Built-in objects of the JSP in a brief overview

JSP brief overview of built-in objects:

(1) HttpServletRequest object class Request

Role: representative of the request object, used to accept client connections through HTTP protocol transmitted to the server-side data.

(2) HttpServletResponse object class Respone

Role: representative of the response object, used to send data to the client

(3) JspWriter out object class

Role: mainly used for the output data to the client; Out of the base class is JspWriter

(4) HttpSession session class object

Role: The main difference is used to save the information for each user, the session associated with the request; session state to maintain a Web application developers must face.

(5) ServletContex class application object

Role: Mainly used to store user information, the code fragment of operating environment; it is a shared built-in objects, that is, a container of multiple users share a single application object, so the stored information is shared by all users.

(6) PageContext class PageContext object

Role: Managing Web properties, packaging page for the JSP page context, management is the visible part of the JSP in particular access to the named object, its creation and initialization is done by the container.

(7) ServletConfig class Config object

Role: Configuration object code fragments that Servlet configuration.

(8) Object class Page (the equivalent of this) object

Role: processing JSP page is an instance of Object class, refers to an instance of JSP implementation class, that it is also the JSP itself, and only within the JSP page is legitimate.

(9) Exception

Role: JSP file execution errors and exceptions only in the error page where it can be used, provided that: where in the page directive to have the page isErrorPage = true; such as:

a.jsp:



error.jsp:



Are: the error.jsp page can be built using the exception object, use the following:

Note: pageContext attribute default in the current page is shared;

session of the property is in the current session is shared;

ServletContext object is that it is all the pages are shared;

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