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/plugins/visitors/AbstractPluginVisitor.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.plugins.visitors;

import java.lang.annotation.Annotation;
import java.lang.reflect.Member;
import java.util.Map;
import java.util.Objects;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.config.plugins.convert.TypeConverters;
import org.apache.logging.log4j.core.lookup.StrSubstitutor;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.Strings;

/**
 * Base class for PluginVisitor implementations. Provides convenience methods as well as all method implementations
 * other than the {@code visit} method.
 *
 * @param <A> the Plugin annotation type.
 */
public abstract class AbstractPluginVisitor<A extends Annotation> implements PluginVisitor<A> {

    /** Status logger. */
    protected static final Logger LOGGER = StatusLogger.getLogger();

    /**
     *
     */
    protected final Class<A> clazz;
    /**
     *
     */
    protected A annotation;
    /**
     *
     */
    protected String[] aliases;
    /**
     *
     */
    protected Class<?> conversionType;
    /**
     *
     */
    protected StrSubstitutor substitutor;
    /**
     *
     */
    protected Member member;

    /**
     * This constructor must be overridden by implementation classes as a no-arg constructor.
     *
     * @param clazz the annotation class this PluginVisitor is for.
     */
    protected AbstractPluginVisitor(final Class<A> clazz) {
        this.clazz = clazz;
    }

    @SuppressWarnings("unchecked")
    @Override
    public PluginVisitor<A> setAnnotation(final Annotation anAnnotation) {
        final Annotation a = Objects.requireNonNull(anAnnotation, "No annotation was provided");
        if (this.clazz.isInstance(a)) {
            this.annotation = (A) a;
        }
        return this;
    }

    @Override
    public PluginVisitor<A> setAliases(final String... someAliases) {
        this.aliases = someAliases;
        return this;
    }

    @Override
    public PluginVisitor<A> setConversionType(final Class<?> aConversionType) {
        this.conversionType = Objects.requireNonNull(aConversionType, "No conversion type class was provided");
        return this;
    }

    @Override
    public PluginVisitor<A> setStrSubstitutor(final StrSubstitutor aSubstitutor) {
        this.substitutor = Objects.requireNonNull(aSubstitutor, "No StrSubstitutor was provided");
        return this;
    }

    @Override
    public PluginVisitor<A> setMember(final Member aMember) {
        this.member = aMember;
        return this;
    }

    /**
     * Removes an Entry from a given Map using a key name and aliases for that key. Keys are case-insensitive.
     *
     * @param attributes the Map to remove an Entry from.
     * @param name       the key name to look up.
     * @param aliases    optional aliases of the key name to look up.
     * @return the value corresponding to the given key or {@code null} if nonexistent.
     */
    protected static String removeAttributeValue(final Map<String, String> attributes,
                                                 final String name,
                                                 final String... aliases) {
        for (final Map.Entry<String, String> entry : attributes.entrySet()) {
            final String key = entry.getKey();
            final String value = entry.getValue();
            if (key.equalsIgnoreCase(name)) {
                attributes.remove(key);
                return value;
            }
            if (aliases != null) {
                for (final String alias : aliases) {
                    if (key.equalsIgnoreCase(alias)) {
                        attributes.remove(key);
                        return value;
                    }
                }
            }
        }
        return null;
    }

    /**
     * Converts the given value into the configured type falling back to the provided default value.
     *
     * @param value        the value to convert.
     * @param defaultValue the fallback value to use in case of no value or an error.
     * @return the converted value whether that be based on the given value or the default value.
     */
    protected Object convert(final String value, final Object defaultValue) {
        if (defaultValue instanceof String) {
            return TypeConverters.convert(value, this.conversionType, Strings.trimToNull((String) defaultValue));
        }
        return TypeConverters.convert(value, this.conversionType, defaultValue);
    }
}

⏎ org/apache/logging/log4j/core/config/plugins/visitors/AbstractPluginVisitor.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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