URL rewriting

I have some doubts in URL rewriting.
I have made servlet UrlRewrite.java where I m using encodeURL() and then going to
Page Hi.jsp.
When clicked on link, I got Hi.jsp page and jsession id appended to the url.
Then I clicked on link & went to bye.jsp
But this time I go the output as "session is new" .

Question :
1)Is it necessary to use response.encodeURL() everytime when you are navigating form one page to another using <a href=""></a> tags. ?
2)when I use requestDispatcher from Hi.jsp to Bye.jsp.then i got output "session is not new", WHY ?

NOTE : I have disabled browser cookies.

Here is code.
1) UrlRewrite.java
import javax.servlet.ServletException;
import javax.servlet.http.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class UrlRewrite extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, java.io.IOException {
response.setContentType("text/html");
java.io.PrintWriter out = response.getWriter();
String contextPath = request.getContextPath();
HttpSession hs=request.getSession();

String encodedUrl = response.encodeURL(contextPath+"/Hi.jsp");
System.out.println(encodedUrl);
out.println("<html>");
out.println("<head>");
out.println("<title>URL Rewriter</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>This page will use URL rewriting if necessary</h2>");
out.println("Go to the Hi.jsp page <a href=\"" + encodedUrl+ "\">here</a>.");
//out.println("Go to the Hi.jsp page <a href=\"/Hi.jsp\">here</a>.");
out.println("</body>");
out.println("</html>");
}

}

2)Hi.jsp
<%@page contentType="text/html" session="true" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">

<h2>Hello World!</h2>
</body>
</html>
<%
String str=request.getContextPath()+"/Bye.jsp";
out.println(str);
%>
<a href ="<%=encodeURL%>">Bye</a>

3)Bye.jsp
<%@page contentType="text/html" session="true" pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>JSP Page</title>
</head>
<body>
<%
HttpSession hs=request.getSession();

if (hs.isNew())
{
out.println("session is new");
}
else
{
out.println("session is not new");
String id=hs.getId();
out.println(id);
}

%>
<h2>Bye World!</h2>
</body>
</html>

Thanks in advance.
manish

1. Yes
2. because session is not chnaged as you move from Hi.jsp to Bye.jsp

By the way , your Hi.jsp code is wrong. correct code is

<%@page contentType="text/html" session="true" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">

Thank You