HttpSession

What is HttpSession?

• HttpSession is a part of Java’s Servlet API that helps a web application temporarily store and remember user-specific data (like name, email, role, etc.) across multiple requests (pages).

• Httpsession is used store data per user across multiple Http request(like web app remember a user's data while they move between pages)
  .it helps for spring boot remember a user between requests/pages like a temporary memory for each logged in user.

• Httpsession is interface ,

• memory Location: server side

• Timeout duration: Default 30 min

• Store format:key-value(string-object)

• Real-life usage:Login.cart,dashboard,preferences.

when user login in , you can store their name in the session:
session.setAttribute("key", value);
session.setAttribute("username", "Prasanth");
Later, another method ,you can get it back:
String name = (String) session.getAttribute("username");
session.getAttribute("key");

• Even though user movers between pages, their name stays stored in the session , until that user log out or session expires.

why to use HttpSession?

• Because Http is stateless -> like by default , each request does not remember anything about previous ones.
  so we use HttpSession to:
  useCase:-

• user login -> keep user info save across pages

• shoppig cart -> store selected item temporarily.

• preference -> store user setting ,them,laguage

• Prevent re-login -> Avoid asking for details again and agian.

Why HttpSession Is Useful?

• Avoids using database for every small detail
• Works even if user switches pages
• Fast, lightweight, temporary (auto clears after timeout)

With Session?

• You log in once, and your info is remembered until you:

1. Logout Or close the browser Or session times out

Stores data like:

• username
• user ID
• shopping cart
• user preference

Without Session?

• Every page would forget who you are.
• You’d have to log in again and again

Example:

• You visit a login page → enter name → click login
• The next page doesn't remember what you did earlier unless you store it (like using HttpSession)

Features of HttpSession:

• Stores user data => Temporarily stores data for each user (e.g., login info, cart)
• Unique per user => Each user gets a separate session
• Set & get values => You can store and retrieve values using setAttribute / getAttribute
• Auto session ID=>Automatically assigns a unique session ID to each user Secure Can be configured to expire or invalidate when needed.

Where is it stored?

• Data is stored on the server side (in RAM or temporary session storage)
• Only the session ID is sent to the client (browser) via a cookie.

Duration of Session (Timeout)
Type:-

1. Default timeout=>Usually 30 minutes (can be changed in configuration)
2. Manually expired =>You can call session.invalidate(); to end the session 3.Configurable Set time using session.setMaxInactiveInterval(600); // 10 min

Where it comes from?

• HttpSession is an interface

  Comes from the jakarta.servlet.http.HttpSession package
(Earlier it was javax.servlet.http.HttpSession)

How to use it?
// Store data
session.setAttribute("username", "Prasanth");

// Get data
String name = (String) session.getAttribute("username");

// Remove data
session.removeAttribute("username");

// Invalidate session
session.invalidate();