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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.util.concurrent.locks.Lock;
    20  import java.util.concurrent.locks.ReentrantLock;
    21  import javax.servlet.ServletContext;
    22
    23  import org.apache.logging.log4j.LogManager;
    24  import org.apache.logging.log4j.core.LoggerContext;
    25  import org.apache.logging.log4j.core.impl.ContextAnchor;
    26
    27  /**
    28   * Convenience methods for retrieving the {@link org.apache.logging.log4j.core.LoggerContext} associated with a
    29   * particular ServletContext. These methods are most particularly useful for asynchronous servlets where the
    30   * Thread Context ClassLoader (TCCL) is potentially different from the TCCL used by the
    31   * Servlet container that bootstrapped Log4j.
    32   *
    33   * @since 2.0.1
    34   */
    35  public final class WebLoggerContextUtils {
    36      private WebLoggerContextUtils() {
    37      }
    38
    39      private static final Lock WEB_SUPPORT_LOOKUP = new ReentrantLock();
    40
    41      /**
    42       * Finds the main {@link org.apache.logging.log4j.core.LoggerContext} configured for the given ServletContext.
    43       *
    44       * @param servletContext the ServletContext to locate a LoggerContext for
    45       * @return the LoggerContext for the given ServletContext
    46       * @since 2.0.1
    47       */
    48      public static LoggerContext getWebLoggerContext(final ServletContext servletContext) {
    49          return (LoggerContext) servletContext.getAttribute(Log4jWebSupport.CONTEXT_ATTRIBUTE);
    50      }
    51
    52      /**
    53       * Finds the main {@link org.apache.logging.log4j.core.LoggerContext} configured for the given ServletContext.
    54       *
    55       * @param servletContext the ServletContext to locate a LoggerContext for
    56       * @return the LoggerContext for the given ServletContext or {@code null} if none was set
    57       * @throws java.lang.IllegalStateException if no LoggerContext could be found on the given ServletContext
    58       * @since 2.0.1
    59       */
    60      public static LoggerContext getRequiredWebLoggerContext(final ServletContext servletContext) {
    61          final LoggerContext loggerContext = getWebLoggerContext(servletContext);
    62          if (loggerContext == null) {
    63              throw new IllegalStateException(
    64                  "No LoggerContext found in ServletContext attribute " + Log4jWebSupport.CONTEXT_ATTRIBUTE);
    65          }
    66          return loggerContext;
    67      }
    68
    69      /**
    70       * Finds or initializes the {@link org.apache.logging.log4j.web.Log4jWebLifeCycle} singleton for the given
    71       * ServletContext.
    72       *
    73       * @param servletContext the ServletContext to get the Log4jWebLifeCycle for
    74       * @return the Log4jWebLifeCycle for the given ServletContext
    75       * @since 2.0.1
    76       */
    77      public static Log4jWebLifeCycle getWebLifeCycle(final ServletContext servletContext) {
    78          WEB_SUPPORT_LOOKUP.lock();
    79          try {
    80              Log4jWebLifeCycle webLifeCycle = (Log4jWebLifeCycle) servletContext.getAttribute(
    81                  Log4jWebSupport.SUPPORT_ATTRIBUTE);
    82              if (webLifeCycle == null) {
    83                  webLifeCycle = Log4jWebInitializerImpl.initialize(servletContext);
    84              }
    85              return webLifeCycle;
    86          } finally {
    87              WEB_SUPPORT_LOOKUP.unlock();
    88          }
    89      }
    90
    91      /**
    92       * Wraps a Runnable instance by setting its thread context {@link org.apache.logging.log4j.core.LoggerContext}
    93       * before execution and clearing it after execution.
    94       *
    95       * @param servletContext the ServletContext to locate a LoggerContext for
    96       * @param runnable       the Runnable to wrap execution for
    97       * @return a wrapped Runnable
    98       * @since 2.0.1
    99       */
    100     public static Runnable wrapExecutionContext(final ServletContext servletContext, final Runnable runnable) {
    101         return new Runnable() {
    102             @Override
    103             public void run() {
    104                 final Log4jWebSupport webSupport = getWebLifeCycle(servletContext);
    105                 webSupport.setLoggerContext();
    106                 try {
    107                     runnable.run();
    108                 } finally {
    109                     webSupport.clearLoggerContext();
    110                 }
    111             }
    112         };
    113     }
    114
    115     /**
    116      * Gets the current {@link ServletContext} if it has already been assigned to a LoggerContext's external context.
    117      *
    118      * @return the current ServletContext attached to a LoggerContext or {@code null} if none could be found
    119      * @since 2.1
    120      */
    121     public static ServletContext getServletContext() {
    122         org.apache.logging.log4j.spi.LoggerContext lc = ContextAnchor.THREAD_CONTEXT.get();
    123         if (lc == null) {
    124             lc = LogManager.getContext(false);
    125         }
    126         return lc == null ? null :
    127             lc.getExternalContext() instanceof ServletContext ? (ServletContext) lc.getExternalContext() : null;
    128     }
    129 }