JavaWithZ

IMPLICIT OBJECTS- JSP simplifier authoring & provides certain objects implicitly to be accessed within a JSP page without any explicit declaration.
- These objects are called as implicit objects .
- These objects are not declared explicitly but they are provided by Container during translation phase.
There are in all 9 implicit objects

TIP FOR STUDENT:It is always recommended to remember the name of this implicit object & their classes in context to interviews.....
There are 9 implicit objects:-
1) request.
2) response
3) out
4) session
5) application

6) config
7) page
8)pageContext
9)exception

1) request:-
- request object represents all the information about HttpRequest.
- Instance of :javax.servlet.http.HttpServletRequest
- Scope:request scope.- Using this object we can access headers cookies ,etc.

2) response:-
- response object represents response to the client.
- Instance of : javax.servlet.http.HttpServletResponse.
- Scope:page scope- response object is used for adding cookies, redirecting the calls,etc

3) out:-
- out object represents output stream.
- out objects are used for sending arguments to print methods.
- Instance of:javax.servlet.jsp.JSPWriter
-Scope:page scope
4) session:-
- session object is used to track client's information across the session.
- Instance of: javax.servlet.http.HttpSession
- Scope:session scope.

5) application:-
- application object represent the context for the JSP page.
- application object is accessible to any object used within JSP page.
- Instance of:javax.servlet.ServletConfig
- Scope:page scope.

6) config:-
- config object provides access to the initialization parameters
- Instance of : javax.servlet.ServletConfig
- Scope : page scope

7) page:-
- page refers to the instance of JSP implementation class, i.e the JSP itself.
- accessed using 'this' reference.
- Instance of : javax.lang.Object
- Scope:page scope.

8) pageContext:-
- pageContext encapsulates other implicit objects.
- If a class is given pageContext reference it get access to all the objects from all the scope
- Instance of : javax.servlet.jsp.PageContext
- Scope:page scope.
9) exception:-
- Refers to runtime exception that resulted in invoking the errorPage.
- Available only in error page.
- errorPage:- a JSP which has is errorPage attribute true in page directive.
- Instance of :java.lang.Throwable
- Scope:page scope.