Hi I'm pretty new to the servlets and I'm wondering what is the difference between using: HttpServletRequest.getSession().setAttribute() and HttpServletRequest.setAttribute() I have read the javadoc that getSession will create a session if theres not one, but i dont understand why a session is not there if I have a HttpServletRequest object and hence the use of the getSession method. Any advice appriciated Thanks
Two things here. Firstly, the two statements do different things. The former creates a session attribute, while the latter creates a request attribute. The difference is that session attributes live as long as the session lives, so the second page request of the same user has access to session attributes that were set during the first page request. Request attributes, on the other hand, only live for the duration of the current request; once the response is sent back to the browser, they're gone.
As to your second question, sessions are optional. Not every web app uses them, or wants to use them. It makes sense to only create them if the web app code explicitly asks for them.
HttpServletRequest.getSession().setAttribute() sets an attribute in session scope, while HttpServletRequest.setAttribute() sets the attribute in request scope. If an attribute is set using the first it will be available for the whole session across the multiple requests. For the second it will be available only for a given request.
For more understanding, read the difference between request and session.