JavaOmar 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
Store State Somewhere
Server Side?
Makes Server Really Complicated
State per client!
Client Side?
“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
Three Typical Solutions
Cookies
URL Rewriting
Hidden Fields
Handling Cookies
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)
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
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);
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; } }
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”.
Example CodeRepeat Visitor
Using Cookies to Detect First-Time Visitors (Results)
HTTP Cookies
String sID = makeUniqueString();
Hashtable sessionInfo = new Hashtable();
Hashtable globalTable = findTableStoringSessions();
globalTable.put(sID, sessionInfo);
Cookie sessionCookie = new Cookie("JSESSIONID", sID);
response.addCookie(sessionCookie);
1239865610
Credit: cs193i at Standford
HTTP Cookies
String sID = makeUniqueString();
Hashtable sessionInfo = new Hashtable();
Hashtable globalTable = findTableStoringSessions();
globalTable.put(sID, sessionInfo);
Cookie sessionCookie = new Cookie("JSESSIONID", sID);
response.addCookie(sessionCookie);
1239865610
Credit: cs193i at Standford
HTTP Cookies
String sID = makeUniqueString();
Hashtable sessionInfo = new Hashtable();
Hashtable globalTable = findTableStoringSessions();
globalTable.put(sID, sessionInfo);
Cookie sessionCookie = new Cookie("JSESSIONID", sID);
response.addCookie(sessionCookie);
1239865610
Credit: cs193i at Standford
HTTP Cookies
String sID = makeUniqueString();
Hashtable sessionInfo = new Hashtable();
Hashtable globalTable = findTableStoringSessions();
globalTable.put(sID, sessionInfo);
Cookie sessionCookie = new Cookie("JSESSIONID", sID);
response.addCookie(sessionCookie);
1239865610
Credit: cs193i at Standford
HTTP Cookies
String sID = makeUniqueString();
Hashtable sessionInfo = new Hashtable();
Hashtable globalTable = findTableStoringSessions();
globalTable.put(sID, sessionInfo);
Cookie sessionCookie = new Cookie("JSESSIONID", sID);
response.addCookie(sessionCookie);
1239865610
JSESSIONID → 1239865610
Credit: cs193i at Standford
HTTP Cookies
String sID = makeUniqueString();
Hashtable sessionInfo = new Hashtable();
Hashtable globalTable = findTableStoringSessions();
globalTable.put(sID, sessionInfo);
Cookie sessionCookie = new Cookie("JSESSIONID", sID);
response.addCookie(sessionCookie);
1239865610
Set-Cookie: JSESSIONID=1239865610;
Credit: cs193i at Standford
HTTP Cookies
// On request
String sID = getCookieValue("JSESSIONID");Hashtable globalTable = findTableStoringSessions();Hashtable sInfo = (Hashtable) globalTable.get(sID);
// sInfo contains the data related to user
Cookie: JSESSIONID=1239865610;
Credit: cs193i at Standford
HTTP Cookies
// On request
String sID = getCookieValue("JSESSIONID");Hashtable globalTable = findTableStoringSessions();Hashtable sInfo = (Hashtable) globalTable.get(sID);
// sInfo contains the data related to user
Cookie: JSESSIONID=1239865610;
Credit: cs193i at Standford
HTTP Cookies
// On request
String sID = getCookieValue("JSESSIONID");Hashtable globalTable = findTableStoringSessions();Hashtable sInfo = (Hashtable) globalTable.get(sID);
// sInfo contains the data related to user
Cookie: JSESSIONID=1239865610;
1239865610
Credit: cs193i at Standford
Example : Online Book Store
using cookiesnetBeans project -CookieSessionEx
Top Related