my actionform is not populated

[thri nath]

my action form is not populated because of that I am getting and error as nullpointer exception.so how can i populate my action form.here my code of struts-config.xml,actionclassand action form.
---------------------------------------------------------------------------
struts-config.xml:
..................

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE struts-config PUBLIC
          "-//Apache Software Foundation//DTD Struts Configuration 1.1//EN"
          "http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd">
<struts-config>
<form-beans>
<form-bean name="MyBean" type="login.MyActionForm"/>
</form-beans>
<action-mappings>
<action type="login.MyAction" name="MyBean" path="/login" validate="false">
<forward name="valid"  path="/Valid.jsp"/>
<forward name="invalid" path="/invalid.jsp"/>
</action>
</action-mappings>
</struts-config>

---------------------------------------------------------------------------
ACTIONCLASS:
............

package login;
import login.ValueObject;
import login.MyActionForm;
import javax.servlet.http.*;
import org.apache.struts.action.*;
public class MyAction extends Action
{
public ActionForward execute(ActionMapping am,ActionForm af,HttpServletRequest req,HttpServletResponse res) throws Exception
{
         System.out.println("this is action class");
 MyActionForm maf=(MyActionForm)af;
 ValueObject vo=new ValueObject();
 System.out.println("this is action "+(String)maf.getUserId());
 vo.setUserId(maf.getUserId());
 vo.setUserPwd(maf.getUserPwd());
 LoginBusinessDeligate lbd=new LoginBusinessDeligate();
 if(lbd.validateUser(vo))
 return am.findForward("valid");
 else
 return am.findForward("invalid");

}
} 

---------------------------------------------------------------------------
ACTIONFORM:

...........
package login;
import org.apache.struts.action.*;
public class MyActionForm extends ActionForm
{
public void setUserId(String s)
{
UserId=s;
System.out.println("this action form"+UserId+","+s);
}
public String getUserId()
{
return UserId;
}
public void setUserPwd(String s)
{
UserPwd=s;
}
public String getUserPwd()
{
return UserPwd;
}
private String UserPwd,UserId;
}

[BSouther: Added UBB CODE tags]
[ March 17, 2007: Message edited by: Ben Souther ]

[Jeanne Boyarsky]

Thri,
Can you show the JSP/HTML that submits to this form?

[Kevin Liu]

How about your web.xml ??

[Kevin Liu]

and .jsp file

[Brent Sterling]

What line of code is throwing the NullPointerException? What object is null?

- Brent