HttpSession源码：
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package javax.servlet.http;
import java.util.Enumeration;
import javax.servlet.ServletContext;
/**
*
* Provides a way to identify a user across more than one page
* request or visit to a Web site and to store information about that user.
*
* <p>The servlet container uses this interface to create a session
* between an HTTP client and an HTTP server. The session persists
* for a specified time period, across more than one connection or
* page request from the user. A session usually corresponds to one
* user, who may visit a site many times. The server can maintain a
* session in many ways such as using cookies or rewriting URLs.
*
* <p>This interface allows servlets to
* <ul>
* <li>View and manipulate information about a session, such as
* the session identifier, creation time, and last accessed time
* <li>Bind objects to sessions, allowing user information to persist
* across multiple user connections
* </ul>
*
* <p>When an application stores an object in or removes an object from a
* session, the session checks whether the object implements
* {@link HttpSessionBindingListener}. If it does,
* the servlet notifies the object that it has been bound to or unbound
* from the session. Notifications are sent after the binding methods complete.
* For session that are invalidated or expire, notifications are sent after
* the session has been invalidated or expired.
*
* <p> When container migrates a session between VMs in a distributed container
* setting, all session attributes implementing the {@link HttpSessionActivationListener}
* interface are notified.
*
* <p>A servlet should be able to handle cases in which
* the client does not choose to join a session, such as when cookies are
* intentionally turned off. Until the client joins the session,
* <code>isNew</code> returns <code>true</code>. If the client chooses
* not to join
* the session, <code>getSession</code> will return a different session
* on each request, and <code>isNew</code> will always return
* <code>true</code>.
*
* <p>Session information is scoped only to the current web application
* (<code>ServletContext</code>), so information stored in one context
* will not be directly visible in another.
*
* @author Various
*
* @see HttpSessionBindingListener
* @see HttpSessionContext
*/
public interface HttpSession {
/**
*
* Returns the time when this session was created, measured
* in milliseconds since midnight January 1, 1970 GMT.
*
* @return a <code>long</code> specifying
* when this session was created,
* expressed in
* milliseconds since 1/1/1970 GMT
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public long getCreationTime();
/**
* Returns a string containing the unique identifier assigned
* to this session. The identifier is assigned
* by the servlet container and is implementation dependent.
*
* @return a string specifying the identifier
* assigned to this session
*/
public String getId();
/**
*
* Returns the last time the client sent a request associated with
* this session, as the number of milliseconds since midnight
* January 1, 1970 GMT, and marked by the time the container received the
* request.
*
* <p>Actions that your application takes, such as getting or setting
* a value associated with the session, do not affect the access
* time.
*
* @return a <code>long</code>
* representing the last time
* the client sent a request associated
* with this session, expressed in
* milliseconds since 1/1/1970 GMT
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public long getLastAccessedTime();
/**
* Returns the ServletContext to which this session belongs.
*
* @return The ServletContext object for the web application
* @since Servlet 2.3
*/
public ServletContext getServletContext();
/**
* Specifies the time, in seconds, between client requests before the
* servlet container will invalidate this session.
*
* <p>An <tt>interval</tt> value of zero or less indicates that the
* session should never timeout.
*
* @param interval An integer specifying the number
* of seconds
*/
public void setMaxInactiveInterval(int interval);
/**
* Returns the maximum time interval, in seconds, that
* the servlet container will keep this session open between
* client accesses. After this interval, the servlet container
* will invalidate the session. The maximum time interval can be set
* with the <code>setMaxInactiveInterval</code> method.
*
* <p>A return value of zero or less indicates that the
* session will never timeout.
*
* @return an integer specifying the number of
* seconds this session remains open
* between client requests
*
* @see #setMaxInactiveInterval
*/
public int getMaxInactiveInterval();
/**
*
* @deprecated As of Version 2.1, this method is
* deprecated and has no replacement.
* It will be removed in a future
* version of the Java Servlet API.
*
*/
public HttpSessionContext getSessionContext();
/**
* Returns the object bound with the specified name in this session, or
* <code>null</code> if no object is bound under the name.
*
* @param name a string specifying the name of the object
*
* @return the object with the specified name
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public Object getAttribute(String name);
/**
* @deprecated As of Version 2.2, this method is
* replaced by {@link #getAttribute}.
*
* @param name a string specifying the name of the object
*
* @return the object with the specified name
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public Object getValue(String name);
/**
* Returns an <code>Enumeration</code> of <code>String</code> objects
* containing the names of all the objects bound to this session.
*
* @return an <code>Enumeration</code> of
* <code>String</code> objects specifying the
* names of all the objects bound to
* this session
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public Enumeration<String> getAttributeNames();
/**
* @deprecated As of Version 2.2, this method is
* replaced by {@link #getAttributeNames}
*
* @return an array of <code>String</code>
* objects specifying the
* names of all the objects bound to
* this session
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public String[] getValueNames();
/**
* Binds an object to this session, using the name specified.
* If an object of the same name is already bound to the session,
* the object is replaced.
*
* <p>After this method executes, and if the new object
* implements <code>HttpSessionBindingListener</code>,
* the container calls
* <code>HttpSessionBindingListener.valueBound</code>. The container then
* notifies any <code>HttpSessionAttributeListener</code>s in the web
* application.
* <p>If an object was already bound to this session of this name
* that implements <code>HttpSessionBindingListener</code>, its
* <code>HttpSessionBindingListener.valueUnbound</code> method is called.
*
* <p>If the value passed in is null, this has the same effect as calling
* <code>removeAttribute()<code>.
*
*
* @param name the name to which the object is bound;
* cannot be null
*
* @param value the object to be bound
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public void setAttribute(String name, Object value);
/**
* @deprecated As of Version 2.2, this method is
* replaced by {@link #setAttribute}
*
* @param name the name to which the object is bound;
* cannot be null
*
* @param value the object to be bound; cannot be null
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public void putValue(String name, Object value);
/**
* Removes the object bound with the specified name from
* this session. If the session does not have an object
* bound with the specified name, this method does nothing.
*
* <p>After this method executes, and if the object
* implements <code>HttpSessionBindingListener</code>,
* the container calls
* <code>HttpSessionBindingListener.valueUnbound</code>. The container
* then notifies any <code>HttpSessionAttributeListener</code>s in the web
* application.
*
* @param name the name of the object to
* remove from this session
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public void removeAttribute(String name);
/**
* @deprecated As of Version 2.2, this method is
* replaced by {@link #removeAttribute}
*
* @param name the name of the object to
* remove from this session
*
* @exception IllegalStateException if this method is called on an
* invalidated session
*/
public void removeValue(String name);
/**
* Invalidates this session then unbinds any objects bound
* to it.
*
* @exception IllegalStateException if this method is called on an
* already invalidated session
*/
public void invalidate();
/**
* Returns <code>true</code> if the client does not yet know about the
* session or if the client chooses not to join the session. For
* example, if the server used only cookie-based sessions, and
* the client had disabled the use of cookies, then a session would
* be new on each request.
*
* @return <code>true</code> if the
* server has created a session,
* but the client has not yet joined
*
* @exception IllegalStateException if this method is called on an
* already invalidated session
*/
public boolean isNew();
}
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