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Interface HttpSession

public interfaceHttpSession

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.

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

• View and manipulate information about a session, such as the session identifier, creation time, and last accessed time
• Bind objects to sessions, allowing user information to persist across multiple user connections

When an application stores an object in or removes an object from a session, the session checks whether the object implementsHttpSessionBindingListener. 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 invalidatd or expired.

When container migrates a session between VMs in a distributed container setting, all session atributes implementing theHttpSessionActivationListener 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 returnstrue. If the client chooses not to join the session,getSession will return a different session on each request, andisNew will always returntrue.

Session information is scoped only to the current web application (ServletContext), so information stored in one context will not be directly visible in another.

See Also:

HttpSessionBindingListener,HttpSessionContext

getCreationTime

public longgetCreationTime()

Returns the time when this session was created, measured in milliseconds since midnight January 1, 1970 GMT.

Returns:

along specifying when this session was created,expressed in milliseconds since 1/1/1970 GMT

Throws:

java.lang.IllegalStateException - if this method is called on aninvalidated session

getId

public java.lang.StringgetId()

Returns a string containing the unique identifier assigned to this session. The identifier is assigned by the servlet container and is implementation dependent.

Returns:

a string specifying the identifierassigned to this session

getLastAccessedTime

public longgetLastAccessedTime()

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 recieved the request.

Actions that your application takes, such as getting or setting a value associated with the session, do not affect the access time.

Returns:

alongrepresenting the last time the client sent a request associatedwith this session, expressed in milliseconds since 1/1/1970 GMT

getServletContext

publicServletContextgetServletContext()

Returns the ServletContext to which this session belongs.

Returns:

The ServletContext object for the web application

Since:

2.3

setMaxInactiveInterval

public voidsetMaxInactiveInterval(int interval)

Specifies the time, in seconds, between client requests before the servlet container will invalidate this session. A negative time indicates the session should never timeout.

Parameters:

interval - An integer specifying the number of seconds

getMaxInactiveInterval

public intgetMaxInactiveInterval()

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 thesetMaxInactiveInterval method. A negative time indicates the session should never timeout.

Returns:

an integer specifying the number ofseconds this session remains openbetween client requests

See Also:

setMaxInactiveInterval(int)

getSessionContext

publicHttpSessionContextgetSessionContext()

Deprecated. As of Version 2.1, this method isdeprecated and has no replacement.It will be removed in a futureversion of the Java Servlet API.

getAttribute

public java.lang.ObjectgetAttribute(java.lang.String name)

Returns the object bound with the specified name in this session, ornull if no object is bound under the name.

Parameters:

name - a string specifying the name of the object

Returns:

the object with the specified name

Throws:

java.lang.IllegalStateException - if this method is called on aninvalidated session

getValue

public java.lang.ObjectgetValue(java.lang.String name)

Deprecated. As of Version 2.2, this method is replaced bygetAttribute(java.lang.String).

Parameters:

name - a string specifying the name of the object

Returns:

the object with the specified name

Throws:

java.lang.IllegalStateException - if this method is called on aninvalidated session

getAttributeNames

public java.util.EnumerationgetAttributeNames()

Returns anEnumeration ofString objects containing the names of all the objects bound to this session.

Returns:

anEnumeration ofString objects specifying thenames of all the objects bound tothis session

Throws:

java.lang.IllegalStateException - if this method is called on aninvalidated session

getValueNames

public java.lang.String[]getValueNames()

Deprecated. As of Version 2.2, this method is replaced bygetAttributeNames()

Returns:

an array ofStringobjects specifying thenames of all the objects bound tothis session

Throws:

java.lang.IllegalStateException - if this method is called on aninvalidated session

setAttribute

public voidsetAttribute(java.lang.String name,                         java.lang.Object value)

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.

After this method executes, and if the new object implementsHttpSessionBindingListener, the container callsHttpSessionBindingListener.valueBound. The container then notifies anyHttpSessionAttributeListeners in the web application.

If an object was already bound to this session of this name that implementsHttpSessionBindingListener, itsHttpSessionBindingListener.valueUnbound method is called.

If the value passed in is null, this has the same effect as callingremoveAttribute().

Parameters:

name - the name to which the object is bound;cannot be null

value - the object to be bound

Throws:

java.lang.IllegalStateException - if this method is called on aninvalidated session

public voidputValue(java.lang.String name,                     java.lang.Object value)

public voidremoveAttribute(java.lang.String name)

public voidremoveValue(java.lang.String name)

public voidinvalidate()

public booleanisNew()