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/config/AppenderControl.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.config;

import java.util.Objects;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AppenderLoggingException;
import org.apache.logging.log4j.core.filter.AbstractFilterable;
import org.apache.logging.log4j.core.filter.Filterable;
import org.apache.logging.log4j.util.PerformanceSensitive;

/**
 * Wraps an {@link Appender} with details an appender implementation shouldn't need to know about.
 */
public class AppenderControl extends AbstractFilterable {

    private final ThreadLocal<AppenderControl> recursive = new ThreadLocal<>();
    private final Appender appender;
    private final Level level;
    private final int intLevel;
    private final String appenderName;

    /**
     * Constructor.
     *
     * @param appender The target Appender.
     * @param level the Level to filter on.
     * @param filter the Filter(s) to apply.
     */
    public AppenderControl(final Appender appender, final Level level, final Filter filter) {
        super(filter);
        this.appender = appender;
        this.appenderName = appender.getName();
        this.level = level;
        this.intLevel = level == null ? Level.ALL.intLevel() : level.intLevel();
        start();
    }

    /**
     * Returns the name the appender had when this AppenderControl was constructed.
     *
     * @return the appender name
     */
    public String getAppenderName() {
        return appenderName;
    }

    /**
     * Returns the Appender.
     *
     * @return the Appender.
     */
    public Appender getAppender() {
        return appender;
    }

    /**
     * Call the appender.
     *
     * @param event The event to process.
     */
    public void callAppender(final LogEvent event) {
        if (shouldSkip(event)) {
            return;
        }
        callAppenderPreventRecursion(event);
    }

    private boolean shouldSkip(final LogEvent event) {
        return isFilteredByAppenderControl(event) || isFilteredByLevel(event) || isRecursiveCall();
    }

    @PerformanceSensitive
    private boolean isFilteredByAppenderControl(final LogEvent event) {
        final Filter filter = getFilter();
        return filter != null && Filter.Result.DENY == filter.filter(event);
    }

    @PerformanceSensitive
    private boolean isFilteredByLevel(final LogEvent event) {
        return level != null && intLevel < event.getLevel().intLevel();
    }

    @PerformanceSensitive
    private boolean isRecursiveCall() {
        if (recursive.get() != null) {
            appenderErrorHandlerMessage("Recursive call to appender ");
            return true;
        }
        return false;
    }

    private String appenderErrorHandlerMessage(final String prefix) {
        final String result = createErrorMsg(prefix);
        appender.getHandler().error(result);
        return result;
    }

    private void callAppenderPreventRecursion(final LogEvent event) {
        try {
            recursive.set(this);
            callAppender0(event);
        } finally {
            recursive.set(null);
        }
    }

    private void callAppender0(final LogEvent event) {
        ensureAppenderStarted();
        if (!isFilteredByAppender(event)) {
            tryCallAppender(event);
        }
    }

    private void ensureAppenderStarted() {
        if (!appender.isStarted()) {
            handleError("Attempted to append to non-started appender ");
        }
    }

    private void handleError(final String prefix) {
        final String msg = appenderErrorHandlerMessage(prefix);
        if (!appender.ignoreExceptions()) {
            throw new AppenderLoggingException(msg);
        }
    }

    private String createErrorMsg(final String prefix) {
        return prefix + appender.getName();
    }

    private boolean isFilteredByAppender(final LogEvent event) {
        return appender instanceof Filterable && ((Filterable) appender).isFiltered(event);
    }

    private void tryCallAppender(final LogEvent event) {
        try {
            appender.append(event);
        } catch (final RuntimeException error) {
            handleAppenderError(event, error);
        } catch (final Exception error) {
            handleAppenderError(event, new AppenderLoggingException(error));
        }
    }

    private void handleAppenderError(final LogEvent event, final RuntimeException ex) {
        appender.getHandler().error(createErrorMsg("An exception occurred processing Appender "), event, ex);
        if (!appender.ignoreExceptions()) {
            throw ex;
        }
    }

    // AppenderControl is a helper object whose purpose is to make it
    // easier for LoggerConfig to manage and invoke Appenders.
    // LoggerConfig manages Appenders by their name. To facilitate this,
    // two AppenderControl objects are considered equal if and only
    // if they have the same appender name.
    @Override
    public boolean equals(final Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof AppenderControl)) {
            return false;
        }
        final AppenderControl other = (AppenderControl) obj;
        return Objects.equals(appenderName, other.appenderName);
    }

    @Override
    public int hashCode() {
        return appenderName.hashCode();
    }

    @Override
    public String toString() {
        return super.toString() + "[appender=" + appender + ", appenderName=" + appenderName + ", level=" + level
                + ", intLevel=" + intLevel + ", recursive=" + recursive + ", filter=" + getFilter() + "]";
    }
}

⏎ org/apache/logging/log4j/core/config/AppenderControl.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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