Passing a variable from JSP to Java

Question

I am trying to pass a string variable called seq from a JSP to a Java program, and pass it on to the another Java program by passing the string as an argument to its object. I am somehow getting stuck.

Start.jsp:

<%@ page import="org.dypbbi.nirmiti.ProtModMain %>
<%@ 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>NIRMITI</title>
    </head>
    <body>
        <h1>Please wait...</h1>
        <%
            String seq=request.getParameter("s");
            ProtModMain.getSequence(seq);
        %>
    </body>
</html>

ProtModMain.java:

package org.dypbbi.nirmiti;
public class ProtModMain {
    String sequence="";

    public static String getSequence(String str)
    {
        return str;
    }


    public static void main(String args[])throws Exception
    {
      ProtModMain MainObj = new ProtModMain();
      sequence = MainObj.getSequence();
      new ObjectFactory(sequence);
    }
}

Start.jsp will retrieve the string value from the HTML. It passes the string to ProtModMain class via the method getSequence. I now need to use the string value to pass it to other classes that require it, so I intend to pass it a parameter to the ObjectFactory object. But before that, I need to call the getSequence method in the ProtModMain class so that I can pass the value. I am not understanding how to call the getSequence method in the main method of ProtModMain class.

You have a misconception of how jsps work and how they should be used. Take a look at the wiki for both jsp and servlets — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Apr 15, 2013 at 18:28

Sujay · Accepted Answer · 2022-11-03 11:27:41Z

1

You need to set the parameter to the request using request.setAttribute("<name>",<value>). Then you can get it in the Java file using request.getAttribute("<name>").

Reference - Oracle Docs - HttpServletRequest

edited Nov 3, 2022 at 11:27

answered Apr 17, 2013 at 12:04

Sujay

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2 Comments

user7436930 Over a year ago

request has no "setParameter" method

Sujay Over a year ago

Referring to the oracle docs link the right way is to use getAttribute and setAttribute methods. request.setAttribute("<name>",<value>) and request.getAttribute("<name>") Correcting Answer.

Fernando M. Pinheiro · Accepted Answer · 2013-04-16 00:35:48Z

0

You are not calling the main method. In your JSP you are calling only the static getSequence that, by the way, only returns the value.

I think you have a project concept problem: why your web (JSP) app has a main class?

I think you should adapt:

Start.jsp:

<%@ page import="org.dypbbi.nirmiti.ProtModMain %> 
<%@ 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>NIRMITI</title>
    </head>
    <body>
        <h1>Please wait...</h1>
        <%
        String seq=request.getParameter("s");
        ProtModMain protModMain = new ProtModMain();
        ObjectFactory myFactory = protModMain.createFactory(seq);
        //do whatever you want with your factory ;)
        %>
    </body>
</html>

ProtModMain.java:

package org.dypbbi.nirmiti;
public class ProtModMain {

    public ObjectFactory createFactory(final String sequence) {
        return new ObjectFactory(sequence);
    }
}

This way you will be calling the methods you intended to.

edited Apr 16, 2013 at 0:35

answered Apr 15, 2013 at 18:31

Fernando M. Pinheiro

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2 Comments

kuks Over a year ago

Thanks. I was thinking, what if I avoid the ProtModMain.java class all together. I can pass the value directly to the ObjectFactory class and avoid the middle man, right? String seq=request.getParameter("s"); new ObjectFactory(seq); the ObjectFactory class will directly receive the string value. This will work right?

Fernando M. Pinheiro Over a year ago

@kuks Yes, will work and, if you are only instantiating ProdModMain to get a ObjectFactory instance, I think that it is much more clean to get to the ObjectFactory directly. You could avoid even the variable: new ObjectFactory(request.getParameters("s"));

Dave Newton · Accepted Answer · 2013-04-16 00:47:03Z

0

You can use <form> tags and <input type='hidden'> with an <input type='submit'> button, in the form you will specify the method to send and to where send the data.

Or you can store in POJOs and store in session and recover it with a servlet.

Or use Ajax with an XmlHttpRequest.

edited Apr 16, 2013 at 0:47

Dave Newton

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answered Apr 15, 2013 at 18:28

elopez

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