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 * <b>Note:</b> It is no longer recommended that users provide a custom implementation of the ContextDataInjector.
52 * Instead, provide a {@code ContextDataProvider}.
53 * </p>
54 * <p>
55 * Users may use this system property to specify the fully qualified class name of a class that implements the
56 * {@code ContextDataInjector} interface.
57 * </p><p>
58 * When providing a custom {@code ContextDataInjector}, be aware that this method may be invoked multiple times by
59 * the various components in Log4j that need access to context data.
60 * This includes the object(s) that populate log events, but also various lookups and filters that look at
61 * context data to determine whether an event should be logged.
62 * </p>
63 *
64 * @return a ContextDataInjector that populates the {@code ReadOnlyStringMap} of all {@code LogEvent} objects
65 * @see LogEvent#getContextData()
66 * @see ContextDataInjector
67 */
68 public static ContextDataInjector createInjector() {
69 final String className = PropertiesUtil.getProperties().getStringProperty("log4j2.ContextDataInjector");
70 if (className == null) {
71 return createDefaultInjector();
72 }
73 try {
74 final Class<? extends ContextDataInjector> cls = Loader.loadClass(className).asSubclass(
75 ContextDataInjector.class);
76 return cls.newInstance();
77 } catch (final Exception dynamicFailed) {
78 final ContextDataInjector result = createDefaultInjector();
79 StatusLogger.getLogger().warn(
80 "Could not create ContextDataInjector for '{}', using default {}: {}",
81 className, result.getClass().getName(), dynamicFailed);
82 return result;
83 }
84 }
85
86 private static ContextDataInjector createDefaultInjector() {
87 final ReadOnlyThreadContextMap threadContextMap = ThreadContext.getThreadContextMap();
88
89 // note: map may be null (if legacy custom ThreadContextMap was installed by user)
90 if (threadContextMap instanceof DefaultThreadContextMap || threadContextMap == null) {
91 return new ThreadContextDataInjector.ForDefaultThreadContextMap(); // for non StringMap-based context maps
92 }
93 if (threadContextMap instanceof CopyOnWrite) {
94 return new ThreadContextDataInjector.ForCopyOnWriteThreadContextMap();
95 }
96 return new ThreadContextDataInjector.ForGarbageFreeThreadContextMap();
97 }
98 }