/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements. See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache license, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License. You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the license for the specific language governing permissions and
   * limitations under the license.
   */
  package org.apache.logging.log4j.web;
  
  import javax.servlet.ServletContext;
  import javax.servlet.ServletContextEvent;
  import javax.servlet.ServletContextListener;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * In environments older than Servlet 3.0, this initializer is responsible for starting up Log4j logging before anything
   * else happens in application initialization. In all environments, this shuts down Log4j after the application shuts
   * down.
   */
  public class Log4jServletContextListener implements ServletContextListener {
  
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      private ServletContext servletContext;
      private Log4jWebLifeCycle initializer;
  
      @Override
      public void contextInitialized(final ServletContextEvent event) {
          this.servletContext = event.getServletContext();
          LOGGER.debug("Log4jServletContextListener ensuring that Log4j starts up properly.");
  
          this.initializer = WebLoggerContextUtils.getWebLifeCycle(this.servletContext);
          try {
              this.initializer.start();
              this.initializer.setLoggerContext(); // the application is just now starting to start up
          } catch (final IllegalStateException e) {
              throw new IllegalStateException("Failed to initialize Log4j properly.", e);
          }
      }
  
      @Override
      public void contextDestroyed(final ServletContextEvent event) {
          if (this.servletContext == null || this.initializer == null) {
              throw new IllegalStateException("Context destroyed before it was initialized.");
          }
          LOGGER.debug("Log4jServletContextListener ensuring that Log4j shuts down properly.");
  
          this.initializer.clearLoggerContext(); // the application is finished shutting down now
          this.initializer.stop();
      }
  }