Passing transfer from servlet to JSP

[Abhishek Asthana]

Hi,
I am really going to die or atleast become insane if this thing doesn't get sort out soon and I am not joking!
I am facing a strange problem. I have written a servlet and I am sending some data from servlet to a JSP.

This is the code for Servlet:

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

When I call this servlet in browser I get this:

 
22:31:10,240 ERROR [STDERR] java.lang.NullPointerException
22:31:10,240 ERROR [STDERR] at shopping.onlinestore.client.OnlineStoreServlet.doGet(OnlineStoreServlet.java:73)
22:31:10,240 ERROR [STDERR] at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
22:31:10,240 ERROR [STDERR] at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
22:31:10,240 ERROR [STDERR] at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:360)
22:31:10,240 ERROR [STDERR] at org.mortbay.jetty.servlet.WebApplicationHandler.dispatch(WebApplicationHandler.java:294)
22:31:10,240 ERROR [STDERR] at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:558)
22:31:10,240 ERROR [STDERR] at org.mortbay.http.HttpContext.handle(HttpContext.java:1714)
22:31:10,240 ERROR [STDERR] at org.mortbay.jetty.servlet.WebApplicationContext.handle(WebApplicationContext.java:507)
22:31:10,240 ERROR [STDERR] at org.mortbay.http.HttpContext.handle(HttpContext.java:1664)
22:31:10,240 ERROR [STDERR] at org.mortbay.http.HttpServer.service(HttpServer.java:863)
22:31:10,240 ERROR [STDERR] at org.jboss.jetty.Jetty.service(Jetty.java:460)
22:31:10,240 ERROR [STDERR] at org.mortbay.http.HttpConnection.service(HttpConnection.java:775)
22:31:10,240 ERROR [STDERR] at org.mortbay.http.HttpConnection.handleNext(HttpConnection.java:939)
22:31:10,240 ERROR [STDERR] at org.mortbay.http.HttpConnection.handle(HttpConnection.java:792)
22:31:10,240 ERROR [STDERR] at org.mortbay.http.SocketListener.handleConnection(SocketListener.java:201)
22:31:10,240 ERROR [STDERR] at org.mortbay.util.ThreadedServer.handle(ThreadedServer.java:289)
22:31:10,240 ERROR [STDERR] at org.mortbay.util.ThreadPool$PoolThread.run(ThreadPool.java:455)
 
 

But when I call http://127.0.0.1/OnlineStore/OnlineStore.jsp in browser I get the right page, with the data the servlet is supposed to pass to it. What can be the reason?
I even used :

response.sendRedirect("/OnlineStore.jsp");

so the code becomes :

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

but this too doesn't help.
Please help me!!!
Thanks. I will pray to God for your health and prosperity!
Abhishek.

[Hari Gangadharan]

Can you tell me what is in line 73 of OnlineStoreServlet.java??

[ramprasad madathil]

I am really going to die or atleast become insane if this thing doesn't get sort out soon and I am not joking!

well, dont. we shall try and help

Given that
1.the page is loading with the correct data
2. the final url is /OnlineStore/OnlineStore.jsp
,it looks like the request is getting forwarded correctly,

so tell us what's in line number 73 below
shopping.onlinestore.client.OnlineStoreServlet.doGet(OnlineStoreServlet.java:73) ?

why do you think the null pointer exception occured at the code you have posted?

ram.

[Abhishek Asthana]

Thanks for consoling!
Line 73 is:

 rd.forward(request,response); 

Frankly I don't have any idea why is rd null. And since data is being displayed correctly in JSP,this is intriguing why the JSP page doesn't show up on its own.
Abhishek.

[Ben Souther]

Without seeing all of your code, it's hard to guess what the problem is.
It is generally a good practice to return right after forwarding or redirecting. Neither halts the excecution of your servlet.

Also, don't try to forward AND redirect. Do one or the other.

try{
    HttpSession session=request.getSession(true);
    session.setAttribute("ResultsList",resultsList);
    RequestDispatcher rd = request.getRequestDispatcher("/OnlineStore.jsp");
    rd.forward(request,response);
    [B]return;[/B]
}catch(Exception e){
    System.out.println("error2 in doGet "+ e);
    e.printStackTrace();
    out.println("error2 in doGet "+e);
}

[Abhishek Asthana]

Hi,
Perhaps God listened to me or some miracle happened, or it were your wishes!!!
This is the code that is working:

try
{
HttpSession session=request.getSession(true);
session.setAttribute("ResultsList",resultsList);
RequestDispatcher rd=request.getRequestDispatcher("/OnlineStore.jsp");
rd.forward(request,response);
}
catch(Exception e)
{
System.out.println("error in addToCart "+ e);
e.printStackTrace();
}

Can you find any difference between this code and the original one? I can't and I am surprised, why it is working now!
But whatever thanks a lot to all of you, you really helped me.
Thanks once again.
Abhishek

[Nilesh Srivastava]

Hi All,

I am facing the same thing. And unfortunately my problem is still LIVE !!. Actually I ahve a JSP page with some input fields.I am posting the page and data is passed on to servlets.Along with these input data, I have one vector as well which I need to pass on to servlet, so I did

request.setAttribute("vecName",vecData);

But when I am recieveing the same vector in Servlet with :

Vector vecSerData = (Vector)request.getAttribute("vecName");

It is giving me "null". And I am getting NULL POINTER EXCEPTION.

The vector is not null in jSP. When I say System.out.println(vecData);
it prints something. But when I say same thing in Servlet .. it prints null.

Can any one tell me WHY??

Thanks in advance..

[Nilesh Srivastava]

Hi All,

I am facing the same thing. And unfortunately my problem is still LIVE !!. Actually I ahve a JSP page with some input fields.I am posting the page and data is passed on to servlets.Along with these input data, I have one vector as well which I need to pass on to servlet, so I did

request.setAttribute("vecName",vecData);

But when I am recieveing the same vector in Servlet with :

Vector vecSerData = (Vector)request.getAttribute("vecName");

It is giving me "null". And I am getting NULL POINTER EXCEPTION.

The vector is not null in jSP. When I say System.out.println(vecData);
it prints something. But when I say same thing in Servlet .. it prints null.

Can any one tell me WHY??

Thanks in advance..

[Ben Souther]

When you say "input fields" do you mean HTML form fields, '<inpu type=text...'?

If so, the reason why is that, once the data is written to the user's browser, that request is over and gone. When the user submits the form, a NEW request has begun and that new request isn't going to have the attributes of the last one.

If you need your vector to survive across requests, you will need to store it in session scope.
[ March 23, 2005: Message edited by: Ben Souther ]