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/spi/ExtendedLogger.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.spi;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.message.Message;
import org.apache.logging.log4j.util.MessageSupplier;
import org.apache.logging.log4j.util.Supplier;

/**
 * Extends the {@code Logger} interface with methods that facilitate implementing or extending {@code Logger}s. Users
 * should not need to use this interface.
 */
public interface ExtendedLogger extends Logger {

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The Message.
     * @param t A Throwable.
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, Message message, Throwable t);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param t A Throwable.
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, CharSequence message, Throwable t);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param t A Throwable.
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, Object message, Throwable t);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @return True if logging is enabled, false otherwise.
     * @param t the exception to log, including its stack trace.
     */
    boolean isEnabled(Level level, Marker marker, String message, Throwable t);

    /**
     * Determine if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param params The parameters.
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object... params);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1, Object p2);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1, Object p2, Object p3);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1, Object p2, Object p3,
            Object p4);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1, Object p2, Object p3,
            Object p4, Object p5);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @param p6 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1, Object p2, Object p3,
            Object p4, Object p5, Object p6);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @param p6 the message parameters
     * @param p7 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1, Object p2, Object p3,
            Object p4, Object p5, Object p6, Object p7);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @param p6 the message parameters
     * @param p7 the message parameters
     * @param p8 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1, Object p2, Object p3,
            Object p4, Object p5, Object p6, Object p7, Object p8);

    /**
     * Determines if logging is enabled.
     *
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @param p6 the message parameters
     * @param p7 the message parameters
     * @param p8 the message parameters
     * @param p9 the message parameters
     * @return True if logging is enabled, false otherwise.
     */
    boolean isEnabled(Level level, Marker marker, String message, Object p0, Object p1, Object p2, Object p3,
            Object p4, Object p5, Object p6, Object p7, Object p8, Object p9);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The Message.
     * @param t the exception to log, including its stack trace.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, Message message, Throwable t);

    /**
     * Logs a CharSequence message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The CharSequence message.
     * @param t the exception to log, including its stack trace.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, CharSequence message, Throwable t);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param t the exception to log, including its stack trace.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, Object message, Throwable t);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     * @param t the exception to log, including its stack trace.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Throwable t);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param params The message parameters.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object... params);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1, Object p2);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1, Object p2,
            Object p3);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1, Object p2,
            Object p3, Object p4);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1, Object p2,
            Object p3, Object p4, Object p5);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @param p6 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1, Object p2,
            Object p3, Object p4, Object p5, Object p6);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @param p6 the message parameters
     * @param p7 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1, Object p2,
            Object p3, Object p4, Object p5, Object p6, Object p7);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @param p6 the message parameters
     * @param p7 the message parameters
     * @param p8 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1, Object p2,
            Object p3, Object p4, Object p5, Object p6, Object p7, Object p8);

    /**
     * Logs a message if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param p0 the message parameters
     * @param p1 the message parameters
     * @param p2 the message parameters
     * @param p3 the message parameters
     * @param p4 the message parameters
     * @param p5 the message parameters
     * @param p6 the message parameters
     * @param p7 the message parameters
     * @param p8 the message parameters
     * @param p9 the message parameters
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Object p0, Object p1, Object p2,
            Object p3, Object p4, Object p5, Object p6, Object p7, Object p8, Object p9);

        /**
         * Always logs a message at the specified level. It is the responsibility of the caller to ensure the specified
         * level is enabled.
         *
         * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
         *            method when location information needs to be logged.
         * @param level The logging Level to check.
         * @param marker A Marker or null.
         * @param message The Message.
         * @param t the exception to log, including its stack trace.
         */
    void logMessage(String fqcn, Level level, Marker marker, Message message, Throwable t);

    /**
     * Logs a message which is only to be constructed if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param msgSupplier A function, which when called, produces the desired log message.
     * @param t the exception to log, including its stack trace.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, MessageSupplier msgSupplier, Throwable t);

    /**
     * Logs a message whose parameters are only to be constructed if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param message The message format.
     * @param paramSuppliers An array of functions, which when called, produce the desired log message parameters.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, String message, Supplier<?>... paramSuppliers);

    /**
     * Logs a message which is only to be constructed if the specified level is active.
     *
     * @param fqcn The fully qualified class name of the logger entry point, used to determine the caller class and
     *            method when location information needs to be logged.
     * @param level The logging Level to check.
     * @param marker A Marker or null.
     * @param msgSupplier A function, which when called, produces the desired log message.
     * @param t the exception to log, including its stack trace.
     */
    void logIfEnabled(String fqcn, Level level, Marker marker, Supplier<?> msgSupplier, Throwable t);

}

⏎ org/apache/logging/log4j/spi/ExtendedLogger.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
Download 

⇒ Source Code for Apache Log4j Core Implementation

⇐ Downloading Apache Log4j Binary Package

⇑ Downloading and Reviewing Apache Log4j Packages

⇑⇑ FAQ for Apache Log4j