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Provides a way to identify a user across more than one page request or visit to a Web site.
The servlet engine 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 either by using cookies or by rewriting URLs.
This interface allows servlets to
HttpSession defines methods that
store these types of data:
The servlet can obtain data from the session, modify it,
and return it to the session, as this example shows:
//Get the session object - "request" represents the HTTP servlet request
HttpSession session = request.getSession(true);
//Get the session data value - an Integer object is read from
//the session, incremented, then written back to the session.
//sessiontest.counter identifies values in the session
Integer ival = (Integer) session.getValue("sessiontest.counter");
if (ival==null)
ival = new Integer(1);
else
ival = new Integer(ival.intValue() + 1);
session.putValue("sessiontest.counter", ival);
When an application stores an object in or removes it 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.
An HTTP session represents the server's view of the session. The server considers a session new under any of these conditions:
isNew() method
returns true.
You must write your servlet to handle cases in which
the client has not joined a session. The following code
example calls isNew to determine whether
a session is new. If it is, the server requires the client
to start a session by directing the client to a welcome
page which the user must enter before gaining access to
other pages on the site.
//Get the session object - "request" represents the HTTP servlet request
HttpSession session = request.getSession(true);
//insist that the client starts a session
//before access to data is allowed
//"response" represents the HTTP servlet response
if (session.isNew()) {
response.sendRedirect (welcomeURL);
}
HttpSessionBindingListener,
HttpSessionContext| Method Summary | |
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. |
int |
getMaxInactiveInterval()
Returns the maximum time interval, in seconds, that the servlet engine will keep this session open between client requests. |
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)
Returns the object bound with the specified name in this session or null if no object of that name exists. |
java.lang.String[] |
getValueNames()
Returns an array containing the names of all the objects bound to this session. |
void |
invalidate()
Invalidates this session and unbinds any objects bound to it. |
boolean |
isNew()
Returns true if the Web server has created a session
but the client has not yet joined. |
void |
putValue(java.lang.String name,
java.lang.Object value)
Binds an object to this session, using the name specified. |
void |
removeValue(java.lang.String name)
Removes the object bound with the specified name from this session. |
void |
setMaxInactiveInterval(int interval)
Specifies the maximum length of time, in seconds, that the servlet engine keeps this session if no user requests have been made of the session. |
| Method Detail |
public long getCreationTime()
long integer specifying
when this session was created relative
to 1-1-1970 GMTpublic 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.
The last accessed time can help you manage sessions. For example, the sessions can be sorted according to age to optimize some task.
long integer
representing the last time
the client sent a request associated
with this session, expressed in
milliseconds since 1-1-1970 GMTpublic int getMaxInactiveInterval()
setMaxInactiveInterval method.setMaxInactiveInterval(int)public HttpSessionContext getSessionContext()
public java.lang.Object getValue(java.lang.String name)
name - a string specifying the name of the objectpublic java.lang.String[] getValueNames()
public void invalidate()
public boolean isNew()
true if the Web server has created a session
but the client has not yet joined.
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.true if the
server has created a session,
but the client has not yet joined
public void putValue(java.lang.String name,
java.lang.Object value)
name - the name to which the object is bound;
cannot be nullvalue - the object to be bound; cannot be nullpublic void removeValue(java.lang.String name)
After this method executes, and if the object
implements HttpSessionBindingListener,
the object calls
HttpSessionBindingListener.valueUnbound.
name - the name of the object to
remove from this sessionpublic void setMaxInactiveInterval(int interval)
interval - An integer specifying the number
of seconds
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