RequestDispatcher from servletcontext versus request

Question

What is different between these two code lines and when should we use each of them?

1.

RequestDispatcher view = request.getRequestDispatcher(“result.jsp”);

2.

RequestDispatcher view = getServletContext().getRequestDispatcher(“/result.jsp”);

Answer 1

1) RequestDispatcher view = request.getRequestDispatcher(“result.jsp”);

Here,

• view is relative to the current request. you have to pass relative path of jsp/html
• for chaining two Servlets with in the same web application.

java doc says,

The pathname specified may be relative, although it cannot extend outside the current servlet context. If the path begins with a "/" it is interpreted as relative to the current context root. This method returns null if the servlet container cannot return a RequestDispatcher.

The difference between this method and ServletContext.getRequestDispatcher(java.lang.String) is that this method can take a relative path.

2) RequestDispatcher view = getServletContext().getRequestDispatcher(“/result.jsp”);

Here,

• view is relative to the root of the Servlet context, you have to pass absolute path of jsp/html
• for chaining two web applications with in the same/different servers.

java doc says,

The pathname must begin with a "/" and is interpreted as relative to the current context root. Use getContext to obtain a RequestDispatcher for resources in foreign contexts. This method returns null if the ServletContext cannot return a RequestDispatcher.