Advance java session 8

Advance java session 8

• 1.
  Handling Session in Servlets
• 2.
  Agenda • Implementing sessiontracking from scratch • Using basic session tracking • Understanding Session tracking api • URLEncoding • Tracking user counts
• 3.
  Session Management • Differentways to manage Sessions - Using Cookie(discussed in prev chapter) - Using HttpSession Object - Using URL Rewriting - Using HiddenFields
• 4.
  Session Management • Cookieis the default method of handling session in JEE • If the client browser does not support cookie creation then the URL rewriting is the only option
• 5.
  Hidden Fields • Awebserver can send hidden HTML form fields - <input type=“hidden” name=“sessionid” value=‘123”> • When form submitted the value will be send to the Server • But hyperlink does not result in form submission • Generally not used for Session Tracking
• 6.
  URL Rewriting • Wecan append some extra data at the end of each URL that identifies the session - http://www.talentedge.in/file.jsp;sessionid=123 • URL rewriting is better alternate for client that do not support cookies • Must encode all URL • All pages must be dynamically generated(JSP)
• 7.
  URL Rewriting? how •Session tracking code: - No change • Code that generates hypertext links back to same site: - Pass URL through response.encodeURL. • If server is using cookies, this returns URL unchanged • If server is using URL rewriting, this appends the session info to the URL • E.g.: - String url = "order-page.html"; - url = response.encodeURL(url); • Code that does sendRedirect to own site: - Pass URL through response.encodeRedirectURL
• 8.
  HttpSession • Servlet apiprovides HttpSession Object - Request.getSession() • This will return the current session existing with this request. • If no session exists then create a new one - request.getSession(true) • Same as request.getSession() - Request.getSession(false) • This will return the current session existing with this request • If no session exits then it will return null
• 9.
  HttpSession (cont) • Accessthe session object - Call request.getSession to get HttpSession object - This is a hashtable associated with the user • Look up information associated with a session. - Call getAttribute on the HttpSession object, cast the return value to the appropriate type, and check whether the result is null. • Store information in a session. - Use setAttribute with a key and a value. • Discard session data. - Call removeAttribute discards a specific value. - Call invalidate to discard an entire session.
• 10.
  HttpSession Methods(Cont) • isNew -Determines if session is new to client (not to page) • getCreationTime - Returns time at which session was first created • getLastAccessedTime - Returns time at which session was last sent from client • getMaxInactiveInterval , setMaxInactiveInterval - Gets or sets the amount of time session should go without access before being invalidated • Invalidate - Invalidates current session
• 11.
  HttpSession Methods • getAttribute -Extracts a previously stored value from a session object. - Returns null if no value is associated with given nam • setAttribute - Associates a value with a name. Monitor changes: values implement HttpSessionBindingListener • removeAttribute - Removes values associated with name. • getAttributeNames - Returns names of all attributes in the session. • getId Returns the unique identifier.
• 12.
  Tracking access count publicclass ShowSession extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); HttpSession session = request.getSession(); String heading; Integer accessCount = (Integer)session.getAttribute("accessCount"); if (accessCount == null) { accessCount = new Integer(0); heading = "Welcome, Newcomer"; } else { heading = "Welcome Back"; accessCount = new Integer(accessCount.intValue() + 1); } session.setAttribute("accessCount", accessCount);
• 13.
  Tracking access count PrintWriterout = response.getWriter(); out.println (docType +"<HTML>n" + "<HEAD><TITLE>" + title + "</TITLE></HEAD>n" + "<BODY BGCOLOR="#FDF5E6">n" + "<CENTER>n" + "<H1>" + heading + "</H1>n" + "<H2>Information on Your Session:</H2>n" + "<TABLE BORDER=1>n" + "<TR BGCOLOR="#FFAD00">n" + " <TH>Info Type<TH>Valuen" + " <TD>Number of Previous Accessesn" + " <TD>" + accessCount + "n" + "</TABLE>n" + "</CENTER></BODY></HTML>");
• 14.
  Summary • Sessions donot travel across network - Only unique identifier does • Get the session - request.getSession • Extract data from session - session.getAttribute • Do typecast and check for null • If you cast to a generic type, use @SuppressWarnings
• 15.
  Summary • Put datain session - session.setAttribute • Custom classes in sessions - Should implement Serializable