Null value in request.getParameter when servlet is called from JSP

Question

I have below a jps with below code with source and destination drop down and a button "Execute" which will call a servlet.

The servet will perform some operation based on the values selected.

JSP Code:

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
    <head>
     <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
        <title/>
    </head>
    <form action="MySourceEnv" method="POST">
        <select name="SourceEnv" >      
            <option>10.100.10.11</option>      
            <option>10.100.10.12</option>      
        </select>   
    </form>
    <form action="MyDestEnv" method="POST">
        <select name="DestEnv" >      
            <option>10.100.10.11</option>      
            <option>10.100.10.12</option>      
        </select>   
    </form>
    <body>
        <button onclick="location.href = 'http://localhost:7500/Project_1/JavaServlet';" id="RedirectButton" > Execute</button>
    </body>
</html>

Servlet Code:

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class JavaServletClass extends HttpServlet {

    public void init() throws ServletException {
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        String SourceEnvParam = request.getParameter("SourceEnv");
        out.println("<h1>" + SourceEnvParam + "</h1>");
        LogicMethod(SourceEnvParam);
    }

    private void LogicMethod(String SourceEnvParam) throws IOException {
        // Some logic here
    }

    public void destroy() {
    }
}

I'm getting the value of request.getParameter("SourceEnv") as Null when execute button is clicked and servlet is called.

What's wrong I'm doing here?

score 3 · Accepted Answer · answered Aug 27 '18 at 07:54

I think problem created in your html code. First of all you created two form out of your body which has two action. But you defined another another action with

<button onclick="location.href = 'http://localhost:7500/Project_1/JavaServlet';" id="RedirectButton" > Execute</button>.

Try writing your jsp page like this

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
    <head>

        <title> name<title/>
    </head>

    <body>
      <form action="JavaServletClass" method="GET">
        <select name="SourceEnv" >      
            <option>10.100.10.11</option>      
            <option>10.100.10.12</option>      
        </select>  
       <select name="DestEnv" >      
            <option>10.100.10.11</option>      
            <option>10.100.10.12</option>      
        </select> 
<button type="submit" value="Submit">Submit</button> 
</form>
</body>
</html>

Null value in request.getParameter when servlet is called from JSP

1 Answers1