Apache Log4j Core Implementation provides the functional components of the logging system. Users are free to create their own plugins and include them in the logging configuration. Apache Log4j Core is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j Core Implementation is provided in a separate JAR file like log4j-core-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like apache-log4j-2.14.1-bin.zip and source package like apache-log4j-2.14.1-src.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Core Implementation 2.14.1 below.

⏎ org/apache/logging/log4j/core/lookup/MapLookup.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache license, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the license for the specific language governing permissions and
 * limitations under the license.
 */
package org.apache.logging.log4j.core.lookup;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.message.MapMessage;

/**
 * A map-based lookup.
 */
@Plugin(name = "map", category = StrLookup.CATEGORY)
public class MapLookup implements StrLookup {

    /**
     * Map keys are variable names and value.
     */
    private final Map<String, String> map;

    /**
     * Constructor when used directly as a plugin.
     */
    public MapLookup() {
        this.map = null;
    }

    /**
     * Creates a new instance backed by a Map. Used by the default lookup.
     *
     * @param map
     *        the map of keys to values, may be null
     */
    public MapLookup(final Map<String, String> map) {
        this.map = map;
    }

    static Map<String, String> initMap(final String[] srcArgs, final Map<String, String> destMap) {
        for (int i = 0; i < srcArgs.length; i++) {
            final int next = i + 1;
            final String value = srcArgs[i];
            destMap.put(Integer.toString(i), value);
            destMap.put(value, next < srcArgs.length ? srcArgs[next] : null);
        }
        return destMap;
    }

    static HashMap<String, String> newMap(final int initialCapacity) {
        return new HashMap<>(initialCapacity);
    }

    /**
     * An application's {@code public static main(String[])} method calls this method to make its main arguments
     * available for lookup with the prefix {@code main}.
     * <p>
     * The map provides two kinds of access: First by index, starting at {@code "0"}, {@code "1"} and so on. For
     * example, the command line {@code --file path/file.txt -x 2} can be accessed from a configuration file with:
     * </p>
     * <ul>
     * <li>{@code "main:0"} = {@code "--file"}</li>
     * <li>{@code "main:1"} = {@code "path/file.txt"}</li>
     * <li>{@code "main:2"} = {@code "-x"}</li>
     * <li>{@code "main:3"} = {@code "2"}</li>
     * </ul>
     * <p>
     * Second using the argument at position n as the key to access the value at n+1.
     * </p>
     * <ul>
     * <li>{@code "main:--file"} = {@code "path/file.txt"}</li>
     * <li>{@code "main:-x"} = {@code "2"}</li>
     * </ul>
     *
     * @param args
     *        An application's {@code public static main(String[])} arguments.
     * @since 2.1
     * @deprecated As of 2.4, use {@link MainMapLookup#setMainArguments(String[])}
     */
    @Deprecated
    public static void setMainArguments(final String... args) {
        MainMapLookup.setMainArguments(args);
    }

    static Map<String, String> toMap(final List<String> args) {
        if (args == null) {
            return null;
        }
        final int size = args.size();
        return initMap(args.toArray(new String[size]), newMap(size));
    }

    static Map<String, String> toMap(final String[] args) {
        if (args == null) {
            return null;
        }
        return initMap(args, newMap(args.length));
    }

    protected Map<String, String> getMap() {
        return map;
    }

    @Override
    public String lookup(final LogEvent event, final String key) {
        final boolean isMapMessage = event != null && event.getMessage() instanceof MapMessage;
        if (map == null && !isMapMessage) {
            return null;
        }
        if (map != null && map.containsKey(key)) {
            final String obj = map.get(key);
            if (obj != null) {
                return obj;
            }
        }
        if (isMapMessage) {
            return ((MapMessage) event.getMessage()).get(key);
        }
        return null;
    }

    /**
     * Looks up a String key to a String value using the map.
     * <p>
     * If the map is null, then null is returned. The map result object is converted to a string using toString().
     * </p>
     *
     * @param key
     *        the key to be looked up, may be null
     * @return the matching value, null if no match
     */
    @Override
    public String lookup(final String key) {
        if (map == null) {
            return null;
        }
        return map.get(key);
    }

}

⏎ org/apache/logging/log4j/core/lookup/MapLookup.java

Or download all of them as a single archive file:

File name: log4j-core-2.14.1-sources.jar
File size: 1281358 bytes
Release date: 2021-03-06
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