INTERACTIVE WEB SERVICES WITH JAVA

Sessions

Session state is maintained in an HttpSession object:

request.getSession(true) returns the current HttpSession object or generates a new
boolean isNew() - returns true if new session
Object getAttribute(String name) - reads per-session state
void setAttribute(String name, Object value) - writes per-session state
String getId() - session info
long getCreationTime()
long getLastAccessedTime()
void setMaxInactiveInterval(int seconds)

- this resembles the management of shared state.

A typical example:
... HttpSession session = request.getSession(true); ShoppingCart cart = (ShoppingCart) session.getAttribute("shoppingcart"); if (cart==null) { cart = new ShoppingCart(); session.setAttribute("shoppingcart", cart); } addItemToCart(cart); ...

Under the hood: uses cookies or URL rewriting

(Since URL rewriting may be used, URLs to our own Servlets should always be passed through response.encodeURL(String))

Cookies can also be controlled manually...

This is a rather low-level approach - the session flow is not explicit in the code!