To use sessions in a Java web application, you can use the javax.servlet.http.HttpSession interface. Here is an example code snippet that demonstrates how to set an attribute in a session:

import javax.servlet.http.HttpSession;

HttpSession session = request.getSession(); // Get the current session, or create a new one if none exists
session.setAttribute("myAttribute", "myValue"); // Set an attribute in the session

In this example, the getSession() method is called on the HttpServletRequest object to retrieve the current session, or create a new one if none exists. The setAttribute() method is then called on the HttpSession object to set an attribute with the name "myAttribute" and the value "myValue".

To retrieve an attribute from the session, you can use the getAttribute() method:

import javax.servlet.http.HttpSession;

HttpSession session = request.getSession(); // Get the current session, or create a new one if none exists
String myValue = (String) session.getAttribute("myAttribute"); // Get an attribute from the session

In this example, the getSession() method is called to retrieve the current session, or create a new one if none exists. The getAttribute() method is then called on the HttpSession object to retrieve the value of the "myAttribute" attribute.

Note that sessions can also have a maximum inactive interval, which is the amount of time (in seconds) that a session can remain inactive before it is invalidated. This interval can be set using the setMaxInactiveInterval() method:

import javax.servlet.http.HttpSession;

HttpSession session = request.getSession(); // Get the current session, or create a new one if none exists
session.setMaxInactiveInterval(60 * 60); // Set the maximum inactive interval to 1 hour (in seconds)

In this example, the getSession() method is called to retrieve the current session, or create a new one if none exists. The setMaxInactiveInterval() method is then called on the HttpSession object to set the maximum inactive interval to 1 hour (in seconds).