JSP nine built-in objects and four scopes
One, nine built-in objects
request request object
response response object
pageContext page context object
session session object
application application object
out output object
config configuration object
page page object
exception exception object
Two, four scopes
···application: acts on the entire project
request: acts on pages between pages
page: works on the entire page
Session: Acts on the session (client and server - request and response session), session timeout or end termination