Why the getAtrribute() returns the null value in servlet?

Question

In the following code i am trying to get the name from client and set in the session but there getAtrribute("unm") returning the null value...

    res.setContentType("text/html");
    PrintWriter op=res.getWriter();
    HttpSession ss=req.getSession(true);

    String sunm=(String)req.getAttribute("unm");

    System.out.println(sunm);
    ss.setAttribute("UserName", sunm);  
    op.println("<br><center>The user for this session is :"+sunm+"</center>");

please help me...

score 0 · Accepted Answer · edited May 23 '17 at 10:31

0

Use getParameter() method instead of getAttribute(), getAttribute() is for only server side.

res.setContentType("text/html");
PrintWriter op=res.getWriter();
HttpSession ss=req.getSession(true);

String sunm=(String)req.getParameter("unm");

System.out.println(sunm);
ss.setAttribute("UserName", sunm);  
op.println("<br><center>The user for this session is :"+sunm+"</center>");

For reference: Difference between getAttribute() and getParameter()

edited May 23 '17 at 10:31

Community

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answered Oct 13 '13 at 08:58

Ramesh Kotha

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It working.. but as normal getParameter value it not set as session. – Shivaji More Oct 13 '13 at 09:08

score 0 · Answer 2 · answered Oct 15 '13 at 19:41

The problem you are having is that you are getting a session attribute that hasn't been set.So you would have to get the parameter in which the name of the client is inputted,then you can set the session attribute based on the parameter that is being retrieved. In code terms,in order to get the parameter you use the getParameter() method.

 res.setContentType("text/html");
  PrintWriter op = res.getWriter();
  HttpSession ss= req.getSession(true);

  String sunm = (String)req.getParameter("unm");
  System.out.println(sunm);

and then set the session attribute based on the variable sunm

ss.setAttribute("Username",sunm);
op.println("<br><center>The user for this session is:"+sunm+"</center>");

You can read the reference that Ramesh K added to better understand the difference between getAttribute() and getParameter().

Why the getAtrribute() returns the null value in servlet?

2 Answers2