JSP built-in Object Description

JSP provides some built-in objects to simplify page development. These built-in objects do not need to be instantiated and are implemented and managed by containers.
1. Out object: It mainly outputs data to the client
2. Request object: requests from the client are encapsulated by the request object after being processed by the servlet container. The request object can be used to obtain information such as the header, client address, and protocol.
3. Response object: it encapsulates the response generated by JSP and is then sent to the client to respond to the customer's request.
4. Session Object: it is used to save information of each user, so as to track the operation status of each user
5. pagecontext object: It wraps the page context for JSP pages and manages access to named objects in special visible parts of JSP
6. Application object: The application object stores information for multiple applications. This object is automatically created when the server starts. All users share an application object.
7. config object: it indicates the servlet configuration. When an sverlet is initialized, the container passes some information to the sverlet through this object.
8. Page Object: The page object is the JSP page, which is valid on the JSP page.
9. Exception object: It indicates an exception during running and can be used only on the error page.