    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.web;
    018
    019    import java.util.concurrent.locks.Lock;
    020    import java.util.concurrent.locks.ReentrantLock;
    021    import javax.servlet.ServletContext;
    022
    023    import org.apache.logging.log4j.LogManager;
    024    import org.apache.logging.log4j.core.LoggerContext;
    025    import org.apache.logging.log4j.core.impl.ContextAnchor;
    026
    027    /**
    028     * Convenience methods for retrieving the {@link org.apache.logging.log4j.core.LoggerContext} associated with a
    029     * particular ServletContext. These methods are most particularly useful for asynchronous servlets where the
    030     * Thread Context ClassLoader (TCCL) is potentially different from the TCCL used by the
    031     * Servlet container that bootstrapped Log4j.
    032     *
    033     * @since 2.0.1
    034     */
    035    public final class WebLoggerContextUtils {
    036        private WebLoggerContextUtils() {
    037        }
    038
    039        private static final Lock WEB_SUPPORT_LOOKUP = new ReentrantLock();
    040
    041        /**
    042         * Finds the main {@link org.apache.logging.log4j.core.LoggerContext} configured for the given ServletContext.
    043         *
    044         * @param servletContext the ServletContext to locate a LoggerContext for
    045         * @return the LoggerContext for the given ServletContext
    046         * @since 2.0.1
    047         */
    048        public static LoggerContext getWebLoggerContext(final ServletContext servletContext) {
    049            return (LoggerContext) servletContext.getAttribute(Log4jWebSupport.CONTEXT_ATTRIBUTE);
    050        }
    051
    052        /**
    053         * Finds the main {@link org.apache.logging.log4j.core.LoggerContext} configured for the given ServletContext.
    054         *
    055         * @param servletContext the ServletContext to locate a LoggerContext for
    056         * @return the LoggerContext for the given ServletContext or {@code null} if none was set
    057         * @throws java.lang.IllegalStateException if no LoggerContext could be found on the given ServletContext
    058         * @since 2.0.1
    059         */
    060        public static LoggerContext getRequiredWebLoggerContext(final ServletContext servletContext) {
    061            final LoggerContext loggerContext = getWebLoggerContext(servletContext);
    062            if (loggerContext == null) {
    063                throw new IllegalStateException(
    064                    "No LoggerContext found in ServletContext attribute " + Log4jWebSupport.CONTEXT_ATTRIBUTE);
    065            }
    066            return loggerContext;
    067        }
    068
    069        /**
    070         * Finds or initializes the {@link org.apache.logging.log4j.web.Log4jWebLifeCycle} singleton for the given
    071         * ServletContext.
    072         *
    073         * @param servletContext the ServletContext to get the Log4jWebLifeCycle for
    074         * @return the Log4jWebLifeCycle for the given ServletContext
    075         * @since 2.0.1
    076         */
    077        public static Log4jWebLifeCycle getWebLifeCycle(final ServletContext servletContext) {
    078            WEB_SUPPORT_LOOKUP.lock();
    079            try {
    080                Log4jWebLifeCycle webLifeCycle = (Log4jWebLifeCycle) servletContext.getAttribute(
    081                    Log4jWebSupport.SUPPORT_ATTRIBUTE);
    082                if (webLifeCycle == null) {
    083                    webLifeCycle = Log4jWebInitializerImpl.initialize(servletContext);
    084                }
    085                return webLifeCycle;
    086            } finally {
    087                WEB_SUPPORT_LOOKUP.unlock();
    088            }
    089        }
    090
    091        /**
    092         * Wraps a Runnable instance by setting its thread context {@link org.apache.logging.log4j.core.LoggerContext}
    093         * before execution and clearing it after execution.
    094         *
    095         * @param servletContext the ServletContext to locate a LoggerContext for
    096         * @param runnable       the Runnable to wrap execution for
    097         * @return a wrapped Runnable
    098         * @since 2.0.1
    099         */
    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    }