Question

When I was learning how to create a session in Servlets. I read that Servlet API provides a class called HttpSession to create sessions.

HttpSession session = request.getSession(true);

Then, I was looking at some sample codes and saw this piece of code.

// Get the bean from session.

Customer customer = request.getSession(true).getAttribute("userinfo");

What exactly is happening here? How did they create a session without using the HttpSession class?

Answer 1

The line

Customer customer = request.getSession(true).getAttribute("userinfo");

is equivalent to

HttpSession tempVariable = request.getSession(true);
Customer customer = tempVariable.getAttribute("userinfo");

but without the temporary variable. It’s just method chaining. request.getSession(true) is an expression whose type is HttpSession, since the getSession() method returns a HttpSession. So you can call methods of HttpSession on this expression.

Note that request is an HttpServletRequest, and not an HttpServlet as your question says.