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Java

Java. Omar Rana University of South Asia. Revisiting Session Tracking. HTTP is a stateless protocol Every request is considered independent of every other request Many web applications need to maintain a conversational state with the client A shopping cart is a classic example.

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Java

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  1. Java Omar Rana University of South Asia

  2. Revisiting Session Tracking • HTTP is a stateless protocol • Every request is considered independent of every other request • Many web applications need to maintain a conversational state with the client • A shopping cart is a classic example

  3. Store State Somewhere • Server Side? • Makes Server Really Complicated • State per client! • Client Side?

  4. “Post-Notes” • Server puts little notes on the client side • When client submits the next form, it also (unknowingly) submits these little notes • Server reads the notes, remembers who the client is

  5. Three Typical Solutions • Cookies • URL Rewriting • Hidden Fields

  6. Handling Cookies

  7. Potential of Cookies • Idea • Web server sends a simple name-value pair to client (web browser etc.) • Saved by the client • Later, Client returns same name and value when it connects to same site (or same domain, depending on cookie settings)

  8. Potential of Cookies • Typical Uses of Cookies • Identifying a user during an e-commerce session • Servlets have a higher-level API for this task • Avoiding username and password • Customizing a site • Focused advertising

  9. Sending Cookies to Browser • Create a Cookie object Cookie c = new Cookie("name", "value"); • Set the Maximum age etc • Cookie persists on disk c.setMaxAge(seconds); // Set other attributes. • Place the Cookie into HTTP response • If you forget this step, no cookie will be sent to the browser response.addCookie(c);

  10. Reading Cookies from Browser • To read incoming cookies, get them from request object Cookie[] cookies = request.getCookies(); • Once you have an array of cookies, you can iterate over it • Use getName and getValue to retrieve cookie name & value respectively for(int i=0; i<cookies.length; i++) { Cookie c = cookies[i]; if (c.getName().equals("someName")){ // doSomethingWith cookie break; } }

  11. Example 1: RepeatVisitor • This servlet checks for a unique cookie, named “repeat”. • If the cookie is present, servlet says “Welcome Back” • Otherwise, servlet says “Welcome Aboard”.

  12. Example CodeRepeat Visitor

  13. Using Cookies to Detect First-Time Visitors (Results)

  14. HTTP Cookies 1239865610 String sID = makeUniqueString(); Hashtable sessionInfo = new Hashtable(); Hashtable globalTable = findTableStoringSessions(); globalTable.put(sID, sessionInfo); Cookie sessionCookie = new Cookie("JSESSIONID", sID); response.addCookie(sessionCookie); Credit: cs193i at Standford

  15. HTTP Cookies 1239865610 String sID = makeUniqueString(); Hashtable sessionInfo = new Hashtable(); Hashtable globalTable = findTableStoringSessions(); globalTable.put(sID, sessionInfo); Cookie sessionCookie = new Cookie("JSESSIONID", sID); response.addCookie(sessionCookie); Credit: cs193i at Standford

  16. HTTP Cookies 1239865610 String sID = makeUniqueString(); Hashtable sessionInfo = new Hashtable(); Hashtable globalTable = findTableStoringSessions(); globalTable.put(sID, sessionInfo); Cookie sessionCookie = new Cookie("JSESSIONID", sID); response.addCookie(sessionCookie); Credit: cs193i at Standford

  17. HTTP Cookies 1239865610 String sID = makeUniqueString(); Hashtable sessionInfo = new Hashtable(); Hashtable globalTable = findTableStoringSessions(); globalTable.put(sID, sessionInfo); Cookie sessionCookie = new Cookie("JSESSIONID", sID); response.addCookie(sessionCookie); Credit: cs193i at Standford

  18. HTTP Cookies 1239865610 JSESSIONID → 1239865610 String sID = makeUniqueString(); Hashtable sessionInfo = new Hashtable(); Hashtable globalTable = findTableStoringSessions(); globalTable.put(sID, sessionInfo); Cookie sessionCookie = new Cookie("JSESSIONID", sID); response.addCookie(sessionCookie); Credit: cs193i at Standford

  19. HTTP Cookies 1239865610 Set-Cookie: JSESSIONID=1239865610; String sID = makeUniqueString(); Hashtable sessionInfo = new Hashtable(); Hashtable globalTable = findTableStoringSessions(); globalTable.put(sID, sessionInfo); Cookie sessionCookie = new Cookie("JSESSIONID", sID); response.addCookie(sessionCookie); Credit: cs193i at Standford

  20. HTTP Cookies Cookie: JSESSIONID=1239865610; // On request String sID = getCookieValue("JSESSIONID"); Hashtable globalTable = findTableStoringSessions(); Hashtable sInfo = (Hashtable) globalTable.get(sID); // sInfo contains the data related to user Credit: cs193i at Standford

  21. HTTP Cookies Cookie: JSESSIONID=1239865610; // On request String sID = getCookieValue("JSESSIONID"); Hashtable globalTable = findTableStoringSessions(); Hashtable sInfo = (Hashtable) globalTable.get(sID); // sInfo contains the data related to user Credit: cs193i at Standford

  22. HTTP Cookies 1239865610 Cookie: JSESSIONID=1239865610; // On request String sID = getCookieValue("JSESSIONID"); Hashtable globalTable = findTableStoringSessions(); Hashtable sInfo = (Hashtable) globalTable.get(sID); // sInfo contains the data related to user Credit: cs193i at Standford

  23. Example : Online Book Storeusing cookies netBeans project -CookieSessionEx

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