Getting null on sending values from Servlet to Client-side JSP

Question

I am trying a simple example of sending values from a servlet Servlet1.java to client-side JSP page client1.jsp.

But I am getting null Here is the code Server1.java:

import java.io.*;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.util.*;


@WebServlet("/server1")
public class Server1 extends HttpServlet {
private static final long serialVersionUID = 1L;

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
{

    String name="Rahul";
    request.setAttribute("myname",name);

    //Servlet JSP communication
    RequestDispatcher reqDispatcher = getServletConfig().getServletContext().getRequestDispatcher("/client1.jsp");
    reqDispatcher.forward(request,response);

}
}

Code for client1.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
 <!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <% String s=request.getParameter("myname");%>
    Hello friends <%=s%>
</body>
</html>

You are setting an attribute and getting a parameter. Try getting the attribute in your jsp instead. — DanielBarbarian, Aug 10 '18 at 08:39
So you are using `request.getAttribute("myname")` but that is still null? Are you doing a post request to your servlet? — DanielBarbarian, Aug 10 '18 at 08:50
Are you getting `Hello friends null` or are you getting a `NullPointerException`? — DanielBarbarian, Aug 10 '18 at 08:52
And you are sure you are doing a POST request to that servlet and not going directly to the jsp page in your browser? — DanielBarbarian, Aug 10 '18 at 08:56
In other words, what url are you using when you are testing this? — DanielBarbarian, Aug 10 '18 at 09:04
Sorry I don't know much I can't understand you can refer the code please. — Rahul Choubey, Aug 10 '18 at 09:05
try `localhost:8080/mypro/server1`. Oh and change `doPost` in your servlet code to `doGet`. — DanielBarbarian, Aug 10 '18 at 09:09

Serge Ballesta · Accepted Answer · 2018-08-10T08:59:06.000

2

What you do is bad.

First you are mixing attributes and parameters. They are different animals. Parameters is what comes from the client and are set once by the servlet container. Attributes are objects that are used by cooperating elements (filters, servlets and JSP pages) for passing data.

So you should at least read the attributes in JSP:

<% String (String) s=request.getAttribute("myname");%>

You must cast the attribute to String because getAttribute returns an Object.

But that's not all. Scriptlets are deprecated for decades, and should only be used for very special use cases, if any. Here, assuming you have a decent servlet container, you could simply use the ${} JSTL automatic attribute:

<body>
    Hello friends ${myname}
</body>

It is shorter, cleaner and less error prone.

After your comments, there is another possible problem. You only show the override of doPost in your servlet code, when common requests (unless you post from a form) are GET requests and are processed in doGet. If you use a GET request and only set the attribute in doPost your JSP will not find it...

edited Aug 10 '18 at 08:59

answered Aug 10 '18 at 08:53

Serge Ballesta

143,923
11
122
252

Now it is not showing null but also it is not showing value of that string. – Rahul Choubey Aug 10 '18 at 09:03
It worked ! I wrote the code in doGet ,changed to getAttribute and thanks for other tips as well – Rahul Choubey Aug 10 '18 at 09:51
But It showed only on server page I want it on client page .What should I do? – Rahul Choubey Aug 10 '18 at 11:23
@RahulChoubey: I'm sorry by I can't understand. What do you mean by client page? A JSP is translated by the server container in a true servlet, so it can only exists inside a server side web application – Serge Ballesta Aug 10 '18 at 12:04

score 1 · Answer 2 · answered Aug 10 '18 at 08:49

1

"myname" you are setting to request.setAttribute

so, you can retrieve as below:

<% String s=(String) request.getAttribute("myname");%>

answered Aug 10 '18 at 08:49

Durga Prasad

81
1
9

Still getting null – Rahul Choubey Aug 10 '18 at 08:51

Getting null on sending values from Servlet to Client-side JSP

2 Answers2