HttpSession (Servlet and JavaServer Pages API Documentation)
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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
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 invalidatd or expired.
When container migrates a session between VMs in a distributed container
setting, all session atributes 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
,
HttpSessionContext
Method Summary | |
java.lang.Object |
getAttribute(java.lang.String name)
Returns the object bound with the specified name in this session, or null if no object is bound under the name. |
java.util.Enumeration |
getAttributeNames()
Returns an Enumeration of String objects
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. |
java.lang.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 recieved 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. |
java.lang.Object |
getValue(java.lang.String name)
Deprecated. As of Version 2.2, this method is replaced by getAttribute(java.lang.String) . |
java.lang.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 true if the client does not yet know about the
session or if the client chooses not to join the session. |
void |
putValue(java.lang.String name,
java.lang.Object value)
Deprecated. As of Version 2.2, this method is replaced by setAttribute(java.lang.String, java.lang.Object) |
void |
removeAttribute(java.lang.String name)
Removes the object bound with the specified name from this session. |
void |
removeValue(java.lang.String name)
Deprecated. As of Version 2.2, this method is replaced by removeAttribute(java.lang.String) |
void |
setAttribute(java.lang.String name,
java.lang.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. |
Method Detail |
public long getCreationTime()
long
specifying
when this session was created,
expressed in
milliseconds since 1/1/1970 GMT
java.lang.IllegalStateException
- if this method is called on an
invalidated sessionpublic java.lang.String getId()
public long 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 GMTpublic ServletContext getServletContext()
public void setMaxInactiveInterval(int interval)
interval
- An integer specifying the number
of secondspublic int getMaxInactiveInterval()
setMaxInactiveInterval
method.
A negative time indicates the session should never timeout.
setMaxInactiveInterval(int)
public HttpSessionContext getSessionContext()
public java.lang.Object getAttribute(java.lang.String name)
null
if no object is bound under the name.
name
- a string specifying the name of the object
java.lang.IllegalStateException
- if this method is called on an
invalidated sessionpublic java.lang.Object getValue(java.lang.String name)
getAttribute(java.lang.String)
.
name
- a string specifying the name of the object
java.lang.IllegalStateException
- if this method is called on an
invalidated sessionpublic java.util.Enumeration 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 session
java.lang.IllegalStateException
- if this method is called on an
invalidated sessionpublic java.lang.String[] getValueNames()
getAttributeNames()
String
objects specifying the
names of all the objects bound to
this session
java.lang.IllegalStateException
- if this method is called on an
invalidated sessionpublic void setAttribute(java.lang.String name, java.lang.Object value)
After this method executes, and if the new object
implements HttpSessionBindingListener
,
the container calls
HttpSessionBindingListener.valueBound
. The container then
notifies any HttpSessionAttributeListener
s 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 bound
java.lang.IllegalStateException
- if this method is called on an
invalidated session
public void putValue(java.lang.String name, java.lang.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 null
java.lang.IllegalStateException
- if this method is called on an
invalidated sessionpublic void removeAttribute(java.lang.String name)
After this method executes, and if the object
implements HttpSessionBindingListener
,
the container calls
HttpSessionBindingListener.valueUnbound
. The container
then notifies any HttpSessionAttributeListener
s in the web
application.
name
- the name of the object to
remove from this session
java.lang.IllegalStateException
- if this method is called on an
invalidated sessionpublic void removeValue(java.lang.String name)
removeAttribute(java.lang.String)
name
- the name of the object to
remove from this session
java.lang.IllegalStateException
- if this method is called on an
invalidated sessionpublic void invalidate()
java.lang.IllegalStateException
- if this method is called on an
already invalidated sessionpublic boolean 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 joined
java.lang.IllegalStateException
- if this method is called on an
already invalidated session
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