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This article will explain in detail what the built-in objects in JSP are. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

A brief overview of JSP built-in objects:

(1) Request object of HttpServletRequest class

Function: represents the request object and is mainly used to accept the data transferred from the client to the server through the HTTP protocol connection.

(2) Respone object of HttpServletResponse class

Function: represents the response object and is mainly used to send data to the client

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

(4) session object of HttpSession class

Role: mainly used to save each user information separately, the session associated with the request

Session state maintenance is a problem that Web application developers must face.

(5) application object of ServletContex class

Function: mainly used to save user information, code snippet running environment

It is a shared built-in object, that is, multiple users in a container share an application object, so the saved information is shared by all users.

Function: manage web page properties, wrap the page context for JSP pages, manage access to named objects belonging to the special visible part of the JSP, its creation and initialization are completed by the container.

(7) Config object of ServletConfig class

Purpose: a code snippet configuration object that represents the configuration of Servlet.

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

Role: dealing with JSP pages, is an instance of the Object class, refers to an instance of the JSP implementation class, that is, it is also JSP itself, only within the scope of the JSP page is legal.

(9) Exception

Function: handle errors and exceptions that occur during the execution of JSP files

It can only be used on error pages, as long as there is an isErrorPage=true in the page instruction.

Such as:

A.jsp:

Error.jsp:

Then: you can use the exception built-in object in the error.jsp page as follows:

Note: attributes in pageContext are shared on the current page by default

Properties in session are shared in the current session

The attribute in the ServletContext object is shared for all pages.

This is the end of the article on "what is the built-in object in JSP". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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