/*
    * 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.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.CopyOnWriteArrayList;
  
  import org.apache.logging.log4j.Level;
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.core.Appender;
  import org.apache.logging.log4j.core.Filter;
  import org.apache.logging.log4j.core.Layout;
  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.appender.AsyncAppender;
  import org.apache.logging.log4j.core.appender.ConsoleAppender;
  import org.apache.logging.log4j.core.async.AsyncLoggerConfig;
  import org.apache.logging.log4j.core.async.AsyncLoggerContextSelector;
  import org.apache.logging.log4j.core.config.plugins.util.PluginBuilder;
  import org.apache.logging.log4j.core.config.plugins.util.PluginManager;
  import org.apache.logging.log4j.core.config.plugins.util.PluginType;
  import org.apache.logging.log4j.core.filter.AbstractFilterable;
  import org.apache.logging.log4j.core.impl.Log4jContextFactory;
  import org.apache.logging.log4j.core.layout.PatternLayout;
  import org.apache.logging.log4j.core.lookup.Interpolator;
  import org.apache.logging.log4j.core.lookup.MapLookup;
  import org.apache.logging.log4j.core.lookup.StrLookup;
  import org.apache.logging.log4j.core.lookup.StrSubstitutor;
  import org.apache.logging.log4j.core.net.Advertiser;
  import org.apache.logging.log4j.core.selector.ContextSelector;
  import org.apache.logging.log4j.core.util.Assert;
  import org.apache.logging.log4j.core.util.Constants;
  import org.apache.logging.log4j.core.util.Loader;
  import org.apache.logging.log4j.core.util.NameUtil;
  import org.apache.logging.log4j.spi.LoggerContextFactory;
  import org.apache.logging.log4j.util.PropertiesUtil;
  
  /**
   * The base Configuration. Many configuration implementations will extend this class.
   */
  public abstract class AbstractConfiguration extends AbstractFilterable implements Configuration {
  
      private static final long serialVersionUID = 1L;
  
      private static final int BUF_SIZE = 16384;
  
      /**
       * The root node of the configuration.
       */
      protected Node rootNode;
  
      /**
       * Listeners for configuration changes.
       */
      protected final List<ConfigurationListener> listeners = new CopyOnWriteArrayList<ConfigurationListener>();
  
      /**
       * The ConfigurationMonitor that checks for configuration changes.
       */
      protected ConfigurationMonitor monitor = new DefaultConfigurationMonitor();
  
      /**
       * The Advertiser which exposes appender configurations to external systems.
       */
      private Advertiser advertiser = new DefaultAdvertiser();
      private Node advertiserNode = null;
      private Object advertisement;
  
      /**
       *
       */
      protected boolean isShutdownHookEnabled = true;
      private String name;
     private ConcurrentMap<String, Appender> appenders = new ConcurrentHashMap<String, Appender>();
     private ConcurrentMap<String, LoggerConfig> loggers = new ConcurrentHashMap<String, LoggerConfig>();
     private List<CustomLevelConfig> customLevels = Collections.emptyList();
     private final ConcurrentMap<String, String> properties = new ConcurrentHashMap<String, String>();
     private final StrLookup tempLookup = new Interpolator(properties);
     private final StrSubstitutor subst = new StrSubstitutor(tempLookup);
     private LoggerConfig root = new LoggerConfig();
     private final ConcurrentMap<String, Object> componentMap = new ConcurrentHashMap<String, Object>();
     protected final List<String> pluginPackages = new ArrayList<String>();
     protected PluginManager pluginManager;
     private final ConfigurationSource configurationSource;
 
     /**
      * Constructor.
      */
     protected AbstractConfiguration(final ConfigurationSource configurationSource) {
         this.configurationSource = Assert.requireNonNull(configurationSource, "configurationSource is null");
         componentMap.put(Configuration.CONTEXT_PROPERTIES, properties);
         pluginManager = new PluginManager(Node.CATEGORY);
         rootNode = new Node();
     }
 
     @Override
     public ConfigurationSource getConfigurationSource() {
         return configurationSource;
     }
 
     @Override
     public List<String> getPluginPackages() {
         return pluginPackages;
     }
 
     @Override
     public Map<String, String> getProperties() {
         return properties;
     }
 
     /**
      * Initialize the configuration.
      */
     @Override
     public void start() {
         LOGGER.debug("Starting configuration {}", this);
         this.setStarting();
         pluginManager.collectPlugins(pluginPackages);
         final PluginManager levelPlugins = new PluginManager(Level.CATEGORY);
         levelPlugins.collectPlugins(pluginPackages);
         final Map<String, PluginType<?>> plugins = levelPlugins.getPlugins();
         if (plugins != null) {
             for (final PluginType<?> type : plugins.values()) {
                 try {
                     // Cause the class to be initialized if it isn't already.
                     Loader.initializeClass(type.getPluginClass().getName(), type.getPluginClass().getClassLoader());
                 } catch (final Exception e) {
                     LOGGER.error("Unable to initialize {} due to {}", type.getPluginClass().getName(), e.getClass()
                             .getSimpleName(), e);
                 }
             }
         }
         setup();
         setupAdvertisement();
         doConfigure();
         final Set<LoggerConfig> alreadyStarted = new HashSet<LoggerConfig>();
         for (final LoggerConfig logger : loggers.values()) {
             logger.start();
             alreadyStarted.add(logger);
         }
         for (final Appender appender : appenders.values()) {
             appender.start();
         }
         if (!alreadyStarted.contains(root)) { // LOG4J2-392
             root.start(); // LOG4J2-336
         }
         super.start();
         LOGGER.debug("Started configuration {} OK.", this);
     }
 
     /**
      * Tear down the configuration.
      */
     @Override
     public void stop() {
         this.setStopping();
         LOGGER.trace("Stopping {}...", this);
 
         // LOG4J2-392 first stop AsyncLogger Disruptor thread
         final LoggerContextFactory factory = LogManager.getFactory();
         if (factory instanceof Log4jContextFactory) {
             final ContextSelector selector = ((Log4jContextFactory) factory).getSelector();
             if (selector instanceof AsyncLoggerContextSelector) { // all loggers are async
                 // TODO until LOG4J2-493 is fixed we can only stop AsyncLogger once!
                 // but LoggerContext.setConfiguration will call config.stop()
                 // every time the configuration changes...
                 //
                 // Uncomment the line below after LOG4J2-493 is fixed
                 //AsyncLogger.stop();
                 //LOGGER.trace("AbstractConfiguration stopped AsyncLogger disruptor.");
             }
         }
         // similarly, first stop AsyncLoggerConfig Disruptor thread(s)
         final Set<LoggerConfig> alreadyStopped = new HashSet<LoggerConfig>();
         int asyncLoggerConfigCount = 0;
         for (final LoggerConfig logger : loggers.values()) {
             if (logger instanceof AsyncLoggerConfig) {
                 // LOG4J2-520, LOG4J2-392:
                 // Important: do not clear appenders until after all AsyncLoggerConfigs
                 // have been stopped! Stopping the last AsyncLoggerConfig will
                 // shut down the disruptor and wait for all enqueued events to be processed.
                 // Only *after this* the appenders can be cleared or events will be lost.
                 logger.stop();
                 asyncLoggerConfigCount++;
                 alreadyStopped.add(logger);
             }
         }
         if (root instanceof AsyncLoggerConfig & !alreadyStopped.contains(root)) { // LOG4J2-807
             root.stop();
             asyncLoggerConfigCount++;
             alreadyStopped.add(root);
         }
         LOGGER.trace("AbstractConfiguration stopped {} AsyncLoggerConfigs.", asyncLoggerConfigCount);
 
         // Stop the appenders in reverse order in case they still have activity.
         final Appender[] array = appenders.values().toArray(new Appender[appenders.size()]);
 
         // LOG4J2-511, LOG4J2-392 stop AsyncAppenders first
         int asyncAppenderCount = 0;
         for (int i = array.length - 1; i >= 0; --i) {
             if (array[i] instanceof AsyncAppender) {
                 array[i].stop();
                 asyncAppenderCount++;
             }
         }
         LOGGER.trace("AbstractConfiguration stopped {} AsyncAppenders.", asyncAppenderCount);
 
         int appenderCount = 0;
         for (int i = array.length - 1; i >= 0; --i) {
             if (array[i].isStarted()) { // then stop remaining Appenders
                 array[i].stop();
                 appenderCount++;
             }
         }
         LOGGER.trace("AbstractConfiguration stopped {} Appenders.", appenderCount);
 
         int loggerCount = 0;
         for (final LoggerConfig logger : loggers.values()) {
             // clear appenders, even if this logger is already stopped.
             logger.clearAppenders();
 
             // AsyncLoggerConfigHelper decreases its ref count when an AsyncLoggerConfig is stopped.
             // Stopping the same AsyncLoggerConfig twice results in an incorrect ref count and
             // the shared Disruptor may be shut down prematurely, resulting in NPE or other errors.
             if (alreadyStopped.contains(logger)) {
                 continue;
             }
             logger.stop();
             loggerCount++;
         }
         LOGGER.trace("AbstractConfiguration stopped {} Loggers.", loggerCount);
 
         // AsyncLoggerConfigHelper decreases its ref count when an AsyncLoggerConfig is stopped.
         // Stopping the same AsyncLoggerConfig twice results in an incorrect ref count and
         // the shared Disruptor may be shut down prematurely, resulting in NPE or other errors.
         if (!alreadyStopped.contains(root)) {
             root.stop();
         }
         super.stop();
         if (advertiser != null && advertisement != null) {
             advertiser.unadvertise(advertisement);
         }
         LOGGER.debug("Stopped {} OK", this);
     }
 
     @Override
     public boolean isShutdownHookEnabled() {
         return isShutdownHookEnabled;
     }
 
     protected void setup() {
     }
 
     protected Level getDefaultStatus() {
         final String statusLevel = PropertiesUtil.getProperties().getStringProperty(Constants.LOG4J_DEFAULT_STATUS_LEVEL,
             Level.ERROR.name());
         try {
             return Level.toLevel(statusLevel);
         } catch (final Exception ex) {
             return Level.ERROR;
         }
     }
 
     protected void createAdvertiser(final String advertiserString, final ConfigurationSource configSource,
                                     final byte[] buffer, final String contentType) {
         if (advertiserString != null) {
             final Node node = new Node(null, advertiserString, null);
             final Map<String, String> attributes = node.getAttributes();
             attributes.put("content", new String(buffer));
             attributes.put("contentType", contentType);
             attributes.put("name", "configuration");
             if (configSource.getLocation() != null) {
                 attributes.put("location", configSource.getLocation());
             }
             advertiserNode = node;
         }
     }
 
     private void setupAdvertisement() {
         if (advertiserNode != null)
         {
             final String name = advertiserNode.getName();
             final PluginType<?> type = pluginManager.getPluginType(name);
             if (type != null)
             {
                 final Class<? extends Advertiser> clazz = type.getPluginClass().asSubclass(Advertiser.class);
                 try {
                     advertiser = clazz.newInstance();
                     advertisement = advertiser.advertise(advertiserNode.getAttributes());
                 } catch (final InstantiationException e) {
                     LOGGER.error("InstantiationException attempting to instantiate advertiser: {}", name, e);
                 } catch (final IllegalAccessException e) {
                     LOGGER.error("IllegalAccessException attempting to instantiate advertiser: {}", name, e);
                 }
             }
         }
     }
 
     @SuppressWarnings("unchecked")
     @Override
     public <T> T getComponent(final String name) {
         return (T) componentMap.get(name);
     }
 
     @Override
     public void addComponent(final String name, final Object obj) {
         componentMap.putIfAbsent(name, obj);
     }
 
     protected void doConfigure() {
         if (rootNode.hasChildren() && rootNode.getChildren().get(0).getName().equalsIgnoreCase("Properties")) {
             final Node first = rootNode.getChildren().get(0);
             createConfiguration(first, null);
             if (first.getObject() != null) {
                 subst.setVariableResolver((StrLookup) first.getObject());
             }
         } else {
             final Map<String, String> map = this.getComponent(CONTEXT_PROPERTIES);
             final StrLookup lookup = map == null ? null : new MapLookup(map);
             subst.setVariableResolver(new Interpolator(lookup, pluginPackages));
         }
 
         boolean setLoggers = false;
         boolean setRoot = false;
         for (final Node child : rootNode.getChildren()) {
             if (child.getName().equalsIgnoreCase("Properties")) {
                 if (tempLookup == subst.getVariableResolver()) {
                     LOGGER.error("Properties declaration must be the first element in the configuration");
                 }
                 continue;
             }
             createConfiguration(child, null);
             if (child.getObject() == null) {
                 continue;
             }
             if (child.getName().equalsIgnoreCase("Appenders")) {
                 appenders = child.getObject();
             } else if (child.isInstanceOf(Filter.class)) {
                 addFilter(child.getObject(Filter.class));
             } else if (child.getName().equalsIgnoreCase("Loggers")) {
                 final Loggers l = child.getObject();
                 loggers = l.getMap();
                 setLoggers = true;
                 if (l.getRoot() != null) {
                     root = l.getRoot();
                     setRoot = true;
                 }
             } else if (child.getName().equalsIgnoreCase("CustomLevels")) {
                 customLevels = child.getObject(CustomLevels.class).getCustomLevels();
             } else if (child.isInstanceOf(CustomLevelConfig.class)) {
                 final List<CustomLevelConfig> copy = new ArrayList<CustomLevelConfig>(customLevels);
                 copy.add(child.getObject(CustomLevelConfig.class));
                 customLevels = copy;
             } else {
                 LOGGER.error("Unknown object \"{}\" of type {} is ignored.", child.getName(),
                         child.getObject().getClass().getName());
             }
         }
 
         if (!setLoggers) {
             LOGGER.warn("No Loggers were configured, using default. Is the Loggers element missing?");
             setToDefault();
             return;
         } else if (!setRoot) {
             LOGGER.warn("No Root logger was configured, creating default ERROR-level Root logger with Console appender");
             setToDefault();
             // return; // LOG4J2-219: creating default root=ok, but don't exclude configured Loggers
         }
 
         for (final Map.Entry<String, LoggerConfig> entry : loggers.entrySet()) {
             final LoggerConfig l = entry.getValue();
             for (final AppenderRef ref : l.getAppenderRefs()) {
                 final Appender app = appenders.get(ref.getRef());
                 if (app != null) {
                     l.addAppender(app, ref.getLevel(), ref.getFilter());
                 } else {
                     LOGGER.error("Unable to locate appender {} for logger {}", ref.getRef(), l.getName());
                 }
             }
 
         }
 
         setParents();
     }
 
     private void setToDefault() {
         // TODO: reduce duplication between this method and DefaultConfiguration constructor
         setName(DefaultConfiguration.DEFAULT_NAME);
         final Layout<? extends Serializable> layout = PatternLayout.newBuilder()
             .withPattern(DefaultConfiguration.DEFAULT_PATTERN)
             .withConfiguration(this)
             .build();
         final Appender appender = ConsoleAppender.createDefaultAppenderForLayout(layout);
         appender.start();
         addAppender(appender);
         final LoggerConfig root = getRootLogger();
         root.addAppender(appender, null, null);
 
         final String levelName = PropertiesUtil.getProperties().getStringProperty(DefaultConfiguration.DEFAULT_LEVEL);
         final Level level = levelName != null && Level.getLevel(levelName) != null ?
             Level.getLevel(levelName) : Level.ERROR;
         root.setLevel(level);
     }
 
     /**
      * Set the name of the configuration.
      * @param name The name.
      */
     public void setName(final String name) {
         this.name = name;
     }
 
     /**
      * Returns the name of the configuration.
      * @return the name of the configuration.
      */
     @Override
     public String getName() {
         return name;
     }
 
     /**
      * Add a listener for changes on the configuration.
      * @param listener The ConfigurationListener to add.
      */
     @Override
     public void addListener(final ConfigurationListener listener) {
         listeners.add(listener);
     }
 
     /**
      * Remove a ConfigurationListener.
      * @param listener The ConfigurationListener to remove.
      */
     @Override
     public void removeListener(final ConfigurationListener listener) {
         listeners.remove(listener);
     }
 
     /**
      * Returns the Appender with the specified name.
      * @param name The name of the Appender.
      * @return the Appender with the specified name or null if the Appender cannot be located.
      */
     @Override
     public Appender getAppender(final String name) {
         return appenders.get(name);
     }
 
     /**
      * Returns a Map containing all the Appenders and their name.
      * @return A Map containing each Appender's name and the Appender object.
      */
     @Override
     public Map<String, Appender> getAppenders() {
         return appenders;
     }
 
     /**
      * Adds an Appender to the configuration.
      * @param appender The Appender to add.
      */
     @Override
     public void addAppender(final Appender appender) {
         appenders.putIfAbsent(appender.getName(), appender);
     }
 
     @Override
     public StrSubstitutor getStrSubstitutor() {
         return subst;
     }
 
     @Override
     public void setConfigurationMonitor(final ConfigurationMonitor monitor) {
         this.monitor = monitor;
     }
 
     @Override
     public ConfigurationMonitor getConfigurationMonitor() {
         return monitor;
     }
 
     @Override
     public void setAdvertiser(final Advertiser advertiser) {
         this.advertiser = advertiser;
     }
 
     @Override
     public Advertiser getAdvertiser() {
         return advertiser;
     }
 
     /**
      * Associates an Appender with a LoggerConfig. This method is synchronized in case a Logger with the
      * same name is being updated at the same time.
      *
      * Note: This method is not used when configuring via configuration. It is primarily used by
      * unit tests.
      * @param logger The Logger the Appender will be associated with.
      * @param appender The Appender.
      */
     @Override
     public synchronized void addLoggerAppender(final org.apache.logging.log4j.core.Logger logger,
                                                final Appender appender) {
         final String name = logger.getName();
         appenders.putIfAbsent(appender.getName(), appender);
         final LoggerConfig lc = getLoggerConfig(name);
         if (lc.getName().equals(name)) {
             lc.addAppender(appender, null, null);
         } else {
             final LoggerConfig nlc = new LoggerConfig(name, lc.getLevel(), lc.isAdditive());
             nlc.addAppender(appender, null, null);
             nlc.setParent(lc);
             loggers.putIfAbsent(name, nlc);
             setParents();
             logger.getContext().updateLoggers();
         }
     }
     /**
      * Associates a Filter with a LoggerConfig. This method is synchronized in case a Logger with the
      * same name is being updated at the same time.
      *
      * Note: This method is not used when configuring via configuration. It is primarily used by
      * unit tests.
      * @param logger The Logger the Fo;ter will be associated with.
      * @param filter The Filter.
      */
     @Override
     public synchronized void addLoggerFilter(final org.apache.logging.log4j.core.Logger logger, final Filter filter) {
         final String name = logger.getName();
         final LoggerConfig lc = getLoggerConfig(name);
         if (lc.getName().equals(name)) {
 
             lc.addFilter(filter);
         } else {
             final LoggerConfig nlc = new LoggerConfig(name, lc.getLevel(), lc.isAdditive());
             nlc.addFilter(filter);
             nlc.setParent(lc);
             loggers.putIfAbsent(name, nlc);
             setParents();
             logger.getContext().updateLoggers();
         }
     }
     /**
      * Marks a LoggerConfig as additive. This method is synchronized in case a Logger with the
      * same name is being updated at the same time.
      *
      * Note: This method is not used when configuring via configuration. It is primarily used by
      * unit tests.
      * @param logger The Logger the Appender will be associated with.
      * @param additive True if the LoggerConfig should be additive, false otherwise.
      */
     @Override
     public synchronized void setLoggerAdditive(final org.apache.logging.log4j.core.Logger logger,
                                                final boolean additive) {
         final String name = logger.getName();
         final LoggerConfig lc = getLoggerConfig(name);
         if (lc.getName().equals(name)) {
             lc.setAdditive(additive);
         } else {
             final LoggerConfig nlc = new LoggerConfig(name, lc.getLevel(), additive);
             nlc.setParent(lc);
             loggers.putIfAbsent(name, nlc);
             setParents();
             logger.getContext().updateLoggers();
         }
     }
 
     /**
      * Remove an Appender. First removes any associations between LoggerConfigs and the Appender, removes
      * the Appender from this appender list and then stops the appender. This method is synchronized in
      * case an Appender with the same name is being added during the removal.
      * @param name the name of the appender to remove.
      */
     public synchronized void removeAppender(final String name) {
         for (final LoggerConfig logger : loggers.values()) {
             logger.removeAppender(name);
         }
         final Appender app = appenders.remove(name);
 
         if (app != null) {
             app.stop();
         }
     }
 
     /*
      * (non-Javadoc)
      * @see org.apache.logging.log4j.core.config.Configuration#getCustomLevels()
      */
     @Override
     public List<CustomLevelConfig> getCustomLevels() {
         return Collections.unmodifiableList(customLevels);
     }
 
     /**
      * Locates the appropriate LoggerConfig for a Logger name. This will remove tokens from the
      * package name as necessary or return the root LoggerConfig if no other matches were found.
      * @param name The Logger name.
      * @return The located LoggerConfig.
      */
     @Override
     public LoggerConfig getLoggerConfig(final String name) {
         if (loggers.containsKey(name)) {
             return loggers.get(name);
         }
         String substr = name;
         while ((substr = NameUtil.getSubName(substr)) != null) {
             if (loggers.containsKey(substr)) {
                 return loggers.get(substr);
             }
         }
         return root;
     }
 
     /**
      * Returns the root Logger.
      * @return the root Logger.
      */
     public LoggerConfig getRootLogger() {
         return root;
     }
 
     /**
      * Returns a Map of all the LoggerConfigs.
      * @return a Map with each entry containing the name of the Logger and the LoggerConfig.
      */
     @Override
     public Map<String, LoggerConfig> getLoggers() {
         return Collections.unmodifiableMap(loggers);
     }
 
     /**
      * Returns the LoggerConfig with the specified name.
      * @param name The Logger name.
      * @return The LoggerConfig or null if no match was found.
      */
     public LoggerConfig getLogger(final String name) {
         return loggers.get(name);
     }
 
     /**
      * Add a loggerConfig. The LoggerConfig must already be configured with Appenders, Filters, etc.
      * After addLogger is called LoggerContext.updateLoggers must be called.
      *
      * @param name The name of the Logger.
      * @param loggerConfig The LoggerConfig.
      */
     @Override
     public synchronized void addLogger(final String name, final LoggerConfig loggerConfig) {
         loggers.putIfAbsent(name, loggerConfig);
         setParents();
     }
 
     /**
      * Remove a LoggerConfig.
      *
      * @param name The name of the Logger.
      */
     @Override
     public synchronized void removeLogger(final String name) {
         loggers.remove(name);
         setParents();
     }
 
     @Override
     public void createConfiguration(final Node node, final LogEvent event) {
         final PluginType<?> type = node.getType();
         if (type != null && type.isDeferChildren()) {
             node.setObject(createPluginObject(type, node, event));
         } else {
             for (final Node child : node.getChildren()) {
                 createConfiguration(child, event);
             }
 
             if (type == null) {
                 if (node.getParent() != null) {
                     LOGGER.error("Unable to locate plugin for {}", node.getName());
                 }
             } else {
                 node.setObject(createPluginObject(type, node, event));
             }
         }
     }
 
    /**
     * Invokes a static factory method to either create the desired object or to create a builder object that creates
     * the desired object. In the case of a factory method, it should be annotated with
     * {@link org.apache.logging.log4j.core.config.plugins.PluginFactory}, and each parameter should be annotated with
     * an appropriate plugin annotation depending on what that parameter describes. Parameters annotated with
     * {@link org.apache.logging.log4j.core.config.plugins.PluginAttribute} must be a type that can be converted from
     * a string using one of the {@link org.apache.logging.log4j.core.config.plugins.convert.TypeConverter TypeConverters}.
     * Parameters with {@link org.apache.logging.log4j.core.config.plugins.PluginElement} may be any plugin class or an
     * array of a plugin class. Collections and Maps are currently not supported, although the factory method that is
     * called can create these from an array.
     *
     * Plugins can also be created using a builder class that implements
     * {@link org.apache.logging.log4j.core.util.Builder}. In that case, a static method annotated with
     * {@link org.apache.logging.log4j.core.config.plugins.PluginBuilderAttribute} should create the builder class,
     * and the various fields in the builder class should be annotated similarly to the method parameters. However,
     * instead of using PluginAttribute, one should use
     * {@link org.apache.logging.log4j.core.config.plugins.PluginBuilderAttribute} where the default value can be
     * specified as the default field value instead of as an additional annotation parameter.
     *
     * In either case, there are also annotations for specifying a
     * {@link org.apache.logging.log4j.core.config.Configuration}
     * ({@link org.apache.logging.log4j.core.config.plugins.PluginConfiguration}) or a
     * {@link org.apache.logging.log4j.core.config.Node}
     * ({@link org.apache.logging.log4j.core.config.plugins.PluginNode}).
     *
     * Although the happy path works, more work still needs to be done to log incorrect
     * parameters. These will generally result in unhelpful InvocationTargetExceptions.
     *
     * @param type the type of plugin to create.
     * @param node the corresponding configuration node for this plugin to create.
     * @param event the LogEvent that spurred the creation of this plugin
     * @return the created plugin object or {@code null} if there was an error setting it up.
     * @see org.apache.logging.log4j.core.config.plugins.util.PluginBuilder
     * @see org.apache.logging.log4j.core.config.plugins.visitors.PluginVisitor
     * @see org.apache.logging.log4j.core.config.plugins.convert.TypeConverter
     */
     private Object createPluginObject(final PluginType<?> type, final Node node, final LogEvent event) {
         final Class<?> clazz = type.getPluginClass();
 
         if (Map.class.isAssignableFrom(clazz)) {
             try {
                 return createPluginMap(node);
             } catch (final Exception e) {
                 LOGGER.warn("Unable to create Map for {} of class {}", type.getElementName(), clazz, e);
             }
         }
 
         if (Collection.class.isAssignableFrom(clazz)) {
             try {
                 return createPluginCollection(node);
             } catch (final Exception e) {
                 LOGGER.warn("Unable to create List for {} of class {}", type.getElementName(), clazz, e);
             }
         }
 
         return new PluginBuilder(type)
                 .withConfiguration(this)
                 .withConfigurationNode(node)
                 .forLogEvent(event)
                 .build();
     }
 
     private static Map<String, ?> createPluginMap(final Node node) {
         final Map<String, Object> map = new LinkedHashMap<String, Object>();
         for (final Node child : node.getChildren()) {
             final Object object = child.getObject();
             map.put(child.getName(), object);
         }
         return map;
     }
 
     private static Collection<?> createPluginCollection(final Node node) {
         final List<Node> children = node.getChildren();
         final Collection<Object> list = new ArrayList<Object>(children.size());
         for (final Node child : children) {
             final Object object = child.getObject();
             list.add(object);
         }
         return list;
     }
 
     private void setParents() {
          for (final Map.Entry<String, LoggerConfig> entry : loggers.entrySet()) {
             final LoggerConfig logger = entry.getValue();
             String name = entry.getKey();
             if (!name.isEmpty()) {
                 final int i = name.lastIndexOf('.');
                 if (i > 0) {
                     name = name.substring(0, i);
                     LoggerConfig parent = getLoggerConfig(name);
                     if (parent == null) {
                         parent = root;
                     }
                     logger.setParent(parent);
                 } else {
                     logger.setParent(root);
                 }
             }
         }
     }
 
     /**
      * Reads an InputStream using buffered reads into a byte array buffer. The given InputStream will remain open
      * after invocation of this method.
      *
      * @param is the InputStream to read into a byte array buffer.
      * @return a byte array of the InputStream contents.
      * @throws IOException if the {@code read} method of the provided InputStream throws this exception.
      */
     protected static byte[] toByteArray(final InputStream is) throws IOException {
         final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
 
         int nRead;
         final byte[] data = new byte[BUF_SIZE];
 
         while ((nRead = is.read(data, 0, data.length)) != -1) {
             buffer.write(data, 0, nRead);
         }
 
         return buffer.toByteArray();
     }
 
 }