Apache Log4j API provides the interface that applications should code to and provides the adapter components required for implementers to create a logging implementation. Apache Log4j API is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j API is provided in a separate JAR file like log4j-api-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 API 2.14.1 below.

⏎ org/apache/logging/log4j/util/MessageSupplier.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.util;

import org.apache.logging.log4j.message.Message;

/**
 * Classes implementing this interface know how to supply {@link Message}s.
 *
 * <p>This is a <a href="https://docs.oracle.com/javase/8/docs/api/java/util/function/package-summary.html">functional
 * interface</a> intended to support lambda expressions in log4j 2.
 *
 * <p>Implementors are free to cache values or return a new or distinct value each time the supplier is invoked.
 *
 * <p><strong>DEPRECATED:</strong> this class should not normally be used outside a Java 8+ lambda syntax. Instead,
 * {@link Supplier Supplier<Message>} should be used as an anonymous class. Both this and {@link Supplier} will be
 * removed in 3.0.
 * </p>
 *
 * @since 2.4
 */
public interface MessageSupplier {

    /**
     * Gets a Message.
     *
     * @return a Message
     */
    Message get();
}

⏎ org/apache/logging/log4j/util/MessageSupplier.java

Or download all of them as a single archive file:

File name: log4j-api-2.14.1-sources.jar
File size: 264773 bytes
Release date: 2021-03-06
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