Pagecontext,request,session,application of the scope of JSP

Scopes are used to bind data, properties                pagecontext page javax.servlet.jsp.PageContext pagecontext current page range,PageContext object cannot pass parameters to other pages

Request page jump javax.servlet.http.HttpServletRequest request
a request that ranges from one page to another page can be used in Request forwarding
session user javax.servlet.http.HttpSession session
scoped to a user, which fails when the user disconnects from the server, such as closing the browser
Application Global javax.servlet.ServletContext application
scope on server execution service to server shutdown service

Please note when applying1, request and session are based on the HTTP
2,servletcontext and application

same : In fact ServletContext and application are the same, it is equivalent to a class created two different names of variables. In

the ServletContext in the servlet is the Application object. All you have to do is open the JSP in the generated servlet after compilation

the _jspservice () method can see the following declaration:
           ServletContext application = null;

          < c29> application = Pagecontext.getservletcontext ();

Differences: The difference between the two is that application is used in JSPs and ServletContext is used in Servlets. Application and Page

the request session is a built-in object in the JSP, and the property data stored in the background with ServletContext can be

The application object is obtained.

Pagecontext,request,session,application of the scope of JSP