Apache Log4j to SLF4J Adapter allows applications coded to the Log4j 2 API to be routed to SLF4J. Use of this adapter may cause some loss of performance as the Log4j 2 Messages must be formatted before they can be passed to SLF4J.

Bytecode (Java 8) for Apache Log4j to SLF4J Adapter is provided in a separate JAR file like log4j-to-slf4j-2.14.1.jar.

Source Code files for Apache Log4j IOStreams 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 to SLF4J Adapter 2.14.1 below.

⏎ org/apache/logging/slf4j/MDCContextMap.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.slf4j;

import java.util.Map;
import java.util.Map.Entry;

import org.apache.logging.log4j.spi.CleanableThreadContextMap;
import org.apache.logging.log4j.util.SortedArrayStringMap;
import org.apache.logging.log4j.util.StringMap;
import org.slf4j.MDC;

/**
 * Bind the ThreadContextMap to the SLF4J MDC.
 */
public class MDCContextMap implements CleanableThreadContextMap {

    private static final StringMap EMPTY_CONTEXT_DATA = new SortedArrayStringMap(1);
    static {
        EMPTY_CONTEXT_DATA.freeze();
    }

    @Override
    public void put(final String key, final String value) {
        MDC.put(key, value);
    }

    @Override
    public void putAll(final Map<String, String> m) {
        for (final Entry<String, String> entry : m.entrySet()) {
            MDC.put(entry.getKey(), entry.getValue());
        }
    }

    @Override
    public String get(final String key) {
        return MDC.get(key);
    }

    @Override
    public void remove(final String key) {
        MDC.remove(key);
    }


    @Override
    public void removeAll(final Iterable<String> keys) {
        for (final String key : keys) {
            MDC.remove(key);
        }
    }

    @Override
    public void clear() {
        MDC.clear();
    }

    @Override
    public boolean containsKey(final String key) {
        Map<String, String> map = MDC.getCopyOfContextMap();
        return map != null && map.containsKey(key);
    }

    @Override
    @SuppressWarnings("unchecked") // nothing we can do about this, restricted by SLF4J API
    public Map<String, String> getCopy() {
        return MDC.getCopyOfContextMap();
    }

    @Override
    @SuppressWarnings("unchecked") // nothing we can do about this, restricted by SLF4J API
    public Map<String, String> getImmutableMapOrNull() {
        return MDC.getCopyOfContextMap();
    }

    @Override
    public boolean isEmpty() {
        Map<String, String> map = MDC.getCopyOfContextMap();
        return map == null || map.isEmpty();
    }

    @Override
    public StringMap getReadOnlyContextData() {
        final Map<String, String> copy = getCopy();
        if (copy.isEmpty()) {
            return EMPTY_CONTEXT_DATA;
        }
        final StringMap result = new SortedArrayStringMap();
        for (final Entry<String, String> entry : copy.entrySet()) {
            result.putValue(entry.getKey(), entry.getValue());
        }
        return result;
    }
}

⏎ org/apache/logging/slf4j/MDCContextMap.java

Or download all of them as a single archive file:

File name: log4j-to-slf4j-2.14.1-sources.jar
File size: 15755 bytes
Release date: 2021-03-06
Download 

⇒ Source Code for Apache Log4j IOStreams

⇐ Source Code for Apache Log4j SLF4J Binding

⇑ Downloading and Reviewing Apache Log4j Packages

⇑⇑ FAQ for Apache Log4j