Servlet Lesson 7: Relationship between servletcontext httpsession and httpservletrequest

Course objectives:

① Understand the relationship between servletcontext httpsession and httpservletrequest in Servlet

② Understand how to use them

Concepts:

1. [commonalities] regardless of the scope of the object, the shared variables and methods for obtaining variables are consistent.
-Setattribute ("varname", OBJ );
-Getattribute ("varname ");
2. Scope of Variables
Servletcontext-Maximum range, application-level, all applications can access
Httpsession-second, the session level can be accessed in the current browser [no matter how many windows are opened in the same browser], but it will not work if you change the browser, you must re-create the session
Httpservletrequest-minimum range, request level, request end, and variable scope [that is, only one access, access is complete, and this is also done]

3. Instance

The preceding three data settings are as follows:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {   // 1            ServletContext sc = this.getServletContext();            sc.setAttribute("sc_name", "sc_value");            // 2            HttpSession session = request.getSession();            session.setAttribute("session_name", "session_value");            // 3            request.setAttribute("request_name", "request_value");                   String sc_value = (String) sc.getAttribute("sc_name");            String session_value = (String) session.getAttribute("session_name");            String request_value = (String) request.getAttribute("request_name");          System.out.println(sc_value+":"+session_value+":"+request_value);                       // request.getRequestDispatcher("MyServlet2").forward(request, response);        }

Obtain servlet2:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {           ServletContext sc = this.getServletContext();            HttpSession session = request.getSession();                  String sc_value = (String) sc.getAttribute("sc_name");            String session_value = (String) session.getAttribute("session_name");            String request_value = (String) request.getAttribute("request_name");                 System.out.println(sc_value+":"+session_value+":"+request_value);}

Conclusion:

Httpservletrequest is only a browser access, unless the servlet is processed, such

request.getRequestDispatcher("MyServlet2").forward(request, response);

It will be passed.

Sessions are used in the same browser to call data from each other.

The entire application of servletcontext can access