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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements. See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache license, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License. You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the license for the specific language governing permissions and
    15   * limitations under the license.
    16   */
    17  package org.apache.logging.log4j.web;
    18
    19  import java.io.IOException;
    20  import javax.servlet.Filter;
    21  import javax.servlet.FilterChain;
    22  import javax.servlet.FilterConfig;
    23  import javax.servlet.ServletContext;
    24  import javax.servlet.ServletException;
    25  import javax.servlet.ServletRequest;
    26  import javax.servlet.ServletResponse;
    27
    28  import org.apache.logging.log4j.Logger;
    29  import org.apache.logging.log4j.status.StatusLogger;
    30
    31  /**
    32   * This is responsible for the following:
    33   * <ul>
    34   *     <li>Clearing the logger context when the application has finished starting up.</li>
    35   *     <li>Setting the logger context before processing a request and clearing it after processing a request.</li>
    36   *     <li>Setting the logger context when the application is starting to shut down.</li>
    37   * </ul>
    38   * This filter is a once-per-request filter. It is capable of filtering all the different types of requests
    39   * (standard, asynchronous, error, etc.) but will not apply processing if the filter matches multiple times on the same
    40   * logical request.
    41   */
    42  public class Log4jServletFilter implements Filter {
    43
    44      private static final Logger LOGGER = StatusLogger.getLogger();
    45
    46      static final String ALREADY_FILTERED_ATTRIBUTE = Log4jServletFilter.class.getName() + ".FILTERED";
    47
    48      private ServletContext servletContext;
    49      private Log4jWebLifeCycle initializer;
    50
    51      @Override
    52      public void init(final FilterConfig filterConfig) throws ServletException {
    53          this.servletContext = filterConfig.getServletContext();
    54          LOGGER.debug("Log4jServletFilter initialized.");
    55
    56          this.initializer = WebLoggerContextUtils.getWebLifeCycle(this.servletContext);
    57          this.initializer.clearLoggerContext(); // the application is mostly finished starting up now
    58      }
    59
    60      @Override
    61      public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
    62              throws IOException, ServletException {
    63          if (request.getAttribute(ALREADY_FILTERED_ATTRIBUTE) != null) {
    64              chain.doFilter(request, response);
    65          } else {
    66              request.setAttribute(ALREADY_FILTERED_ATTRIBUTE, Boolean.TRUE);
    67
    68              try {
    69                  this.initializer.setLoggerContext();
    70
    71                  chain.doFilter(request, response);
    72              } finally {
    73                  this.initializer.clearLoggerContext();
    74              }
    75          }
    76      }
    77
    78      @Override
    79      public void destroy() {
    80          if (this.servletContext == null || this.initializer == null) {
    81              throw new IllegalStateException("Filter destroyed before it was initialized.");
    82          }
    83          LOGGER.debug("Log4jServletFilter destroyed.");
    84
    85          this.initializer.setLoggerContext(); // the application is just now starting to shut down
    86      }
    87  }