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Http session (Java)
- 1. Seminar Topic Http Session Preparedby- Mrittunjoy Das | MCA – Section (A) ACHARYA INSTITUTE OF TECHNOLOGY
- 2. How to UseSessions • To use a session, first create a session using the HttpServletRequest method getSession(). • Once the session is established, examine and set its properties using the provided methods. • If desired, set the session to time out after being inactive for a defined time period, or invalidate it manually. What we Look further ? • Creating or Accessing a Session • Examining Session Properties • Binding Data to a Session • Invalidating a Session
- 3. Creating or Accessinga Session • To create a new session or gain access to an existing session, use the HttpServletRequest method getSession() • HttpSession mySession = request.getSession(); • getSession() - Returns the current session associated with this request, or if the request does not have a session, creates one. • getSession(boolean create) - Returns the current HttpSession associated with this request or, if there is no current session and arument passed is true then it returns a new session. • false parameter to getSession() prevents the servlet from creating a new session if one does not already exist.
- 4. Examining Session Properties •Once a session ID has been established, use the methods in the HttpSession interface to examine session properties, and the methods in the HttpServletRequest interface to examine request properties that relate to the session. HttpSession Method Description getCreationTime() Returns the session time in milliseconds since January 1, 1970, 00:00:00 GMT. getId() Returns the assigned session identifier. An HTTP session's identifier is a unique string that is created and maintained by the server. getLastAccessedTime() Returns the last time the client sent a request carrying the assigned session identifier (or -1 if it’s a new session) in milliseconds since January 1, 1970, 00:00:00 GMT. isNew() Returns a Boolean value indicating if the session is new. It’s a new session if the server has created it and the client has not sent a request to it. This means the client has not acknowledged or joined the session and may not return the correct session identification information when making its next request.
- 5. Contd… HttpServletRequest Method Description getRequestedSessionId()Returns the session ID specified with the request. This may differ from the session ID in the current session if the session ID given by the client is invalid and a new session was created. Returns null if the request does not have a session associated with it. isRequestedSessionIdValid() Checks if the request is associated to a currently valid session. If the session requested is not valid, it is not returned through the getSession() method. isRequestedSessionIdFromCookie() Returns true if the request's session ID provided by the client is a cookie, or falseotherwise. isRequestedSessionIdFromURL() Returns true if the request's session ID provided by the client is a part of a URL, or false otherwise.
- 6. Binding Data toa Session HttpSession Method Description getAttribute() Returns the object bound to a given name in the session, or null if there is no such binding. getAttributeNames() Returns an array of names of all attributes bound to the session. setAttribute() Binds the specified object into the session with the given name. Any existing binding with the same name is overwritten. For an object bound into the session to be distributed it must implement the serializable interface. removeAttribute() Unbinds an object in the session with the given name. If there is no object bound to the given name, this method does nothing.
- 7. Invalidating a Session •Direct the session to invalidate itself automatically after being inactive for a defined time period. • Alternatively, invalidate the session manually with the HttpSession method invalidate(). Invalidating a Session Manually • To invalidate a session manually, simply call the following method: • session.invalidate(); • All objects bound to the session are removed.
- 8. Setting a SessionTimeout In Web.xml Session Configuration <session-config> <session-timeout>30</session-timeout> </session-config>
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