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 java.lang.reflect.Constructor;
020import java.util.Map;
021import java.util.Map.Entry;
022
023import org.apache.logging.log4j.core.ContextDataInjector;
024import org.apache.logging.log4j.core.LogEvent;
025import org.apache.logging.log4j.core.util.Loader;
026import org.apache.logging.log4j.util.IndexedStringMap;
027import org.apache.logging.log4j.util.PropertiesUtil;
028import org.apache.logging.log4j.util.ReadOnlyStringMap;
029import org.apache.logging.log4j.util.SortedArrayStringMap;
030import org.apache.logging.log4j.util.StringMap;
031
032/**
033 * Factory for creating the StringMap instances used to initialize LogEvents' {@linkplain LogEvent#getContextData()
034 * context data}. When context data is {@linkplain ContextDataInjector injected} into the log event, these StringMap
035 * instances may be either populated with key-value pairs from the context, or completely replaced altogether.
036 * <p>
037 * By default returns {@code SortedArrayStringMap} objects. Can be configured by setting system property
038 * {@code "log4j2.ContextData"} to the fully qualified class name of a class implementing the {@code StringMap}
039 * interface. The class must have a public default constructor, and if possible should also have a public constructor
040 * that takes a single {@code int} argument for the initial capacity.
041 * </p>
042 *
043 * @see LogEvent#getContextData()
044 * @see ContextDataInjector
045 * @see SortedArrayStringMap
046 * @since 2.7
047 */
048public class ContextDataFactory {
049    private static final String CLASS_NAME = PropertiesUtil.getProperties().getStringProperty("log4j2.ContextData");
050    private static final Class<? extends StringMap> CACHED_CLASS = createCachedClass(CLASS_NAME);
051
052    /**
053     * In LOG4J2-2649 (https://issues.apache.org/jira/browse/LOG4J2-2649),
054     * the reporter said some reason about using graalvm to static compile.
055     * In graalvm doc (https://github.com/oracle/graal/blob/master/substratevm/LIMITATIONS.md),
056     * graalvm is not support MethodHandle now, so the Constructor need not to return MethodHandle.
057     */
058    private static final Constructor<?> DEFAULT_CONSTRUCTOR = createDefaultConstructor(CACHED_CLASS);
059    private static final Constructor<?> INITIAL_CAPACITY_CONSTRUCTOR = createInitialCapacityConstructor(CACHED_CLASS);
060
061    private static final StringMap EMPTY_STRING_MAP = createContextData(0);
062
063    static {
064        EMPTY_STRING_MAP.freeze();
065    }
066
067    private static Class<? extends StringMap> createCachedClass(final String className) {
068        if (className == null) {
069            return null;
070        }
071        try {
072            return Loader.loadClass(className).asSubclass(IndexedStringMap.class);
073        } catch (final Exception any) {
074            return null;
075        }
076    }
077
078    private static Constructor<?> createDefaultConstructor(final Class<? extends StringMap> cachedClass){
079        if (cachedClass == null) {
080            return null;
081        }
082        try {
083            return cachedClass.getConstructor();
084        } catch (final NoSuchMethodException | IllegalAccessError ignored) {
085            return null;
086        }
087    }
088
089    private static Constructor<?> createInitialCapacityConstructor(final Class<? extends StringMap> cachedClass){
090        if (cachedClass == null) {
091            return null;
092        }
093        try {
094            return cachedClass.getConstructor(int.class);
095        } catch (final NoSuchMethodException | IllegalAccessError ignored) {
096            return null;
097        }
098    }
099
100    public static StringMap createContextData() {
101        if (DEFAULT_CONSTRUCTOR == null) {
102            return new SortedArrayStringMap();
103        }
104        try {
105            return (IndexedStringMap) DEFAULT_CONSTRUCTOR.newInstance();
106        } catch (final Throwable ignored) {
107            return new SortedArrayStringMap();
108        }
109    }
110
111    public static StringMap createContextData(final int initialCapacity) {
112        if (INITIAL_CAPACITY_CONSTRUCTOR == null) {
113            return new SortedArrayStringMap(initialCapacity);
114        }
115        try {
116            return (IndexedStringMap) INITIAL_CAPACITY_CONSTRUCTOR.newInstance(initialCapacity);
117        } catch (final Throwable ignored) {
118            return new SortedArrayStringMap(initialCapacity);
119        }
120    }
121
122    public static StringMap createContextData(final Map<String, String> context) {
123        final StringMap contextData = createContextData(context.size());
124        for (final Entry<String, String> entry : context.entrySet()) {
125            contextData.putValue(entry.getKey(), entry.getValue());
126        }
127        return contextData;
128    }
129
130    public static StringMap createContextData(final ReadOnlyStringMap readOnlyStringMap) {
131        final StringMap contextData = createContextData(readOnlyStringMap.size());
132        contextData.putAll(readOnlyStringMap);
133        return contextData;
134    }
135
136    /**
137     * An empty pre-frozen IndexedStringMap. The returned object may be shared.
138     *
139     * @return an empty pre-frozen IndexedStringMap
140     */
141    public static StringMap emptyFrozenContextData() {
142        return EMPTY_STRING_MAP;
143    }
144
145}