package de.rtner.webtools;

import java.io.IOException;
import java.security.Principal;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;

import org.apache.log4j.MDC;

/**
 * Simple Servlet Filter that sets the Log4J MDC to the currently logged-in user.
 * This filter is intended to be used with JBoss´s http-invoker web application
 * to identify/separate parallel fat client RMI requests.
 *
 * $id: $
 *
 * @author Matthias Gärtner
 *
 */
public class MDCUserServletFilter implements Filter
{
    public void init(FilterConfig arg0) throws ServletException
    {
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException
    {
        HttpServletRequest httprequest = (HttpServletRequest) request;
        Principal user = httprequest.getUserPrincipal();

        boolean bUserAdded = false;
        if (user != null)
        {
            String strUser = user.getName();
            if (strUser != null && strUser.length() > 0)
            {
                // Put the principal's name into the message diagnostic
                // context. May be shown using %X{username} in the layout
                // pattern.
                MDC.put("username", strUser);
                bUserAdded = true;
            }
        }

        try
        {
            // Continue processing the rest of the filter chain.
            chain.doFilter(request, response);
        }
        finally
        {
            if (bUserAdded)
            {
                // Remove the added element again - only if added.
                MDC.remove("username");
            }
        }
    }

    public void destroy()
    {
    }
}