Using RequestDispatcher, NullPointerException

[Abhishek Asthana]

Hi,
I am using RequestDispatcher to forward data from servlet to JSP.

  
try{
HttpSession session=request.getSession(true);
session.setAttribute("LoginMessage",loginMessage);
RequestDispatcher rd=request.getRequestDispatcher("../LoginMessage.jsp");
rd.forward(request,response);
}catch(Exception e){
System.out.println("error2 in doGet "+e);
e.printStackTrace();
out.println("error2 in doGet");

I am working in JBoss 3.2.1, When I run the servlet in browser I get this error:

  
21:02:02,013 INFO  [STDOUT] error2 in doGet java.lang.NullPointerException
21:02:02,013 ERROR [STDERR] java.lang.NullPointerException
21:02:02,013 ERROR [STDERR] at au.com.tusc.servlet.MyServlet.doPost(MyServlet.java:69)
21:02:02,013 ERROR [STDERR] at au.com.tusc.servlet.MyServlet.doGet(MyServlet.java:80)
21:02:02,013 ERROR [STDERR] at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
21:02:02,013 ERROR [STDERR] at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
21:02:02,013 ERROR [STDERR] at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:360)
21:02:02,013 ERROR [STDERR] at org.mortbay.jetty.servlet.WebApplicationHandler.dispatch(WebApplicationHandler.java:294)
21:02:02,013 ERROR [STDERR] at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:558)
21:02:02,013 ERROR [STDERR] at org.mortbay.http.HttpContext.handle(HttpContext.java:1714)
21:02:02,013 ERROR [STDERR] at org.mortbay.jetty.servlet.WebApplicationContext.handle(WebApplicationContext.java:507)
21:02:02,013 ERROR [STDERR] at org.mortbay.http.HttpContext.handle(HttpContext.java:1664)
21:02:02,013 ERROR [STDERR] at org.mortbay.http.HttpServer.service(HttpServer.java:863)
21:02:02,013 ERROR [STDERR] at org.jboss.jetty.Jetty.service(Jetty.java:460)
21:02:02,013 ERROR [STDERR] at org.mortbay.http.HttpConnection.service(HttpConnection.java:775)
21:02:02,013 ERROR [STDERR] at org.mortbay.http.HttpConnection.handleNext(HttpConnection.java:939)
21:02:02,013 ERROR [STDERR] at org.mortbay.http.HttpConnection.handle(HttpConnection.java:792)
21:02:02,013 ERROR [STDERR] at org.mortbay.http.SocketListener.handleConnection(SocketListener.java:201)
21:02:02,013 ERROR [STDERR] at org.mortbay.util.ThreadedServer.handle(ThreadedServer.java:289)
21:02:02,013 ERROR [STDERR] at org.mortbay.util.ThreadPool$PoolThread.run(ThreadPool.java:455)
 

What may be the problem? why is rd null? Please help.
Thanks,
Abhishek

[Durga Prasanna Kar]

You have to add the code as:
getServletContext().getRequestDispatcher(".....path.....");
Try this instead of request.something.

[ramprasad madathil]

You have to add the code as:
getServletContext().getRequestDispatcher(".....path.....");
Try this instead of request.something.

You could obtain the RequestDispatcher object using the request object too.
Thus

  
  RequestDispatcher rd = request.getRequestDispatcher(path to resource) 

is correct.

The problem in the original poster's code is that he has used Windows style path locator (../resource) to locate the jsp.

This is what the api has to say

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.

Thus to locate a jsp resource under the WEB-INF folder, use

  
  RequestDispatcher rd = request.getRequestDispatcher("/<fileName>.jsp") 
  //RequestDispatcher rd = getServletContext().getRequestDispatcher(path to resource) is also correct

If your jsp is registered as a servlet, you could also use the getNamedDispatcher() method of ServletContext

  
  RequestDispatcher rd = getServletContext().getNamedDispatcher("ServletName");

ram.

[Adeel Ansari]

Originally posted by Durga Prasanna Kar:
You have to add the code as:
getServletContext().getRequestDispatcher(".....path.....");
Try this instead of request.something.

Better do this.

getServletContext().getRequestDispatcher("/<path>/<page>");

Note: it must begin with a "/".

As said earlier that we can get RequestDispatcher object using request object too. And if we go to the point.

RequestDispatcher rd=request.getRequestDispatcher("LoginMessage.jsp");
// it would work

[ March 02, 2005: Message edited by: Adeel Ansari ]