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 */ 017package org.apache.logging.log4j.core.impl; 018 019import org.apache.logging.log4j.ThreadContext; 020import org.apache.logging.log4j.core.ContextDataInjector; 021import org.apache.logging.log4j.core.LogEvent; 022import org.apache.logging.log4j.core.util.Loader; 023import org.apache.logging.log4j.spi.CopyOnWrite; 024import org.apache.logging.log4j.spi.DefaultThreadContextMap; 025import org.apache.logging.log4j.spi.ReadOnlyThreadContextMap; 026import org.apache.logging.log4j.status.StatusLogger; 027import org.apache.logging.log4j.util.PropertiesUtil; 028import org.apache.logging.log4j.util.ReadOnlyStringMap; 029 030/** 031 * Factory for ContextDataInjectors. Returns a new {@code ContextDataInjector} instance based on the value of system 032 * property {@code log4j2.ContextDataInjector}. Users may use this system property to specify the fully qualified class 033 * name of a class that implements the {@code ContextDataInjector} interface. 034 * If no value was specified this factory method returns one of the injectors defined in 035 * {@code ThreadContextDataInjector}. 036 * 037 * @see ContextDataInjector 038 * @see ReadOnlyStringMap 039 * @see ThreadContextDataInjector 040 * @see LogEvent#getContextData() 041 * @since 2.7 042 */ 043public class ContextDataInjectorFactory { 044 045 /** 046 * Returns a new {@code ContextDataInjector} instance based on the value of system property 047 * {@code log4j2.ContextDataInjector}. If no value was specified this factory method returns one of the 048 * {@code ContextDataInjector} classes defined in {@link ThreadContextDataInjector} which is most appropriate for 049 * the ThreadContext implementation. 050 * <p> 051 * Users may use this system property to specify the fully qualified class name of a class that implements the 052 * {@code ContextDataInjector} interface. 053 * </p><p> 054 * When providing a custom {@code ContextDataInjector}, be aware that this method may be invoked multiple times by 055 * the various components in Log4j that need access to context data. 056 * This includes the object(s) that populate log events, but also various lookups and filters that look at 057 * context data to determine whether an event should be logged. 058 * </p> 059 * 060 * @return a ContextDataInjector that populates the {@code ReadOnlyStringMap} of all {@code LogEvent} objects 061 * @see LogEvent#getContextData() 062 * @see ContextDataInjector 063 */ 064 public static ContextDataInjector createInjector() { 065 final String className = PropertiesUtil.getProperties().getStringProperty("log4j2.ContextDataInjector"); 066 if (className == null) { 067 return createDefaultInjector(); 068 } 069 try { 070 final Class<? extends ContextDataInjector> cls = Loader.loadClass(className).asSubclass( 071 ContextDataInjector.class); 072 return cls.newInstance(); 073 } catch (final Exception dynamicFailed) { 074 final ContextDataInjector result = createDefaultInjector(); 075 StatusLogger.getLogger().warn( 076 "Could not create ContextDataInjector for '{}', using default {}: {}", 077 className, result.getClass().getName(), dynamicFailed); 078 return result; 079 } 080 } 081 082 private static ContextDataInjector createDefaultInjector() { 083 final ReadOnlyThreadContextMap threadContextMap = ThreadContext.getThreadContextMap(); 084 085 // note: map may be null (if legacy custom ThreadContextMap was installed by user) 086 if (threadContextMap instanceof DefaultThreadContextMap || threadContextMap == null) { 087 return new ThreadContextDataInjector.ForDefaultThreadContextMap(); // for non StringMap-based context maps 088 } 089 if (threadContextMap instanceof CopyOnWrite) { 090 return new ThreadContextDataInjector.ForCopyOnWriteThreadContextMap(); 091 } 092 return new ThreadContextDataInjector.ForGarbageFreeThreadContextMap(); 093 } 094}