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    }