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request.getAttribute Not Displaying Anything In JSP

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posted 14 years ago

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Hi everyone,

I have servlet send a request parameter to a JSP, and i am just extracting the values from the request object in the JSP and displaying it. But the values aren't getting printed at all. I debugged the code and i found the request object is coming to the JSP loaded with the values but its not printing anything. Here is my JSP:

Somnath Mallick

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posted 14 years ago

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Well I figured out what the mistake was. Changed the scriptlet tag to expression tag. And its printing the values, except the "percentage" value. Its coming to the jsp into the request object, but somehow its printing null! My updated JSP:

My Servlet:

package com.test.client;

import java.io.IOException;
import java.util.Hashtable;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.test.ejbModules.PercentageBean;
import com.test.ejbModules.PercentageLocal;
import com.test.ejbModules.PercentageRemote;

/**
 * Servlet implementation class SendData
 */
public class SendData extends HttpServlet {
	private static final long serialVersionUID = 1L;

/**
	 * @see HttpServletdoPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
	{
		try 
		{
			String name = request.getParameter("name");
			int rollNo = Integer.parseInt(request.getParameter("rollno"));
			float engScore = Float.parseFloat(request.getParameter("engScore"));
			float hindiScore = Float.parseFloat(request.getParameter("hindiScore"));
			float mathsScore = Float.parseFloat(request.getParameter("mathsScore"));
			float scienceScore = Float.parseFloat(request.getParameter("sciScore"));

Hashtable<String, String> environment = new Hashtable<String, String>();
			environment.put(Context.INITIAL_CONTEXT_FACTORY, "org.jnp.interfaces.NamingContextFactory");
			environment.put(Context.PROVIDER_URL, "jnp://localhost:1099");
			environment.put(Context.URL_PKG_PREFIXES, "org.jboss.naming:org.jnp.interfaces");

PercentageRemote percentageRemote = null;
			Context initial = null;

initial = new InitialContext(environment);
			Object object = initial.lookup("PercentageBean/remote");
			
			percentageRemote = (PercentageRemote) javax.rmi.PortableRemoteObject.narrow(object, PercentageRemote.class);

float percentage = percentageRemote.getPercentage(engScore, hindiScore, mathsScore, scienceScore);

request.setAttribute("name", name);
			request.setAttribute("rollno", rollNo);
			request.setAttribute("percentage", percentage);
			RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/jsp/showData.jsp");
			dispatcher.forward(request,response);
		} 
		catch(NamingException e) 
		{
			e.printStackTrace();
		} 
	}
}

Could you tell me how come my two values are getting printed and not the third???

David Newton

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You're printing parameters, but setting attributes.

Somnath Mallick

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Got it! Thanks Dave!

David Newton

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No problem; glad I could help :)

Bear Bibeault

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Scriptlets? In 2010? Is this legacy code? If not, it's high time to update your JSP knowledge.

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Somnath Mallick

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Its just something i tried out. Actually my main intention was to learn calling an EJB from a servlet and displaying the result in an JSP. I hardly use JSP's. If the JSP specification and all have changed a lot, i would be glad to look into it. Please give me some details...

David Newton

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JSP 2.0. JSP EL.

Somnath Mallick

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Ok. Thanks all! I'll look into it!

Somnath Mallick

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I looked at some of documents in Google and found out that JSP 2.0 makes extensive use EL, which comes from JSTL. Now, i have never used JSTL, so would i be able to learn JSP 2.0 without knowing JSTL 1.0? Or should i go through JSTL as well before digging into JSP 2.0?

Bear Bibeault

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Somnath Mallick wrote:... EL, which comes from JSTL.

That is not correct. As of JSP 2.0, the EL is evaluated by the core JSP engine and is independent of the JSTL.

Now, i have never used JSTL, so would i be able to learn JSP 2.0 without knowing JSTL 1.0?

JSTL 1.0 is for JSP 1.2. If you are using JSP 2.x, you should be using JSTL 1.1 or 1.2.

And without the JSTL, you'll need to resort to using scriptlets in your pages to do pretty much anything. Bad idea. Very bad idea. Man up and learn JSTL and step into the modern world of JSP.

Or should i go through JSTL as well before digging into JSP 2.0?

Learn the JSP 2.0 EL and JSTL in conjunction with each other. They go together like hand and glove.

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Somnath Mallick

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Ok. Thanks!! I will start with JSTL 1.2 then!

Bear Bibeault

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The JSTL Specification is easy to read. I'd suggest using it for your research.

The EL Specification is a little tricky. It's polluted with stuff for JSF that doesn't apply to JSP, so you have to be careful not to get confused.

Be sure that any material you use does not focus on JSP scriptlets. They're outdated and replaced by the JSTL and EL.

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