SP有9个内置对象，作用分别是什么？

SP refers to the ServletContext object in Java web development, and it has several built-in objects:

1. "application" object represents the entire web application and can be accessed across sessions.
2. "config" object provides access to the web application's configuration information.
3. "context" object represents the ServletContext itself and provides information about the web application container.
4. "pageContext" object provides a way to access the various implicit objects available to a JSP page.
5. "request" object represents an HTTP request and contains information about the client's request.
6. "response" object represents an HTTP response and is used to send data back to the client.
7. "session" object represents a session between the client and server and allows for the storage of information across requests.
8. "out" object is used to write output to the client's browser.
9. "page" object represents the current JSP page being processed.