/*
    * 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.core.web;
  
  import javax.servlet.ServletContext;
  import javax.servlet.ServletContextEvent;
  import javax.servlet.ServletContextListener;
  
  import org.apache.logging.log4j.core.LoggerContext;
  import org.apache.logging.log4j.core.config.Configurator;
  import org.apache.logging.log4j.core.lookup.Interpolator;
  import org.apache.logging.log4j.core.lookup.StrLookup;
  import org.apache.logging.log4j.core.lookup.StrSubstitutor;
  
  /**
   * Saves the LoggerContext into the ServletContext as an attribute.
   */
  public class Log4jContextListener implements ServletContextListener {
  
      /**
       * The name of the attribute to use to store the LoggerContext into the ServletContext.
       */
      public static final String LOG4J_CONTEXT_ATTRIBUTE = "Log4jContext";
  
      /**
       * The location of the configuration.
       */
      public static final String LOG4J_CONFIG = "log4jConfiguration";
  
      /**
       * The name of the LoggerContext.
       */
      public static final String LOG4J_CONTEXT_NAME = "log4jContextName";
  
      private final StrSubstitutor subst = new StrSubstitutor(new Interpolator());
  
      /**
       * Initialize Logging for the web application.
       * @param event The ServletContextEvent.
       */
      @Override
      public void contextInitialized(final ServletContextEvent event) {
          final ServletContext context = event.getServletContext();
          final String locn = subst.replace(context.getInitParameter(LOG4J_CONFIG));
          String name = subst.replace(context.getInitParameter(LOG4J_CONTEXT_NAME));
          if (name == null) {
              name = context.getServletContextName();
          }
          if (name == null && locn == null) {
              context.log("No Log4j context configuration provided");
              return;
          }
          context.setAttribute(LOG4J_CONTEXT_ATTRIBUTE, Configurator.initialize(name, getClassLoader(context), locn));
      }
  
      /**
       * Shutdown logging for the web application.
       * @param event The ServletContextEvent.
       */
      @Override
      public void contextDestroyed(final ServletContextEvent event) {
          final LoggerContext ctx = (LoggerContext) event.getServletContext().getAttribute(LOG4J_CONTEXT_ATTRIBUTE);
          Configurator.shutdown(ctx);
      }
  
      private ClassLoader getClassLoader(final ServletContext context) {
          try {
              // if container is Servlet 3.0, use its getClassLoader method
              return (ClassLoader)context.getClass().getMethod("getClassLoader").invoke(context);
          } catch (Exception ignore) {
              // otherwise, use this class's class loader
              return Log4jContextListener.class.getClassLoader();
          }
      }
  }