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.core.impl; 18 19 import org.apache.logging.log4j.ThreadContext; 20 import org.apache.logging.log4j.core.ContextDataInjector; 21 import org.apache.logging.log4j.core.LogEvent; 22 import org.apache.logging.log4j.core.util.Loader; 23 import org.apache.logging.log4j.spi.CopyOnWrite; 24 import org.apache.logging.log4j.spi.DefaultThreadContextMap; 25 import org.apache.logging.log4j.spi.ReadOnlyThreadContextMap; 26 import org.apache.logging.log4j.status.StatusLogger; 27 import org.apache.logging.log4j.util.PropertiesUtil; 28 import org.apache.logging.log4j.util.ReadOnlyStringMap; 29 30 /** 31 * Factory for ContextDataInjectors. Returns a new {@code ContextDataInjector} instance based on the value of system 32 * property {@code log4j2.ContextDataInjector}. Users may use this system property to specify the fully qualified class 33 * name of a class that implements the {@code ContextDataInjector} interface. 34 * If no value was specified this factory method returns one of the injectors defined in 35 * {@code ThreadContextDataInjector}. 36 * 37 * @see ContextDataInjector 38 * @see ReadOnlyStringMap 39 * @see ThreadContextDataInjector 40 * @see LogEvent#getContextData() 41 * @since 2.7 42 */ 43 public class ContextDataInjectorFactory { 44 45 /** 46 * Returns a new {@code ContextDataInjector} instance based on the value of system property 47 * {@code log4j2.ContextDataInjector}. If no value was specified this factory method returns one of the 48 * {@code ContextDataInjector} classes defined in {@link ThreadContextDataInjector} which is most appropriate for 49 * the ThreadContext implementation. 50 * <p> 51 * Users may use this system property to specify the fully qualified class name of a class that implements the 52 * {@code ContextDataInjector} interface. 53 * </p><p> 54 * When providing a custom {@code ContextDataInjector}, be aware that this method may be invoked multiple times by 55 * the various components in Log4j that need access to context data. 56 * This includes the object(s) that populate log events, but also various lookups and filters that look at 57 * context data to determine whether an event should be logged. 58 * </p> 59 * 60 * @return a ContextDataInjector that populates the {@code ReadOnlyStringMap} of all {@code LogEvent} objects 61 * @see LogEvent#getContextData() 62 * @see ContextDataInjector 63 */ 64 public static ContextDataInjector createInjector() { 65 final String className = PropertiesUtil.getProperties().getStringProperty("log4j2.ContextDataInjector"); 66 if (className == null) { 67 return createDefaultInjector(); 68 } 69 try { 70 final Class<? extends ContextDataInjector> cls = Loader.loadClass(className).asSubclass( 71 ContextDataInjector.class); 72 return cls.newInstance(); 73 } catch (final Exception dynamicFailed) { 74 final ContextDataInjector result = createDefaultInjector(); 75 StatusLogger.getLogger().warn( 76 "Could not create ContextDataInjector for '{}', using default {}: {}", 77 className, result.getClass().getName(), dynamicFailed); 78 return result; 79 } 80 } 81 82 private static ContextDataInjector createDefaultInjector() { 83 final ReadOnlyThreadContextMap threadContextMap = ThreadContext.getThreadContextMap(); 84 85 // note: map may be null (if legacy custom ThreadContextMap was installed by user) 86 if (threadContextMap instanceof DefaultThreadContextMap || threadContextMap == null) { 87 return new ThreadContextDataInjector.ForDefaultThreadContextMap(); // for non StringMap-based context maps 88 } 89 if (threadContextMap instanceof CopyOnWrite) { 90 return new ThreadContextDataInjector.ForCopyOnWriteThreadContextMap(); 91 } 92 return new ThreadContextDataInjector.ForGarbageFreeThreadContextMap(); 93 } 94 }