/*
    * 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 java.util.EnumSet;
  import java.util.Set;
  import javax.servlet.DispatcherType;
  import javax.servlet.FilterRegistration;
  import javax.servlet.ServletContainerInitializer;
  import javax.servlet.ServletContext;
  import javax.servlet.ServletException;
  
  import org.apache.logging.log4j.Logger;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   * In a Servlet 3.0 or newer environment, this initializer is responsible for starting up Log4j logging before anything
   * else happens in application initialization. For consistency across all containers, if the effective Servlet major
   * version of the application is less than 3.0, this initializer does nothing.
   */
  public class Log4jServletContainerInitializer implements ServletContainerInitializer {
  
      private static final Logger LOGGER = StatusLogger.getLogger();
  
      @Override
      public void onStartup(final Set<Class<?>> classes, final ServletContext servletContext) throws ServletException {
          if (servletContext.getMajorVersion() > 2 && servletContext.getEffectiveMajorVersion() > 2 &&
                  !"true".equalsIgnoreCase(servletContext.getInitParameter(
                          Log4jWebSupport.IS_LOG4J_AUTO_INITIALIZATION_DISABLED
                  ))) {
              LOGGER.debug("Log4jServletContainerInitializer starting up Log4j in Servlet 3.0+ environment.");
  
              final FilterRegistration.Dynamic filter =
                      servletContext.addFilter("log4jServletFilter", Log4jServletFilter.class);
              if (filter == null) {
                  LOGGER.warn("WARNING: In a Servlet 3.0+ application, you should not define a " +
                      "log4jServletFilter in web.xml. Log4j 2 normally does this for you automatically. Log4j 2 " +
                      "web auto-initialization has been canceled.");
                  return;
              }
  
              final Log4jWebLifeCycle initializer = WebLoggerContextUtils.getWebLifeCycle(servletContext);
              initializer.start();
              initializer.setLoggerContext(); // the application is just now starting to start up
  
              servletContext.addListener(new Log4jServletContextListener());
  
              filter.setAsyncSupported(true); // supporting async when the user isn't using async has no downsides
              filter.addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class), false, "/*");
          }
      }
  }