ServletContext.getRequestDispatcher() vs ServletRequest.getRequestDispatcher()

Question

why

getRequestDispatcher(String path) of the ServletRequest interface cannot extend outside the current servlet context

where as

getRequestDispatcher(String path) of the ServletContext can use the getContext(String uripath) method to obtain RequestDispatcher for resources in foreign contexts.

and how??

Please help

Answer 1

If you use an absolute path such as ("/index.jsp"), there is no difference.

If you use relative path, you must use HttpServletRequest.getRequestDispatcher(). ServletContext.getRequestDispatcher() doesn't allow it.

For example, if you receive your request on http://example.com/myapp/subdir,

    RequestDispatcher dispatcher =          request.getRequestDispatcher("index.jsp");     dispatcher.forward( request, response );  

Will forward the request to the page http://example.com/myapp/subdir/index.jsp.

In any case, you can't forward request to a resource outside of the context.

Answer 2

The request method getRequestDispatcher() can be used for referring to local servlets within single webapp.

Servlet context based getRequestDispatcher() method can used of referring servlets from other web applications deployed on SAME server.