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/MainMapLookup.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.Map;

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

/**
 * A map-based lookup for main arguments.
 *
 * See {@link #setMainArguments(String[])}.
 *
 * @since 2.4
 */
@Plugin(name = "main", category = StrLookup.CATEGORY)
public class MainMapLookup extends MapLookup {

    /**
     * A singleton used by a main method to save its arguments.
     */
    static final MapLookup MAIN_SINGLETON = new MapLookup(MapLookup.newMap(0));

    /**
     * Constructor when used directly as a plugin.
     */
    public MainMapLookup() {
        // no-init
    }

    public MainMapLookup(final Map<String, String> map) {
        super(map);
    }

    /**
     * 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>
     *<p>Note: Many applications use leading dashes to identify command arguments. Specifying {@code "main:--file}
     * would result in the lookup failing because it would look for a variable named "main" with a default
     * value of "-file". To avoid this the ":" separating the Lookup name from the key must be followed by
     * a backslash as an escape character.</p>
     *
     * @param args
     *        An application's {@code public static main(String[])} arguments.
     */
    public static void setMainArguments(final String... args) {
        if (args == null) {
            return;
        }
        initMap(args, MainMapLookup.MAIN_SINGLETON.getMap());
    }

    @Override
    public String lookup(final LogEvent event, final String key) {
        return MAIN_SINGLETON.getMap().get(key);
    }

    @Override
    public String lookup(final String key) {
        return MAIN_SINGLETON.getMap().get(key);
    }

}

⏎ org/apache/logging/log4j/core/lookup/MainMapLookup.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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