Following are the implicit EL (Expression Language) objects:-
Page Context: The context for the JSP page.
Provides access to various objects for instance:-
servletContext: The context for the JSP page's servlet and any web components contained in the same application.
session: The session object for the client.
request: The request triggering the execution of the JSP page.
response: The response returned by the JSP page. See Constructing Responses.
In addition, several implicit objects are available that allow easy access to the following objects:
param: Maps a request parameter name to a single value
paramValues: Maps a request parameter name to an array of values
header: Maps a request header name to a single value
header Values: Maps a request header name to an array of values
cookie: Maps a cookie name to a single cookie
initParam: Maps a context initialization parameter name to a single value
Finally, there are objects that allow access to the various scoped variables described in Using Scope Objects.
page Scope: Maps page-scoped variable names to their values
request Scope: Maps request-scoped variable names to their values
session Scope: Maps session-scoped variable names to their values
application Scope: Maps application-scoped variable names to their values
For instance the below snippet will indentify the browser used by the client.
See the following video on overview and working of Servlets: -
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