/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you under the Apache License, Version 2.0 (the

  * "License"); you may not use this file except in compliance

  * with the License.  You may obtain a copy of the License at

  *

  *     http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing,

  * software distributed under the License is distributed on an

  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

  * KIND, either express or implied.  See the License for the

  * specific language governing permissions and limitations

  * under the License.

  */

 package org.apache.shiro.session;

 import java.io.Serializable;

 import java.util.Collection;

 import java.util.Date;

 /**

  * A {@code Session} is a stateful data context associated with a single Subject (user, daemon process,

  * etc) who interacts with a software system over a period of time.

  * <p/>

  * A {@code Session} is intended to be managed by the business tier and accessible via other

  * tiers without being tied to any given client technology.  This is a <em>great</em> benefit to Java

  * systems, since until now, the only viable session mechanisms were the

  * {@code javax.servlet.http.HttpSession} or Stateful Session EJB's, which many times

  * unnecessarily coupled applications to web or ejb technologies.

  *

  * @since 0.1

  */

 public interface Session {

     /**

      * Returns the unique identifier assigned by the system upon session creation.

      * <p/>

      * All return values from this method are expected to have proper {@code toString()},

      * {@code equals()}, and {@code hashCode()} implementations. Good candidates for such

      * an identifier are {@link java.util.UUID UUID}s, {@link java.lang.Integer Integer}s, and

      * {@link java.lang.String String}s.

      *

      * @return The unique identifier assigned to the session upon creation.

      */

     Serializable getId();

     /**

      * Returns the time the session was started; that is, the time the system created the instance.

      *

      * @return The time the system created the session.

      */

     Date getStartTimestamp();

     /**

      * Returns the last time the application received a request or method invocation from the user associated

      * with this session.  Application calls to this method do not affect this access time.

      *

      * @return The time the user last interacted with the system.

      * @see #touch()

      */

     Date getLastAccessTime();

     /**

      * Returns the time in milliseconds that the session session may remain idle before expiring.

      * <ul>

      * <li>A negative return value means the session will never expire.</li>

      * <li>A non-negative return value (0 or greater) means the session expiration will occur if idle for that

      * length of time.</li>

      * </ul>

      * <b>*Note:</b> if you are used to the {@code HttpSession}'s {@code getMaxInactiveInterval()} method, the scale on

      * this method is different: Shiro Sessions use millisecond values for timeout whereas

      * {@code HttpSession.getMaxInactiveInterval} uses seconds.  Always use millisecond values with Shiro sessions.

      *

      * @return the time in milliseconds the session may remain idle before expiring.

      * @throws InvalidSessionException if the session has been stopped or expired prior to calling this method.

      * @since 0.2

      */

     long getTimeout() throws InvalidSessionException;

     /**

      * Sets the time in milliseconds that the session may remain idle before expiring.

      * <ul>

      * <li>A negative value means the session will never expire.</li>

      * <li>A non-negative value (0 or greater) means the session expiration will occur if idle for that

      * length of time.</li>

      * </ul>

      * <p/>

      * <b>*Note:</b> if you are used to the {@code HttpSession}'s {@code getMaxInactiveInterval()} method, the scale on

      * this method is different: Shiro Sessions use millisecond values for timeout whereas

      * {@code HttpSession.getMaxInactiveInterval} uses seconds.  Always use millisecond values with Shiro sessions.

      *

      * @param maxIdleTimeInMillis the time in milliseconds that the session may remain idle before expiring.

      * @throws InvalidSessionException if the session has been stopped or expired prior to calling this method.

      * @since 0.2

      */

     void setTimeout(long maxIdleTimeInMillis) throws InvalidSessionException;

     /**

      * Returns the host name or IP string of the host that originated this session, or {@code null}

      * if the host is unknown.

      *

      * @return the host name or IP string of the host that originated this session, or {@code null}

      *         if the host address is unknown.

      */

     String getHost();

     /**

      * Explicitly updates the {@link #getLastAccessTime() lastAccessTime} of this session to the current time when

      * this method is invoked.  This method can be used to ensure a session does not time out.

      * <p/>

      * Most programmers won't use this method directly and will instead rely on the last access time to be updated

      * automatically as a result of an incoming web request or remote procedure call/method invocation.

      * <p/>

      * However, this method is particularly useful when supporting rich-client applications such as

      * Java Web Start appp, Java or Flash applets, etc.  Although rare, it is possible in a rich-client

      * environment that a user continuously interacts with the client-side application without a

      * server-side method call ever being invoked.  If this happens over a long enough period of

      * time, the user's server-side session could time-out.  Again, such cases are rare since most

      * rich-clients frequently require server-side method invocations.

      * <p/>

      * In this example though, the user's session might still be considered valid because

      * the user is actively "using" the application, just not communicating with the

      * server. But because no server-side method calls are invoked, there is no way for the server

      * to know if the user is sitting idle or not, so it must assume so to maintain session

      * integrity.  This {@code touch()} method could be invoked by the rich-client application code during those

      * times to ensure that the next time a server-side method is invoked, the invocation will not

      * throw an {@link ExpiredSessionException ExpiredSessionException}.  In short terms, it could be used periodically

      * to ensure a session does not time out.

      * <p/>

      * How often this rich-client "maintenance" might occur is entirely dependent upon

      * the application and would be based on variables such as session timeout configuration,

      * usage characteristics of the client application, network utilization and application server

      * performance.

      *

      * @throws InvalidSessionException if this session has stopped or expired prior to calling this method.

      */

     void touch() throws InvalidSessionException;

     /**

      * Explicitly stops (invalidates) this session and releases all associated resources.

      * <p/>

      * If this session has already been authenticated (i.e. the {@code Subject} that

      * owns this session has logged-in), calling this method explicitly might have undesired side effects:

      * <p/>

      * It is common for a {@code Subject} implementation to retain authentication state in the

      * {@code Session}.  If the session

      * is explicitly stopped by application code by calling this method directly, it could clear out any

      * authentication state that might exist, thereby effectively "unauthenticating" the {@code Subject}.

      * <p/>

      * As such, you might consider {@link org.apache.shiro.subject.Subject#logout logging-out} the 'owning'

      * {@code Subject} instead of manually calling this method, as a log out is expected to stop the

      * corresponding session automatically, and also allows framework code to execute additional cleanup logic.

      *

      * @throws InvalidSessionException if this session has stopped or expired prior to calling this method.

      */

     void stop() throws InvalidSessionException;

     /**

      * Returns the keys of all the attributes stored under this session.  If there are no

      * attributes, this returns an empty collection.

      *

      * @return the keys of all attributes stored under this session, or an empty collection if

      *         there are no session attributes.

      * @throws InvalidSessionException if this session has stopped or expired prior to calling this method.

      * @since 0.2

      */

     Collection<Object> getAttributeKeys() throws InvalidSessionException;

     /**

      * Returns the object bound to this session identified by the specified key.  If there is no

      * object bound under the key, {@code null} is returned.

      *

      * @param key the unique name of the object bound to this session

      * @return the object bound under the specified {@code key} name or {@code null} if there is

      *         no object bound under that name.

      * @throws InvalidSessionException if this session has stopped or expired prior to calling

      *                                 this method.

      */

     Object getAttribute(Object key) throws InvalidSessionException;

     /**

      * Binds the specified {@code value} to this session, uniquely identified by the specifed

      * {@code key} name.  If there is already an object bound under the {@code key} name, that

      * existing object will be replaced by the new {@code value}.

      * <p/>

      * If the {@code value} parameter is null, it has the same effect as if

      * {@link #removeAttribute(Object) removeAttribute} was called.

      *

      * @param key   the name under which the {@code value} object will be bound in this session

      * @param value the object to bind in this session.

      * @throws InvalidSessionException if this session has stopped or expired prior to calling

      *                                 this method.

      */

     void setAttribute(Object key, Object value) throws InvalidSessionException;

     /**

      * Removes (unbinds) the object bound to this session under the specified {@code key} name.

      *

      * @param key the name uniquely identifying the object to remove

      * @return the object removed or {@code null} if there was no object bound under the name

      *         {@code key}.

      * @throws InvalidSessionException if this session has stopped or expired prior to calling

      *                                 this method.

      */

     Object removeAttribute(Object key) throws InvalidSessionException;

 }