannot be created for any reason, return
null.

Params:
  • sessionId – The session id which should be used to create the
 new session; if null, the session
 id will be assigned by this method, and available via the getId()
 method of the returned session.
Throws:
Returns:An empty Session object with the given ID or a newly created
        session ID if none was specified
/**
     * Construct and return a new session object, based on the default
     * settings specified by this Manager's properties.  The session
     * id specified will be used as the session id.
     * If a new session cannot be created for any reason, return
     * <code>null</code>.
     *
     * @param sessionId The session id which should be used to create the
     *  new session; if <code>null</code>, the session
     *  id will be assigned by this method, and available via the getId()
     *  method of the returned session.
     * @exception IllegalStateException if a new session cannot be
     *  instantiated for any reason
     *
     * @return An empty Session object with the given ID or a newly created
     *         session ID if none was specified
     */
    public Session createSession(String sessionId);


    
Return the active Session, associated with this Manager, with the
specified session id (if any); otherwise return null.

Params:
  • id – The session id for the session to be returned
Throws:
Returns:the request session or null if a session with the requested ID could not be found
/**
     * Return the active Session, associated with this Manager, with the
     * specified session id (if any); otherwise return <code>null</code>.
     *
     * @param id The session id for the session to be returned
     *
     * @exception IllegalStateException if a new session cannot be
     *  instantiated for any reason
     * @exception IOException if an input/output error occurs while
     *  processing this request
     *
     * @return the request session or {@code null} if a session with the
     *         requested ID could not be found
     */
    public Session findSession(String id) throws IOException;


    
Return the set of active Sessions associated with this Manager.
If this Manager has no active Sessions, a zero-length array is returned.

Returns:All the currently active sessions managed by this manager
/**
     * Return the set of active Sessions associated with this Manager.
     * If this Manager has no active Sessions, a zero-length array is returned.
     *
     * @return All the currently active sessions managed by this manager
     */
    public Session[] findSessions();


    
Load any currently active sessions that were previously unloaded
to the appropriate persistence mechanism, if any.  If persistence is not
supported, this method returns without doing anything.

Throws:
  • ClassNotFoundException – if a serialized class cannot be
 found during the reload
  • IOException – if an input/output error occurs
/**
     * Load any currently active sessions that were previously unloaded
     * to the appropriate persistence mechanism, if any.  If persistence is not
     * supported, this method returns without doing anything.
     *
     * @exception ClassNotFoundException if a serialized class cannot be
     *  found during the reload
     * @exception IOException if an input/output error occurs
     */
    public void load() throws ClassNotFoundException, IOException;


    
Remove this Session from the active Sessions for this Manager.

Params:
  • session – Session to be removed
/**
     * Remove this Session from the active Sessions for this Manager.
     *
     * @param session Session to be removed
     */
    public void remove(Session session);


    
Remove this Session from the active Sessions for this Manager.

Params:
  • session –   Session to be removed
  • update –    Should the expiration statistics be updated
/**
     * Remove this Session from the active Sessions for this Manager.
     *
     * @param session   Session to be removed
     * @param update    Should the expiration statistics be updated
     */
    public void remove(Session session, boolean update);


    
Remove a property change listener from this component.

Params:
  • listener – The listener to remove
/**
     * Remove a property change listener from this component.
     *
     * @param listener The listener to remove
     */
    public void removePropertyChangeListener(PropertyChangeListener listener);


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

Throws:
  • IOException – if an input/output error occurs
/**
     * Save any currently active sessions in the appropriate persistence
     * mechanism, if any.  If persistence is not supported, this method
     * returns without doing anything.
     *
     * @exception IOException if an input/output error occurs
     */
    public void unload() throws IOException;


    
This method will be invoked by the context/container on a periodic
basis and allows the manager to implement
a method that executes periodic tasks, such as expiring sessions etc.

/**
     * This method will be invoked by the context/container on a periodic
     * basis and allows the manager to implement
     * a method that executes periodic tasks, such as expiring sessions etc.
     */
    public void backgroundProcess();


    
Would the Manager distribute the given session attribute? Manager
implementations may provide additional configuration options to control
which attributes are distributable.

Params:
  • name –  The attribute name
  • value – The attribute value
Returns:true if the Manager would distribute the given attribute otherwise false
/**
     * Would the Manager distribute the given session attribute? Manager
     * implementations may provide additional configuration options to control
     * which attributes are distributable.
     *
     * @param name  The attribute name
     * @param value The attribute value
     *
     * @return {@code true} if the Manager would distribute the given attribute
     *         otherwise {@code false}
     */
    public boolean willAttributeDistribute(String name, Object value);


    
When an attribute that is already present in the session is added again under the same name and the attribute implements HttpSessionBindingListener, should HttpSessionBindingListener.valueUnbound(HttpSessionBindingEvent) be called followed by HttpSessionBindingListener.valueBound(HttpSessionBindingEvent)? 
 The default value is false. 
Returns:true if the listener will be notified, false if it will not
/**
     * When an attribute that is already present in the session is added again
     * under the same name and the attribute implements {@link
     * javax.servlet.http.HttpSessionBindingListener}, should
     * {@link javax.servlet.http.HttpSessionBindingListener#valueUnbound(javax.servlet.http.HttpSessionBindingEvent)}
     * be called followed by
     * {@link javax.servlet.http.HttpSessionBindingListener#valueBound(javax.servlet.http.HttpSessionBindingEvent)}?
     * <p>
     * The default value is {@code false}.
     *
     * @return {@code true} if the listener will be notified, {@code false} if
     *         it will not
     */
    public default boolean getNotifyBindingListenerOnUnchangedValue() {
        return false;
    }


    
Configure if HttpSessionBindingListener.valueUnbound(HttpSessionBindingEvent) be called followed by HttpSessionBindingListener.valueBound(HttpSessionBindingEvent) when an attribute that is already present in the session is added again under the same name and the attribute implements HttpSessionBindingListener. 
Params:
  • notifyBindingListenerOnUnchangedValue – true the listener will be called, 
                                             false it will not
/**
     * Configure if
     * {@link javax.servlet.http.HttpSessionBindingListener#valueUnbound(javax.servlet.http.HttpSessionBindingEvent)}
     * be called followed by
     * {@link javax.servlet.http.HttpSessionBindingListener#valueBound(javax.servlet.http.HttpSessionBindingEvent)}
     * when an attribute that is already present in the session is added again
     * under the same name and the attribute implements {@link
     * javax.servlet.http.HttpSessionBindingListener}.
     *
     * @param notifyBindingListenerOnUnchangedValue {@code true} the listener
     *                                              will be called, {@code
     *                                              false} it will not
     */
    public void setNotifyBindingListenerOnUnchangedValue(
            boolean notifyBindingListenerOnUnchangedValue);


    
When an attribute that is already present in the session is added again under the same name and a HttpSessionAttributeListener is configured for the session should HttpSessionAttributeListener.attributeReplaced(HttpSessionBindingEvent) be called? 
 The default value is true. 
Returns:true if the listener will be notified, false if it will not
/**
     * When an attribute that is already present in the session is added again
     * under the same name and a {@link
     * javax.servlet.http.HttpSessionAttributeListener} is configured for the
     * session should
     * {@link javax.servlet.http.HttpSessionAttributeListener#attributeReplaced(javax.servlet.http.HttpSessionBindingEvent)}
     * be called?
     * <p>
     * The default value is {@code true}.
     *
     * @return {@code true} if the listener will be notified, {@code false} if
     *         it will not
     */
    public default boolean getNotifyAttributeListenerOnUnchangedValue() {
        return true;
    }


    
Configure if HttpSessionAttributeListener.attributeReplaced(HttpSessionBindingEvent) when an attribute that is already present in the session is added again under the same name and a HttpSessionAttributeListener is configured for the session. 
Params:
  • notifyAttributeListenerOnUnchangedValue – true the listener will be called, 
                                               false it will not
/**
     * Configure if
     * {@link javax.servlet.http.HttpSessionAttributeListener#attributeReplaced(javax.servlet.http.HttpSessionBindingEvent)}
     * when an attribute that is already present in the session is added again
     * under the same name and a {@link
     * javax.servlet.http.HttpSessionAttributeListener} is configured for the
     * session.
     *
     * @param notifyAttributeListenerOnUnchangedValue {@code true} the listener
     *                                                will be called, {@code
     *                                                false} it will not
     */
    public void setNotifyAttributeListenerOnUnchangedValue(
            boolean notifyAttributeListenerOnUnchangedValue);
}