001/**
002 * Logback: the reliable, generic, fast and flexible logging framework.
003 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
004 *
005 * This program and the accompanying materials are dual-licensed under
006 * either the terms of the Eclipse Public License v1.0 as published by
007 * the Eclipse Foundation
008 *
009 *   or (per the licensee's choosing)
010 *
011 * under the terms of the GNU Lesser General Public License version 2.1
012 * as published by the Free Software Foundation.
013 */
014package chapters.mdc;
015
016import java.io.IOException;
017import java.security.Principal;
018
019import jakarta.servlet.Filter;
020import jakarta.servlet.FilterChain;
021import jakarta.servlet.FilterConfig;
022import jakarta.servlet.ServletException;
023import jakarta.servlet.ServletRequest;
024import jakarta.servlet.ServletResponse;
025import jakarta.servlet.http.HttpServletRequest;
026
027import org.slf4j.MDC;
028
029/**
030 * A simple servlet filter that puts the username
031 * found either in the Principal.
032 * 
033 * <p> The value is removed from the MDC once the request has been
034 * fully processed.
035 *
036 * @author S&eacute;bastien Pennec
037 */
038public class UserServletFilter implements Filter {
039
040    private final String USER_KEY = "username";
041
042    public void destroy() {
043    }
044
045    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
046
047        boolean successfulRegistration = false;
048        HttpServletRequest req = (HttpServletRequest) request;
049        Principal principal = req.getUserPrincipal();
050        // Please note that we also could have used a cookie to
051        // retrieve the user name
052
053        if (principal != null) {
054            String username = principal.getName();
055            successfulRegistration = registerUsername(username);
056        }
057
058        try {
059            chain.doFilter(request, response);
060        } finally {
061            if (successfulRegistration) {
062                MDC.remove(USER_KEY);
063            }
064        }
065    }
066
067    public void init(FilterConfig arg0) throws ServletException {
068    }
069
070    /**
071     * Register the user in the MDC under USER_KEY.
072     * 
073     * @param username
074     * @return true id the user can be successfully registered
075     */
076    private boolean registerUsername(String username) {
077        if (username != null && username.trim().length() > 0) {
078            MDC.put(USER_KEY, username);
079            return true;
080        }
081        return false;
082    }
083
084}