    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements. See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache license, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License. You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the license for the specific language governing permissions and
    015     * limitations under the license.
    016     */
    017    package org.apache.logging.log4j.spi;
    018
    019    import java.util.Map;
    020    import java.util.WeakHashMap;
    021    import java.util.concurrent.ConcurrentHashMap;
    022    import java.util.concurrent.ConcurrentMap;
    023
    024    import org.apache.logging.log4j.LogManager;
    025    import org.apache.logging.log4j.util.LoaderUtil;
    026
    027    /**
    028     * Provides an abstract base class to use for implementing LoggerAdapter.
    029     * @param <L> the Logger class to adapt
    030     * @since 2.1
    031     */
    032    public abstract class AbstractLoggerAdapter<L> implements LoggerAdapter<L> {
    033
    034        /**
    035         * A map to store loggers for their given LoggerContexts.
    036         */
    037        protected final Map<LoggerContext, ConcurrentMap<String, L>> registry =
    038            new WeakHashMap<LoggerContext, ConcurrentMap<String, L>>();
    039
    040        @Override
    041        public L getLogger(final String name) {
    042            final LoggerContext context = getContext();
    043            final ConcurrentMap<String, L> loggers = getLoggersInContext(context);
    044            if (loggers.containsKey(name)) {
    045                return loggers.get(name);
    046            }
    047            loggers.putIfAbsent(name, newLogger(name, context));
    048            return loggers.get(name);
    049        }
    050
    051        /**
    052         * Gets or creates the ConcurrentMap of named loggers for a given LoggerContext.
    053         *
    054         * @param context the LoggerContext to get loggers for
    055         * @return the map of loggers for the given LoggerContext
    056         */
    057        public ConcurrentMap<String, L> getLoggersInContext(final LoggerContext context) {
    058            synchronized (registry) {
    059                ConcurrentMap<String, L> loggers = registry.get(context);
    060                if (loggers == null) {
    061                    loggers = new ConcurrentHashMap<String, L>();
    062                    registry.put(context, loggers);
    063                }
    064                return loggers;
    065            }
    066        }
    067
    068        /**
    069         * Creates a new named logger for a given {@link LoggerContext}.
    070         *
    071         * @param name    the name of the logger to create
    072         * @param context the LoggerContext this logger will be associated with
    073         * @return the new named logger
    074         */
    075        protected abstract L newLogger(final String name, final LoggerContext context);
    076
    077        /**
    078         * Gets the {@link LoggerContext} that should be used to look up or create loggers. This is similar in spirit to
    079         * the {@code ContextSelector} class in {@code log4j-core}. However, implementations can rely on their own
    080         * framework's separation of contexts instead (or simply use a singleton).
    081         *
    082         * @return the LoggerContext to be used for lookup and creation purposes
    083         * @see org.apache.logging.log4j.LogManager#getContext(ClassLoader, boolean)
    084         * @see org.apache.logging.log4j.LogManager#getContext(String, boolean)
    085         */
    086        protected abstract LoggerContext getContext();
    087
    088        /**
    089         * Gets the {@link LoggerContext} associated with the given caller class.
    090         *
    091         * @param callerClass the caller class
    092         * @return the LoggerContext for the calling class
    093         */
    094        protected LoggerContext getContext(final Class<?> callerClass) {
    095            ClassLoader cl = null;
    096            if (callerClass != null) {
    097                cl = callerClass.getClassLoader();
    098            }
    099            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    }