Head First Servlets and JSP, 2nd Edition

One problem... how does the Container know who the client is?

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.

Because the connections don’t persist, the Container doesn’t recognize that the client making a second request is the same client from a previous request. As far as the Container’s concerned, each request is from a new client.

There are no Dumb Questions

Q:

Q: Why can’t the Container just use the IP address of the client? It’s part of the request, right?

A:

A: Oh, the Container can get the IP address of the request, but does that uniquely identify the client? If you’re on a local IP network, you have a unique IP address, but chances are, that’s not the IP address the outside world sees. To the server, your IP address is the address of the router, so you have the same IP address as everybody else on that network! So that wouldn’t help. You’d have the same problem—the stuff Jim puts in his shopping cart might end up in Pradeep’s cart, and vice versa. So no, IP address isn’t a solution for uniquely ...