filter question

[Scott Purcell]

Hello,
I am having trouble with a filter. Code below.
 
What I am trying to achieve is as follows: We have a current web-site, with a 
lot of jsp pages, etc. We are moving the code to a load-balanced environment, 
and I would like to put a hidden "IP" address into each display page. This way 
I can know which environment the page came from when debugging, etc.
 
I figured I could use a 'filter' and have each page insert the IP into itself 
in a hidden field. I am unable to achieve my goal and could use a hand if 
anyone has experience with this. Is this possible, or will I have to write into 
a header and then edit each jsp page to show the value?
 
 
 
Here is what I have, but it does not print anything on pages.
 
web.xml
<filter>
   <filter-name>HelloWorld</filter-name>
   <filter-class>chapter18.HelloWorldFilter</filter-class>
  </filter>
 
  <filter-mapping>
   <filter-name>HelloWorld</filter-name>
   <url-pattern>/*.jsp</url-pattern>
  </filter-mapping>
 
And I have the servlet code from SCWCD book
package chapter18;
 
import java.io.*;
import javax.servlet.*;
 

public class HelloWorldFilter
    implements Filter
{
 
    public void destroy()
    {
    }
 
    public void doFilter(ServletRequest servletrequest, ServletResponse 
servletresponse, FilterChain filterchain)
        throws ServletException, IOException
    {
        PrintWriter printwriter = servletresponse.getWriter();
        printwriter.println("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX");
    }
 
    public void init(FilterConfig filterconfig)
    {
        filterConfig = filterconfig;
        System.out.println("Chapter 18: HelloWorldFilter initialized");
    }
 
    public HelloWorldFilter()
    {
    }
 
    private FilterConfig filterConfig;
}
 
 
Thanks,
Scott