/**
    * Logback: the reliable, generic, fast and flexible logging framework.
    * Copyright (C) 1999-2011, QOS.ch. All rights reserved.
    *
    * This program and the accompanying materials are dual-licensed under
    * either the terms of the Eclipse Public License v1.0 as published by
    * the Eclipse Foundation
    *
    *   or (per the licensee's choosing)
   *
   * under the terms of the GNU Lesser General Public License version 2.1
   * as published by the Free Software Foundation.
   */
  package ch.qos.logback.classic.selector.servlet;
  
  import java.io.IOException;
  
  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 org.slf4j.LoggerFactory;
  
  import ch.qos.logback.classic.LoggerContext;
  import ch.qos.logback.classic.selector.ContextJNDISelector;
  import ch.qos.logback.classic.selector.ContextSelector;
  import ch.qos.logback.classic.util.ContextSelectorStaticBinder;
  
  /**
   * A servlet filter that puts the environment dependent LoggerContext in a
   * ThreadLocal variable, removing it after the request is processed.
   * 
   * <p>To use it, add the following lines to a web.xml file
   *  
   * <filter>
   *   <filter-name>LoggerContextFilter</filter-name>
   *   <filter-class>
   *     ch.qos.logback.classic.selector.servlet.LoggerContextFilter
   *   </filter-class>
   * </filter>
   * <filter-mapping>
   *   <filter-name>LoggerContextFilter</filter-name>
   *   <url-pattern>/*</url-pattern>
   * </filter-mapping>
   * 
   * @author S&eacute;bastien Pennec
   */
  public class LoggerContextFilter implements Filter {
  
    public void destroy() {
      //do nothing
    }
  
    public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain chain) throws IOException, ServletException {
  
      LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
      ContextSelector selector = ContextSelectorStaticBinder.getSingleton().getContextSelector();
      ContextJNDISelector sel = null;
  
      if (selector instanceof ContextJNDISelector) {
        sel = (ContextJNDISelector)selector;
        sel.setLocalContext(lc);
      }
  
      try {
        chain.doFilter(request, response);
      } finally {
        if (sel != null) {
          sel.removeLocalContext();
        }
      }
    }
  
    public void init(FilterConfig arg0) throws ServletException {
      //do nothing
    }
  }