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/impl/ThrowableProxyHelper.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.impl;

import org.apache.logging.log4j.core.util.Loader;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.LoaderUtil;

import java.net.URL;
import java.security.CodeSource;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Stack;

/**
 * {@link ThrowableProxyHelper} provides utilities required to initialize a new {@link ThrowableProxy}
 * instance.
 */
class ThrowableProxyHelper {

    static final ThrowableProxy[] EMPTY_THROWABLE_PROXY_ARRAY = new ThrowableProxy[0];

    private ThrowableProxyHelper() {
        // Utility Class
    }

    /**
     * Cached StackTracePackageElement and ClassLoader.
     * <p>
     * Consider this class private.
     * </p>
     */
    static final class CacheEntry {
        private final ExtendedClassInfo element;
        private final ClassLoader loader;

        private CacheEntry(final ExtendedClassInfo element, final ClassLoader loader) {
            this.element = element;
            this.loader = loader;
        }
    }

    /**
     * Resolve all the stack entries in this stack trace that are not common with the parent.
     *
     * @param src        Instance for which to build an extended stack trace.
     * @param stack      The callers Class stack.
     * @param map        The cache of CacheEntry objects.
     * @param rootTrace  The first stack trace resolve or null.
     * @param stackTrace The stack trace being resolved.
     * @return The StackTracePackageElement array.
     */
    static ExtendedStackTraceElement[] toExtendedStackTrace(
            final ThrowableProxy src,
            final Stack<Class<?>> stack, final Map<String, CacheEntry> map,
            final StackTraceElement[] rootTrace,
            final StackTraceElement[] stackTrace) {
        int stackLength;
        if (rootTrace != null) {
            int rootIndex = rootTrace.length - 1;
            int stackIndex = stackTrace.length - 1;
            while (rootIndex >= 0 && stackIndex >= 0 && rootTrace[rootIndex].equals(stackTrace[stackIndex])) {
                --rootIndex;
                --stackIndex;
            }
            src.setCommonElementCount(stackTrace.length - 1 - stackIndex);
            stackLength = stackIndex + 1;
        } else {
            src.setCommonElementCount(0);
            stackLength = stackTrace.length;
        }
        final ExtendedStackTraceElement[] extStackTrace = new ExtendedStackTraceElement[stackLength];
        Class<?> clazz = stack.isEmpty() ? null : stack.peek();
        ClassLoader lastLoader = null;
        for (int i = stackLength - 1; i >= 0; --i) {
            final StackTraceElement stackTraceElement = stackTrace[i];
            final String className = stackTraceElement.getClassName();
            // The stack returned from getCurrentStack may be missing entries for java.lang.reflect.Method.invoke()
            // and its implementation. The Throwable might also contain stack entries that are no longer
            // present as those methods have returned.
            ExtendedClassInfo extClassInfo;
            if (clazz != null && className.equals(clazz.getName())) {
                final CacheEntry entry = toCacheEntry(clazz, true);
                extClassInfo = entry.element;
                lastLoader = entry.loader;
                stack.pop();
                clazz = stack.isEmpty() ? null : stack.peek();
            } else {
                final CacheEntry cacheEntry = map.get(className);
                if (cacheEntry != null) {
                    final CacheEntry entry = cacheEntry;
                    extClassInfo = entry.element;
                    if (entry.loader != null) {
                        lastLoader = entry.loader;
                    }
                } else {
                    final CacheEntry entry = toCacheEntry(ThrowableProxyHelper.loadClass(lastLoader, className), false);
                    extClassInfo = entry.element;
                    map.put(className, entry);
                    if (entry.loader != null) {
                        lastLoader = entry.loader;
                    }
                }
            }
            extStackTrace[i] = new ExtendedStackTraceElement(stackTraceElement, extClassInfo);
        }
        return extStackTrace;
    }

    static ThrowableProxy[] toSuppressedProxies(final Throwable thrown, Set<Throwable> suppressedVisited) {
        try {
            final Throwable[] suppressed = thrown.getSuppressed();
            if (suppressed == null || suppressed.length == 0) {
                return EMPTY_THROWABLE_PROXY_ARRAY;
            }
            final List<ThrowableProxy> proxies = new ArrayList<>(suppressed.length);
            if (suppressedVisited == null) {
                suppressedVisited = new HashSet<>(suppressed.length);
            }
            for (int i = 0; i < suppressed.length; i++) {
                final Throwable candidate = suppressed[i];
                if (suppressedVisited.add(candidate)) {
                    proxies.add(new ThrowableProxy(candidate, suppressedVisited));
                }
            }
            return proxies.toArray(new ThrowableProxy[proxies.size()]);
        } catch (final Exception e) {
            StatusLogger.getLogger().error(e);
        }
        return null;
    }

    /**
     * Construct the CacheEntry from the Class's information.
     *
     * @param callerClass       The Class.
     * @param exact             True if the class was obtained via Reflection.getCallerClass.
     * @return The CacheEntry.
     */
    private static CacheEntry toCacheEntry(final Class<?> callerClass, final boolean exact) {
        String location = "?";
        String version = "?";
        ClassLoader lastLoader = null;
        if (callerClass != null) {
            try {
                final CodeSource source = callerClass.getProtectionDomain().getCodeSource();
                if (source != null) {
                    final URL locationURL = source.getLocation();
                    if (locationURL != null) {
                        final String str = locationURL.toString().replace('\\', '/');
                        int index = str.lastIndexOf("/");
                        if (index >= 0 && index == str.length() - 1) {
                            index = str.lastIndexOf("/", index - 1);
                        }
                        location = str.substring(index + 1);
                    }
                }
            } catch (final Exception ex) {
                // Ignore the exception.
            }
            final Package pkg = callerClass.getPackage();
            if (pkg != null) {
                final String ver = pkg.getImplementationVersion();
                if (ver != null) {
                    version = ver;
                }
            }
            try {
                lastLoader = callerClass.getClassLoader();
            } catch (final SecurityException e) {
                lastLoader = null;
            }
        }
        return new CacheEntry(new ExtendedClassInfo(exact, location, version), lastLoader);
    }


    /**
     * Loads classes not located via Reflection.getCallerClass.
     *
     * @param lastLoader The ClassLoader that loaded the Class that called this Class.
     * @param className  The name of the Class.
     * @return The Class object for the Class or null if it could not be located.
     */
    private static Class<?> loadClass(final ClassLoader lastLoader, final String className) {
        // XXX: this is overly complicated
        Class<?> clazz;
        if (lastLoader != null) {
            try {
                clazz = lastLoader.loadClass(className);
                if (clazz != null) {
                    return clazz;
                }
            } catch (final Throwable ignore) {
                // Ignore exception.
            }
        }
        try {
            clazz = LoaderUtil.loadClass(className);
        } catch (final ClassNotFoundException | NoClassDefFoundError e) {
            return loadClass(className);
        } catch (final SecurityException e) {
            return null;
        }
        return clazz;
    }

    private static Class<?> loadClass(final String className) {
        try {
            return Loader.loadClass(className, ThrowableProxyHelper.class.getClassLoader());
        } catch (final ClassNotFoundException | NoClassDefFoundError | SecurityException e) {
            return null;
        }
    }
}

⏎ org/apache/logging/log4j/core/impl/ThrowableProxyHelper.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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