JSP Predefined Variables

request:

· HttpServletRequest associated with the HTTP request the user made when asking for the .jsp file.

· Can use all of the methods of this class, in same way did with a Servlet.

o e.g Can get parameters passed via GET or POST using the getParameter() method.

o Can get HTTP headers (Cookies, etc)

response:

· HttpServletResponse associated with the response to be sent to the client.

· Can set HTTP status codes, response headers

· NOTE: do not retrive an OutputStream instance to produceoutput to be sent to client….ALREADY exists a predefined variable, called out

out:

· PrintWriter instance used to send output back to the client.

· NOTE: is buffered (actually an instance of subclass of PrintWriter called JspWriter).

· Typically, used in scriplets (not in expressions …as these automatically go to the OutputStream!!!)

session:

· HttpSession object associated with the request.

· First time .jsp file invoke, will translate into a servlet and then invoke the servlet, hence creating a session.

· Use methods to get information about session.

application:

· ServletContext instance you get in Servlet when invoking getServletConfig().getContext().

· Can use to store persistent data that ALL Servlets (not just this one) running in the server’s Servlet Engine can share.

· Uses methods setAttribute() and getAttribute().

· Recall: your server may or may not be configured to support this.

config:

· ServletConfig instance for the produced Servlet.

pageContext:

· PageContext object associated with page produced by Servlet.

· NOTE: this class exists only for Servlet’s produced by JSP.

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