public interface HttpSession
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.
This interface allows servlets to
 When an application stores an object in or removes an object from a session,
 the session checks whether the object implements
 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.
 
 When container migrates a session between VMs in a distributed container
 setting, all session attributes implementing the
 HttpSessionActivationListener interface are notified.
 
 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, isNew returns true.
 If the client chooses not to join the session, getSession will
 return a different session on each request, and isNew will
 always return true.
 
 Session information is scoped only to the current web application (
 ServletContext), so information stored in one context will not
 be directly visible in another.
HttpSessionBindingListener| Modifier and Type | Method and Description | 
|---|---|
| Object | getAttribute(String name)Returns the object bound with the specified name in this session, or
  nullif no object is bound under the name. | 
| Enumeration<String> | getAttributeNames()Returns an  EnumerationofStringobjects
 containing the names of all the objects bound to this session. | 
| long | getCreationTime()Returns the time when this session was created, measured in milliseconds
 since midnight January 1, 1970 GMT. | 
| String | getId()Returns a string containing the unique identifier assigned to this
 session. | 
| long | getLastAccessedTime()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. | 
| int | getMaxInactiveInterval()Returns the maximum time interval, in seconds, that the servlet container
 will keep this session open between client accesses. | 
| ServletContext | getServletContext()Returns the ServletContext to which this session belongs. | 
| HttpSessionContext | getSessionContext()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. | 
| Object | getValue(String name)Deprecated. 
 As of Version 2.2, this method is replaced by
              getAttribute(java.lang.String). | 
| String[] | getValueNames()Deprecated. 
 As of Version 2.2, this method is replaced by
              getAttributeNames() | 
| void | invalidate()Invalidates this session then unbinds any objects bound to it. | 
| boolean | isNew()Returns  trueif the client does not yet know about the
 session or if the client chooses not to join the session. | 
| void | putValue(String name,
        Object value)Deprecated. 
 As of Version 2.2, this method is replaced by
              setAttribute(java.lang.String, java.lang.Object) | 
| void | removeAttribute(String name)Removes the object bound with the specified name from this session. | 
| void | removeValue(String name)Deprecated. 
 As of Version 2.2, this method is replaced by
              removeAttribute(java.lang.String) | 
| void | setAttribute(String name,
            Object value)Binds an object to this session, using the name specified. | 
| void | setMaxInactiveInterval(int interval)Specifies the time, in seconds, between client requests before the
 servlet container will invalidate this session. | 
long getCreationTime()
long specifying when this session was created,
         expressed in milliseconds since 1/1/1970 GMTIllegalStateException - if this method is called on an invalidated sessionString getId()
IllegalStateException - if this method is called on an invalidated sessionlong getLastAccessedTime()
Actions that your application takes, such as getting or setting a value associated with the session, do not affect the access time.
long representing the last time the client sent a
         request associated with this session, expressed in milliseconds
         since 1/1/1970 GMTIllegalStateException - if this method is called on an invalidated sessionServletContext getServletContext()
void setMaxInactiveInterval(int interval)
interval - An integer specifying the number of secondsint getMaxInactiveInterval()
setMaxInactiveInterval method.
 A zero or negative time indicates that the session should never timeout.setMaxInactiveInterval(int)HttpSessionContext getSessionContext()
Object getAttribute(String name)
null if no object is bound under the name.name - a string specifying the name of the objectIllegalStateException - if this method is called on an invalidated sessionObject getValue(String name)
getAttribute(java.lang.String).name - a string specifying the name of the objectIllegalStateException - if this method is called on an invalidated sessionEnumeration<String> getAttributeNames()
Enumeration of String objects
 containing the names of all the objects bound to this session.Enumeration of String objects
         specifying the names of all the objects bound to this sessionIllegalStateException - if this method is called on an invalidated sessionString[] getValueNames()
getAttributeNames()String objects specifying the names of
         all the objects bound to this sessionIllegalStateException - if this method is called on an invalidated sessionvoid setAttribute(String name, Object value)
 After this method executes, and if the new object implements
 HttpSessionBindingListener, the container calls
 HttpSessionBindingListener.valueBound. The container then
 notifies any HttpSessionAttributeListeners in the web
 application.
 
 If an object was already bound to this session of this name that
 implements HttpSessionBindingListener, its
 HttpSessionBindingListener.valueUnbound method is called.
 
 If the value passed in is null, this has the same effect as calling
 removeAttribute().
name - the name to which the object is bound; cannot be nullvalue - the object to be boundIllegalStateException - if this method is called on an invalidated sessionvoid putValue(String name, Object value)
setAttribute(java.lang.String, java.lang.Object)name - the name to which the object is bound; cannot be nullvalue - the object to be bound; cannot be nullIllegalStateException - if this method is called on an invalidated sessionvoid removeAttribute(String name)
 After this method executes, and if the object implements
 HttpSessionBindingListener, the container calls
 HttpSessionBindingListener.valueUnbound. The container then
 notifies any HttpSessionAttributeListeners in the web
 application.
name - the name of the object to remove from this sessionIllegalStateException - if this method is called on an invalidated sessionvoid removeValue(String name)
removeAttribute(java.lang.String)name - the name of the object to remove from this sessionIllegalStateException - if this method is called on an invalidated sessionvoid invalidate()
IllegalStateException - if this method is called on an already invalidated sessionboolean isNew()
true 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.true if the server has created a session, but the
         client has not yet joinedIllegalStateException - if this method is called on an already invalidated sessionCopyright © 2000-2020 Apache Software Foundation. All Rights Reserved.