Source Code for Apache Log4j Core Implementation

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.

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org/apache/logging/log4j/core/config/plugins/util/PluginManager.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.util;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.Strings;

import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 * Loads and manages all the plugins.
 */
public class PluginManager {

    private static final CopyOnWriteArrayList<String> PACKAGES = new CopyOnWriteArrayList<>();
    private static final String LOG4J_PACKAGES = "org.apache.logging.log4j.core";

    private static final Logger LOGGER = StatusLogger.getLogger();

    private Map<String, PluginType<?>> plugins = new HashMap<>();
    private final String category;

    /**
     * Constructs a PluginManager for the plugin category name given.
     *
     * @param category The plugin category name.
     */
    public PluginManager(final String category) {
        this.category = category;
    }

    /**
     * Process annotated plugins.
     *
     * @deprecated Use {@link org.apache.logging.log4j.core.config.plugins.processor.PluginProcessor} instead. To do so,
     *             simply include {@code log4j-core} in your dependencies and make sure annotation processing is not
     *             disabled. By default, supported Java compilers will automatically use that plugin processor provided
     *             {@code log4j-core} is on the classpath.
     */
    @Deprecated
    // use PluginProcessor instead
    public static void main(final String[] args) {
        System.err.println("ERROR: this tool is superseded by the annotation processor included in log4j-core.");
        System.err.println("If the annotation processor does not work for you, please see the manual page:");
        System.err.println("http://logging.apache.org/log4j/2.x/manual/configuration.html#ConfigurationSyntax");
        System.exit(-1);
    }

    /**
     * Adds a package name to be scanned for plugins. Must be invoked prior to plugins being collected.
     *
     * @param p The package name. Ignored if {@code null} or empty.
     */
    public static void addPackage(final String p) {
        if (Strings.isBlank(p)) {
            return;
        }
        PACKAGES.addIfAbsent(p);
    }

    /**
     * Adds a list of package names to be scanned for plugins. Convenience method for {@link #addPackage(String)}.
     *
     * @param packages collection of package names to add. Empty and null package names are ignored.
     */
    public static void addPackages(final Collection<String> packages) {
        for (final String pkg : packages) {
            if (Strings.isNotBlank(pkg)) {
                PACKAGES.addIfAbsent(pkg);
            }
        }
    }

    /**
     * Returns the type of a specified plugin.
     *
     * @param name The name of the plugin.
     * @return The plugin's type.
     */
    public PluginType<?> getPluginType(final String name) {
        return plugins.get(name.toLowerCase());
    }

    /**
     * Returns all the matching plugins.
     *
     * @return A Map containing the name of the plugin and its type.
     */
    public Map<String, PluginType<?>> getPlugins() {
        return plugins;
    }

    /**
     * Locates all the plugins.
     */
    public void collectPlugins() {
        collectPlugins(null);
    }

    /**
     * Locates all the plugins including search of specific packages. Warns about name collisions.
     *
     * @param packages the list of packages to scan for plugins
     * @since 2.1
     */
    public void collectPlugins(final List<String> packages) {
        final String categoryLowerCase = category.toLowerCase();
        final Map<String, PluginType<?>> newPlugins = new LinkedHashMap<>();

        // First, iterate the Log4j2Plugin.dat files found in the main CLASSPATH
        Map<String, List<PluginType<?>>> builtInPlugins = PluginRegistry.getInstance().loadFromMainClassLoader();
        if (builtInPlugins.isEmpty()) {
            // If we didn't find any plugins above, someone must have messed with the log4j-core.jar.
            // Search the standard package in the hopes we can find our core plugins.
            builtInPlugins = PluginRegistry.getInstance().loadFromPackage(LOG4J_PACKAGES);
        }
        mergeByName(newPlugins, builtInPlugins.get(categoryLowerCase));

        // Next, iterate any Log4j2Plugin.dat files from OSGi Bundles
        for (final Map<String, List<PluginType<?>>> pluginsByCategory : PluginRegistry.getInstance().getPluginsByCategoryByBundleId().values()) {
            mergeByName(newPlugins, pluginsByCategory.get(categoryLowerCase));
        }

        // Next iterate any packages passed to the static addPackage method.
        for (final String pkg : PACKAGES) {
            mergeByName(newPlugins, PluginRegistry.getInstance().loadFromPackage(pkg).get(categoryLowerCase));
        }
        // Finally iterate any packages provided in the configuration (note these can be changed at runtime).
        if (packages != null) {
            for (final String pkg : packages) {
                mergeByName(newPlugins, PluginRegistry.getInstance().loadFromPackage(pkg).get(categoryLowerCase));
            }
        }

        LOGGER.debug("PluginManager '{}' found {} plugins", category, newPlugins.size());

        plugins = newPlugins;
    }

    private static void mergeByName(final Map<String, PluginType<?>> newPlugins, final List<PluginType<?>> plugins) {
        if (plugins == null) {
            return;
        }
        for (final PluginType<?> pluginType : plugins) {
            final String key = pluginType.getKey();
            final PluginType<?> existing = newPlugins.get(key);
            if (existing == null) {
                newPlugins.put(key, pluginType);
            } else if (!existing.getPluginClass().equals(pluginType.getPluginClass())) {
                LOGGER.warn("Plugin [{}] is already mapped to {}, ignoring {}",
                    key, existing.getPluginClass(), pluginType.getPluginClass());
            }
        }
    }
}

org/apache/logging/log4j/core/config/plugins/util/PluginManager.java

 

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2015-11-03, 51141👍, 0💬