The HTTP protocol uses stateless connections. The client browser makes a connection to the server, sends the request, gets the response, and closes the connection. In other words, the connection exists for only a single request/response.

An HttpSession object can hold conversational state across multiple requests from the same client. In other words, it persists for an entire session with a specific client. We can use it to store everything we got back from the client in all the requests the client makes during a session.

Exercise of this week

• (Cookie 1) After accessing /hello-servlet more than once, Welcome back shall be displayed. Try to delete the cookies of localhost in your browser, see what happens while visiting /hello-servlet again.
• (Cookie 2) By default, your browser would accept cookies, so response.encodeURL does not necessarily fall back to URL rewriting. Try to disable the cookies for localhost in your browser.
• Implement log-out for the simple login page.
• Imagine there is a text file that stores the name password information. Please authenticate the user based on this file, and display error message such as wrong password, no such user.

The hint for the last exercise: A sample text file

Tom abc123y
James ut$034u

indicates that user Tom's password is abc123y, and user James's password is ut$034u.

Optional exercise of this week

Implement the remember me for 1 week in our simple login page.