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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.spi;
    18
    19  import java.util.Map;
    20  import java.util.WeakHashMap;
    21  import java.util.concurrent.ConcurrentHashMap;
    22  import java.util.concurrent.ConcurrentMap;
    23
    24  import org.apache.logging.log4j.LogManager;
    25  import org.apache.logging.log4j.util.LoaderUtil;
    26
    27  /**
    28   * Provides an abstract base class to use for implementing LoggerAdapter.
    29   * @param <L> the Logger class to adapt
    30   * @since 2.1
    31   */
    32  public abstract class AbstractLoggerAdapter<L> implements LoggerAdapter<L> {
    33
    34      /**
    35       * A map to store loggers for their given LoggerContexts.
    36       */
    37      protected final Map<LoggerContext, ConcurrentMap<String, L>> registry =
    38          new WeakHashMap<LoggerContext, ConcurrentMap<String, L>>();
    39
    40      @Override
    41      public L getLogger(final String name) {
    42          final LoggerContext context = getContext();
    43          final ConcurrentMap<String, L> loggers = getLoggersInContext(context);
    44          if (loggers.containsKey(name)) {
    45              return loggers.get(name);
    46          }
    47          loggers.putIfAbsent(name, newLogger(name, context));
    48          return loggers.get(name);
    49      }
    50
    51      /**
    52       * Gets or creates the ConcurrentMap of named loggers for a given LoggerContext.
    53       *
    54       * @param context the LoggerContext to get loggers for
    55       * @return the map of loggers for the given LoggerContext
    56       */
    57      public ConcurrentMap<String, L> getLoggersInContext(final LoggerContext context) {
    58          synchronized (registry) {
    59              ConcurrentMap<String, L> loggers = registry.get(context);
    60              if (loggers == null) {
    61                  loggers = new ConcurrentHashMap<String, L>();
    62                  registry.put(context, loggers);
    63              }
    64              return loggers;
    65          }
    66      }
    67
    68      /**
    69       * Creates a new named logger for a given {@link LoggerContext}.
    70       *
    71       * @param name    the name of the logger to create
    72       * @param context the LoggerContext this logger will be associated with
    73       * @return the new named logger
    74       */
    75      protected abstract L newLogger(final String name, final LoggerContext context);
    76
    77      /**
    78       * Gets the {@link LoggerContext} that should be used to look up or create loggers. This is similar in spirit to
    79       * the {@code ContextSelector} class in {@code log4j-core}. However, implementations can rely on their own
    80       * framework's separation of contexts instead (or simply use a singleton).
    81       *
    82       * @return the LoggerContext to be used for lookup and creation purposes
    83       * @see org.apache.logging.log4j.LogManager#getContext(ClassLoader, boolean)
    84       * @see org.apache.logging.log4j.LogManager#getContext(String, boolean)
    85       */
    86      protected abstract LoggerContext getContext();
    87
    88      /**
    89       * Gets the {@link LoggerContext} associated with the given caller class.
    90       *
    91       * @param callerClass the caller class
    92       * @return the LoggerContext for the calling class
    93       */
    94      protected LoggerContext getContext(final Class<?> callerClass) {
    95          ClassLoader cl = null;
    96          if (callerClass != null) {
    97              cl = callerClass.getClassLoader();
    98          }
    99          if (cl == null) {
    100             cl = LoaderUtil.getThreadContextClassLoader();
    101         }
    102         return LogManager.getContext(cl, false);
    103     }
    104
    105     @Override
    106     public void close() {
    107         registry.clear();
    108     }
    109 }