What is the difference between the getRequestDispatcher(String) and getNamedDispatcher(String) methods in the ServletContext Class?

NamedDispatcher

Returns a RequestDispatcher object that acts as a wrapper for the named servlet.

getNamedDispatcher(String) method takes the name of the Servlet as parameter which is declared via Deployment descriptor.

Example: Deployment Descriptor


<servlet>
    <servlet-name>FirstServlet</servlet-name>
    <servlet-class>com.example.ServletExample</servlet-class>
</servlet>


 RequestDispatcher dispatch = request.getNamedDispatcher(?FirstServlet??);

dispatch.forward(request, response);

Note: A servlet instance can determine its name using servletConfig.getServletName(); This method returns the name of the class that implements the Servlet interface or extends the HttpServlet class.

RequestDispatcher

Returns a RequestDispatcher object that acts as a wrapper for the resource located at the given path.

 RequestDispatcher dispatch = request.getRequestDispatcher("/tes");

Here "/tes" represents the url-pattern element value of the servlet class.


<servlet-mapping>
    <servlet-name>Test</servlet-name>
    <url-pattern>/tes</url-pattern>
</servlet-mapping>


It represents the path of the servlet class. Since both the base as well as target servlet are in the same package structure by just specifying the url-pattern element value we will be able to access the target servlet.

We shouldn't specify the entire path like

 String str = "/WEB-INF/classes/com/example/posr/Test"

 RequestDispatcher dispatch = request.getRequestDispatcher(str);

To forward a request to a JSP page we use

 RequestDispatcher dispatch = request.getRequestDispatcher("/TestJspOne.jsp");

Here "/TestJspOne.jsp" the slash denotes the Jsp page is at the root of the application.