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 }