What are Implicit Objects in JSP?
Implicit Objects in JSP are those objects which are created/instantiated implicitly by the JSP Engine (part of the underlying Web Container) as a convenience feature for the JSP page writers who can use them without having to instantiate them. These implicit objects implement the interfaces defined in the JSP/Servlet APIs. There are nine implicit objects in JSP, which are:-
interface which is used for requesting a web resource - dynamic or static. This implicit object has a 'request' scope.
An important point to note here is that all these Container supplied implicit objects are accessible only in the Container generated _jspService() method and not in any user defined method of the JSP page.
Update[June 24, 2008]: Read more - Error/Exception Handling in JSP>> for understanding how the implcit object 'exception' is built, passed, accessed, and used by using several error handling mechanisms available for JSPs.