javax.servlet.http
Interface HttpSession

public interface HttpSession

A HttpSession holds session-dependant data on the server side. A servlet can request the servlet by using HttpServletRequest.getSession(...)

The handling of the Session objects is a job done by the server and servlets together.

As follows:

The server maintaines the set of HttpSessions.
The server creates HttpSession on request by a servlet
The server removes all invalidated HttpSessions
The server connects an incoming request with its HttpSession (usually done using cookies)
Servlets manipulate the contents of the HttpSession by adding and removing items.
Servlets ask the server to remove HttpSessions by invalidating them

Since:

Servlet API 2.0

Version:

Servlet API 2.0

Method Summary

long	getCreationTime() Gets this session's creation time in seconds since january 1st 1970.
java.lang.String	getId() Gets the unique session id.
long	getLastAccessedTime() Gets the number of seconds since the previous access of this session.
HttpSessionContext	getSessionContext() Gets this HttpSession's context.
java.lang.Object	getValue(java.lang.String name) Gets a object from the set of name/value pairs in the session.
java.lang.String[]	getValueNames() Get a list of all item names in the session.
void	invalidate() Make this HttpSession unavailable for use by other servlets and tell the server to remove this session.
boolean	isNew() Returns whether this session has been freshly created.
void	putValue(java.lang.String name, java.lang.Object value) Puts a name and value in the HttpSession.
void	removeValue(java.lang.String name) Removes an item from the session.

Method Detail

getCreationTime

public long getCreationTime()
                     throws java.lang.IllegalStateException

Gets this session's creation time in seconds since january 1st 1970.

Returns:

a number of seconds

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

getId

public java.lang.String getId()
                       throws java.lang.IllegalStateException

Gets the unique session id. Every HttpSession has a Id that is unique for this (virtual) http server.

Returns:

The Id

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

getLastAccessedTime

public long getLastAccessedTime()
                         throws java.lang.IllegalStateException

Gets the number of seconds since the previous access of this session. Every time a client's request comes in the server checks (usually by using cookies) which HttpSession object corresponds with this particular client. The server then sets the lastAccessedTime to the current time. (And the isNew flag to false.) If the client has never requested anything with this Session then this method returns -1

Returns:

number of seconds since last access or -1

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

getValue

public java.lang.Object getValue(java.lang.String name)
                          throws java.lang.IllegalStateException

Gets a object from the set of name/value pairs in the session.

Parameters:

name - the name of the item required

Returns:

the value of the item. null if not present.

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

getValueNames

public java.lang.String[] getValueNames()
                                 throws java.lang.IllegalStateException

Get a list of all item names in the session.

Returns:

An array of Strings containing all item names.

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

invalidate

public void invalidate()
                throws java.lang.IllegalStateException

Make this HttpSession unavailable for use by other servlets and tell the server to remove this session. All values bound to this session with putValue() that implement HttpSessionBindingListener will be called with valueUnbound(). Also: make it throw an IllegalStateException when a servlet tries to execute one of its methods.

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

isNew

public boolean isNew()
              throws java.lang.IllegalStateException

Returns whether this session has been freshly created. A servlet can ask the server to give the HttpSession connected with this request/client. The Servlet can use this method to check whether the HttpSession has been newly created or if a HttpSession had already been created for a previous request.

Returns:

Whether this is a new HttpSession

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

putValue

public void putValue(java.lang.String name,
                     java.lang.Object value)
              throws java.lang.IllegalStateException

Puts a name and value in the HttpSession. If the Object implements HttpSessionBindindListener then the valueBound() method of the Object will be called.

Parameters:

name - the name of the item

value - the value of the item

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

removeValue

public void removeValue(java.lang.String name)
                 throws java.lang.IllegalStateException

Removes an item from the session. If the Object implements HttpSessionBindindListener then the valueUnBound() method of the Object will be called.

Parameters:

name - the name of the item.

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0

getSessionContext

public HttpSessionContext getSessionContext()
                                     throws java.lang.IllegalStateException

Gets this HttpSession's context. The context contains information that is the same for all HttpSessions for this (virtual) host.

Returns:

The context

Throws:

java.lang.IllegalStateException - if the session has been invalidated.

Since:

Servlet API 2.0