<?xml version="1.0"?>
<!--
    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.
-->

#set($dollar = '$')

<document xmlns="http://maven.apache.org/XDOC/2.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">
    <properties>
        <title>Configuring Log4j 2</title>
        <author email="rgoers@apache.org">Ralph Goers</author>
    </properties>

    <body>
      <section name="Configuration">
        #if (!$alignedFileName)
            #set ($isPDF = true)
        #else
            #set ($isPDF = false)
        #end
        <p>Inserting log requests into the application code requires a fair
          amount of planning and effort. Observation shows that approximately 4
          percent of code is dedicated to logging. Consequently, even moderately
          sized applications will have thousands of logging statements embedded
          within their code.  Given their number, it becomes imperative to
          manage these log statements without the need to modify them manually.
        </p>
        <p>
          Configuration of Log4j 2 can be accomplished in 1 of 4 ways:
        </p>
          <ol>
            <li>Through a configuration file written in XML, JSON, YAML, or properties format.</li>
            <li>Programmatically, by creating a ConfigurationFactory and Configuration implementation.</li>
            <li>Programmatically, by calling the APIs exposed in the Configuration interface to add
              components to the default configuration.</li>
            <li>Programmatically, by calling methods on the internal Logger class.</li>
          </ol>
        <p>
          This page focuses primarily on configuring Log4j through a configuration file. Information on
          programmatically configuring Log4j can be found at <a href="./extending.html">Extending Log4j 2</a>
          and <a href="customconfig.html">Programmatic Log4j Configuration</a>.
        </p>
        <p>
          Note that unlike Log4j 1.x, the public Log4j 2 API does not expose methods to add, modify or remove
          appenders and filters or manipulate the configuration in any way.
        </p>
        <a name="AutomaticConfiguration"/>
        <subsection name="Automatic Configuration">
          <p>
            Log4j has the ability to automatically configure itself during initialization.
            When Log4j starts it will locate all the ConfigurationFactory plugins and arrange them in weighted
            order from highest to lowest. As delivered, Log4j contains four ConfigurationFactory implementations:
            one for JSON, one for YAML, one for properties, and one for XML.
          </p>
            <ol>
              <li>Log4j will inspect the <code>"log4j.configurationFile"</code> system property and, if set,  will attempt to
                load the configuration using the <code>ConfigurationFactory</code> that matches the file
                extension.</li>
              <li>If no system property is set the properties ConfigurationFactory will look for
                <code>log4j2-test.properties</code> in the classpath.</li>
              <li>If no such file is found the YAML ConfigurationFactory will look for
                <code>log4j2-test.yaml</code> or <code>log4j2-test.yml</code> in the classpath.</li>
              <li>If no such file is found the JSON ConfigurationFactory will look for
                <code>log4j2-test.json</code> or <code>log4j2-test.jsn</code> in the classpath.</li>
              <li>If no such file is found the XML ConfigurationFactory will look for
                <code>log4j2-test.xml</code> in the classpath.</li>
              <li>If a test file cannot be located the properties ConfigurationFactory will look for
                <code>log4j2.properties</code> on the classpath.</li>
              <li>If a properties file cannot be located the YAML ConfigurationFactory will look for
                <code>log4j2.yaml</code> or <code>log4j2.yml</code> on the classpath.</li>
              <li>If a YAML file cannot be located the JSON ConfigurationFactory will look for
                <code>log4j2.json</code> or <code>log4j2.jsn</code> on the classpath.</li>
              <li>If a JSON file cannot be located the XML ConfigurationFactory will try to locate
                <code>log4j2.xml</code> on the classpath.</li>
              <li>If no configuration file could be located the <code>DefaultConfiguration</code> will
                be used. This will cause logging output to go to the console.</li>
            </ol>
          <p>An example application named <code>MyApp</code> that uses log4j can be used to illustrate how
            this is done.
          </p>
<pre class="prettyprint linenums"><![CDATA[
import com.foo.Bar;

// Import log4j classes.
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;

public class MyApp {

    // Define a static logger variable so that it references the
    // Logger instance named "MyApp".
    private static final Logger logger = LogManager.getLogger(MyApp.class);

    public static void main(final String... args) {

        // Set up a simple configuration that logs on the console.

        logger.trace("Entering application.");
        Bar bar = new Bar();
        if (!bar.doIt()) {
            logger.error("Didn't do it.");
        }
        logger.trace("Exiting application.");
    }
}
]]></pre>
          <p>
            <code>MyApp</code> begins by importing log4j related classes. It
            then defines a static logger variable with the name <code>MyApp</code>
            which happens to be the fully qualified name of the class.
          </p>
          <p>
            <code>MyApp</code> uses the <code>Bar</code> class defined in the package<code>com.foo</code>.
          </p>
<pre class="prettyprint linenums"><![CDATA[
package com.foo;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;

public class Bar {
  static final Logger logger = LogManager.getLogger(Bar.class.getName());

  public boolean doIt() {
    logger.entry();
    logger.error("Did it again!");
    return logger.exit(false);
  }
}
]]></pre>
          <p>
            Log4j will provide a default configuration if it cannot locate a configuration file. The default
            configuration, provided in the DefaultConfiguration class, will set up:
          </p>
            <ul>
              <li>A <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/appender/ConsoleAppender.html">ConsoleAppender</a>
                attached to the root logger.</li>
              <li>A <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/layout/PatternLayout.html">PatternLayout</a>
                set to the pattern "%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" attached to the ConsoleAppender</li>
            </ul>
          <p>
            Note that by default Log4j assigns the root logger to <code>Level.ERROR</code>.
          </p>
          <p>The output of MyApp would be similar to:
          </p>
<pre><![CDATA[
17:13:01.540 [main] ERROR com.foo.Bar - Did it again!
17:13:01.540 [main] ERROR MyApp - Didn't do it.
]]></pre>
          <p>
            As was described previously, Log4j will first attempt to configure itself from configuration files. A
            configuration equivalent to the default would look like:
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="Console"/>
    </Root>
  </Loggers>
</Configuration>
]]></pre>
          <p>
            Once the file above is placed into the classpath as log4j2.xml you will get results identical to
            those listed above. Changing the root level to trace will result in results similar to:
          </p>
          <pre><![CDATA[
17:13:01.540 [main] TRACE MyApp - Entering application.
17:13:01.540 [main] TRACE com.foo.Bar - entry
17:13:01.540 [main] ERROR com.foo.Bar - Did it again!
17:13:01.540 [main] TRACE com.foo.Bar - exit with (false)
17:13:01.540 [main] ERROR MyApp - Didn't do it.
17:13:01.540 [main] TRACE MyApp - Exiting application.
]]></pre>
          <p>
            Note that status logging is disabled when the default configuration is used.
          </p>
        </subsection>
        <a name="Additivity"/>
        <subsection name="Additivity">
          <p>
            Perhaps it is desired to eliminate all the TRACE output from everything except <code>com.foo.Bar</code>.
            Simply changing the log level would not accomplish the task. Instead, the solution is to
            add a new logger definition to the configuration:
          </p>
            <pre class="prettyprint linenums"><![CDATA[
<Logger name="com.foo.Bar" level="TRACE"/>
<Root level="ERROR">
  <AppenderRef ref="STDOUT">
</Root>
]]></pre>
          <p>
            With this configuration all log events from <code>com.foo.Bar</code> will be recorded while only error
            events will be recorded from all other components.
          </p>
          <p>
            In the previous example all the events from <code>com.foo.Bar</code> were still written to the Console. This is
            because the logger for <code>com.foo.Bar</code> did not have any appenders configured while its parent did. In fact,
            the following configuration
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Logger name="com.foo.Bar" level="trace">
      <AppenderRef ref="Console"/>
    </Logger>
    <Root level="error">
      <AppenderRef ref="Console"/>
    </Root>
  </Loggers>
</Configuration>
]]></pre>
          <p>would result in</p>
          <pre><![CDATA[
17:13:01.540 [main] TRACE com.foo.Bar - entry
17:13:01.540 [main] TRACE com.foo.Bar - entry
17:13:01.540 [main] ERROR com.foo.Bar - Did it again!
17:13:01.540 [main] TRACE com.foo.Bar - exit (false)
17:13:01.540 [main] TRACE com.foo.Bar - exit (false)
17:13:01.540 [main] ERROR MyApp - Didn't do it.
]]></pre>
          <p>Notice that the trace messages from <code>com.foo.Bar</code> appear twice. This is because the appender associated
            with logger <code>com.foo.Bar</code> is first used, which writes the first instance to the Console. Next, the parent
            of <code>com.foo.Bar</code>, which in this case is the root logger, is referenced. The event is then passed to its
            appender, which is also writes to the Console, resulting in the second instance. This is known as
            additivity. While additivity can be quite a convenient feature (as in the first previous example where
            no appender reference needed to be configured), in many cases this behavior is considered undesirable
            and so it is possible to disable it by setting the additivity attribute on the logger to false:
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Logger name="com.foo.Bar" level="trace" additivity="false">
      <AppenderRef ref="Console"/>
    </Logger>
    <Root level="error">
      <AppenderRef ref="Console"/>
    </Root>
  </Loggers>
</Configuration>
]]></pre>
          <p>
            Once an event reaches a logger with its additivity set to false the event will not be passed to
            any of its parent loggers, regardless of their additivity setting.
          </p>
        </subsection>
        <a name="AutomaticReconfiguration"/>
        <subsection name="Automatic Reconfiguration">
          <p>
            When configured from a File, Log4j has the ability to automatically detect changes to the configuration
            file and reconfigure itself. If the <code>monitorInterval</code> attribute is specified on the configuration
            element and is set to a non-zero value then the file will be checked the next time a log event is evaluated
            and/or logged and the monitorInterval has elapsed since the last check. The example below shows how
            to configure the attribute so that the configuration file will be checked for changes only after at
            least 30 seconds have elapsed.  The minimum interval is 5 seconds.
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration monitorInterval="30">
...
</Configuration>
]]></pre>
        </subsection>
        <a name="ChainsawSupport"/>
        <subsection name="Chainsaw can automatically process your log files (Advertising appender configurations)">
          <p>
            Log4j provides the ability to 'advertise' appender configuration details for all file-based appenders as well
            as socket-based appenders.  For example, for file-based appenders, the file location and the pattern layout in the file
            are included in the advertisement.  Chainsaw and other external systems can discover these advertisements and
            use that information to intelligently process the log file.
          </p>
          <p>
            The mechanism by which an advertisement is exposed, as well as the advertisement format, is specific to each
            Advertiser implementation.  An external system which would like to work with a specific Advertiser implementation
            must understand how to locate the advertised configuration as well as the format of the advertisement.  For example,
            a 'database' Advertiser may store configuration details in a database table.  An external system can read
            that database table in order to discover the file location and the file format.
          </p>
          <p>
            Log4j provides one Advertiser implementation, a 'multicastdns' Advertiser, which advertises appender configuration
            details via IP multicast using the <a href="http://jmdns.sourceforge.net">http://jmdns.sourceforge.net</a> library.
          </p>
          <p>
            Chainsaw automatically discovers log4j's multicastdns-generated advertisements and displays those discovered
            advertisements in Chainsaw's Zeroconf tab (if the jmdns library is in Chainsaw's classpath).  To begin parsing and tailing
            a log file provided in an advertisement, just double-click the advertised entry in Chainsaw's Zeroconf tab.
            Currently, Chainsaw only supports FileAppender advertisements.
          </p>
          <p>
            To advertise an appender configuration:
          </p>
            <ul>
              <li>Add the JmDns library from <a href="http://jmdns.sourceforge.net">http://jmdns.sourceforge.net</a> to the application classpath</li>
              <li>Set the 'advertiser' attribute of the configuration element to 'multicastdns'</li>
              <li>Set the 'advertise' attribute on the appender element to 'true'</li>
              <li>If advertising a FileAppender-based configuration, set the 'advertiseURI' attribute on the appender element to an appropriate URI</li>
            </ul>
          <p>
            FileAppender-based configurations require an additional 'advertiseURI' attribute to be specified on the appender.
            The 'advertiseURI' attribute provides Chainsaw with information on how the file can be accessed.
            For example, the file may be remotely accessible to Chainsaw via ssh/sftp by specifying a Commons VFS
            (<a href="http://commons.apache.org/proper/commons-vfs/">http://commons.apache.org/proper/commons-vfs/</a>) sftp:// URI,
            an http:// URI may be used if the file is accessible through a web server, or a file:// URI can be specified
            if accessing the file from a locally-running instance of Chainsaw.
          </p>
          <p>
            Here is an example advertisement-enabled appender configuration which can be used by a locally-running Chainsaw to
            automatically tail the log file (notice the file:// advertiseURI):
          </p>
          <p>
            <b>Please note, you must add the JmDns library from <a href="http://jmdns.sourceforge.net">http://jmdns.sourceforge.net</a>
            to your application classpath in order to advertise with the 'multicastdns' advertiser.</b>
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration advertiser="multicastdns">
...
</Configuration>
<Appenders>
  <File name="File1" fileName="output.log" bufferedIO="false" advertiseURI="file://path/to/output.log" advertise="true">
  ...
  </File>
</Appenders>
]]></pre>
</subsection>
        <a name="ConfigurationSyntax"/>
        <subsection name="Configuration Syntax">
          <p>
            As of version 2.9, for security reasons, Log4j does not process DTD in XML files.
            If you want to split the configuration in multiple files, use <a href="#XInclude">XInclude</a> or
            <a href="#CompositeConfiguration">Composite Configuration</a>.
          </p>
          <p>
            As the previous examples have shown as well as those to follow, Log4j allows you to easily
            redefine logging behavior without needing to modify your application. It is possible to
            disable logging for certain parts of the application, log only when specific criteria are met such
            as the action being performed for a specific user, route output to Flume or a log reporting system,
            etc. Being able to do this requires understanding the syntax of the configuration files.
          </p>
          <p>
            The configuration element in the XML file accepts several attributes:
          </p>
            <table>
              <tr>
                <th>Attribute Name</th>
                <th>Description</th>
              </tr>
              <tr>
                <td>advertiser</td>
                <td>(Optional) The Advertiser plugin name which will be used to advertise individual
                FileAppender or SocketAppender configurations.  The only Advertiser plugin provided is 'multicastdns".</td>
              </tr>
              <tr>
                <td>dest</td>
                <td>Either "err" for stderr, "out" for stdout, a file path, or a URL.</td>
              </tr>

              <tr>
                <td>monitorInterval</td>
                <td>The minimum amount of time, in seconds, that must elapse before the file configuration
                  is checked for changes.</td>
              </tr>
              <tr>
                <td>name</td>
                <td>The name of the configuration.</td>
              </tr>
              <tr>
                <td>packages</td>
                <td>A comma separated list of package names to search for plugins. Plugins are only loaded
                  once per classloader so changing this value may not have any effect upon reconfiguration.</td>
              </tr>
              <tr>
                <td>schema</td>
                <td>Identifies the location for the classloader to located the XML Schema to use to validate
                  the configuration. Only valid when strict is set to true. If not set no schema validation
                  will take place.</td>
              </tr>
              <tr>
                 <td>shutdownHook</td>
                 <td>Specifies whether or not Log4j should automatically shutdown when the JVM shuts down. The
                 shutdown hook is enabled by default but may be disabled by setting this attribute to "disable"</td>
              </tr>
              <tr>
                 <td>shutdownTimeout</td>
                 <td>Specifies how many milliseconds appenders and background tasks will get to shutdown when the JVM shuts
                 down. Default is zero which mean that each appender uses its default timeout, and don't wait for background
                 tasks. Not all appenders will honor this, it is a hint and not an absolute guarantee that the shutdown
                 procedure will not take longer. Setting this too low increase the risk of losing outstanding log events
                 not yet written to the final destination. See <a class="javadoc"
                 href="../log4j-core/target/site/apidocs/org/apache/logging/log4j/core/LoggerContext.html${esc.hash}stop(long, java.util.concurrent.TimeUnit)">LoggerContext.stop(long,
                     java.util.concurrent.TimeUnit)</a>.
                  (Not used if <tt>shutdownHook</tt> is set to "disable".)</td>
              </tr>
              <tr>
                <td>status</td>
                <td><p>The level of internal Log4j events that should be logged to the console.
                Valid values for this attribute are "trace", "debug", "info", "warn", "error" and "fatal".
                Log4j will log details about initialization, rollover and other internal actions to the status logger.
                Setting <tt>status="trace"</tt> is one of the first tools available to you if you need to
                troubleshoot log4j.
                </p><p>
                  (Alternatively, setting system property <tt>log4j2.debug</tt> will also print internal Log4j2 logging
                  to the console, including internal logging that took place before the configuration file was found.)
                </p></td>
              </tr>
              <tr>
                <td>strict</td>
                <td>Enables the use of the strict XML format. Not supported in JSON configurations.</td>
              </tr>
              <tr>
                <td>verbose</td>
                <td>Enables diagnostic information while loading plugins.</td>
              </tr>
            </table>
          <a name="XML"/><h3>Configuration with XML</h3>
          <p>
            Log4j can be configured using two XML flavors; concise and strict. The concise format makes
            configuration very easy as the element names match the components they represent however it
            cannot be validated with an XML schema. For example, the ConsoleAppender is configured by
            declaring an XML element named Console under its parent appenders element. However, element
            and attribute names are are not case sensitive. In addition, attributes can either be specified
            as an XML attribute or as an XML element that has no attributes and has a text value. So
          </p>
          <pre class="prettyprint"><![CDATA[<PatternLayout pattern="%m%n"/>]]></pre>
          <p>and</p>
          <pre class="prettyprint"><![CDATA[
<PatternLayout>
  <Pattern>%m%n</Pattern>
</PatternLayout>]]></pre>
          <p>
            are equivalent.
          </p>
          <p>
            The file below represents the structure of an XML configuration, but note
            that the elements in italics below represent the concise element names that would appear in their place.
          </p>

          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>;
<Configuration>
  <Properties>
    <Property name="name1">value</property>
    <Property name="name2" value="value2"/>
  </Properties>
  <]]><i>filter</i>  ... <![CDATA[/>
  <Appenders>
    <]]><i>appender</i> ... <![CDATA[>
      <]]><i>filter</i>  ... <![CDATA[/>
    </]]><i>appender</i><![CDATA[>
    ...
  </Appenders>
  <Loggers>
    <Logger name="name1">
      <]]><i>filter</i>  ... <![CDATA[/>
    </Logger>
    ...
    <Root level="level">
      <AppenderRef ref="name"/>
    </Root>
  </Loggers>
</Configuration>
]]></pre>
          <p>
            See the many examples on this page for sample appender, filter and logger declarations.
          </p>
            <h5>Strict XML</h5>
          <p>
            In addition to the concise XML format above, Log4j allows configurations to be specified in a
            more "normal" XML manner that can be validated using an XML Schema. This is accomplished by
            replacing the friendly element names above with their object type as shown below. For example,
            instead of the ConsoleAppender being configuerd using an element named Console it is instead
            configured as an appender element with a type attribute containing "Console".
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>;
<Configuration>
  <Properties>
    <Property name="name1">value</property>
    <Property name="name2" value="value2"/>
  </Properties>
  <Filter type="type" ... />
  <Appenders>
    <Appender type="type" name="name">
      <Filter type="type" ... />
    </Appender>
    ...
  </Appenders>
  <Loggers>
    <Logger name="name1">
      <Filter type="type" ... />
    </Logger>
    ...
    <Root level="level">
      <AppenderRef ref="name"/>
    </Root>
  </Loggers>
</Configuration>
]]></pre>
          <p>
            Below is a sample configuration using the strict format.
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="debug" strict="true" name="XMLConfigTest"
               packages="org.apache.logging.log4j.test">
  <Properties>
    <Property name="filename">target/test.log</Property>
  </Properties>
  <Filter type="ThresholdFilter" level="trace"/>

  <Appenders>
    <Appender type="Console" name="STDOUT">
      <Layout type="PatternLayout" pattern="%m MDC%X%n"/>
      <Filters>
        <Filter type="MarkerFilter" marker="FLOW" onMatch="DENY" onMismatch="NEUTRAL"/>
        <Filter type="MarkerFilter" marker="EXCEPTION" onMatch="DENY" onMismatch="ACCEPT"/>
      </Filters>
    </Appender>
    <Appender type="Console" name="FLOW">
      <Layout type="PatternLayout" pattern="%C{1}.%M %m %ex%n"/><!-- class and line number -->
      <Filters>
        <Filter type="MarkerFilter" marker="FLOW" onMatch="ACCEPT" onMismatch="NEUTRAL"/>
        <Filter type="MarkerFilter" marker="EXCEPTION" onMatch="ACCEPT" onMismatch="DENY"/>
      </Filters>
    </Appender>
    <Appender type="File" name="File" fileName="${dollar}{filename}">
      <Layout type="PatternLayout">
        <Pattern>%d %p %C{1.} [%t] %m%n</Pattern>
      </Layout>
    </Appender>
  </Appenders>

  <Loggers>
    <Logger name="org.apache.logging.log4j.test1" level="debug" additivity="false">
      <Filter type="ThreadContextMapFilter">
        <KeyValuePair key="test" value="123"/>
      </Filter>
      <AppenderRef ref="STDOUT"/>
    </Logger>

    <Logger name="org.apache.logging.log4j.test2" level="debug" additivity="false">
      <AppenderRef ref="File"/>
    </Logger>

    <Root level="trace">
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>

</Configuration>
]]></pre>
        <a name="JSON"/>
          <h4>Configuration with JSON</h4>
          <p>
            In addition to XML, Log4j can be configured using JSON. The JSON format is very similar to the
            concise XML format. Each key represents the name of a plugin and the key/value pairs associated
            with it are its attributes. Where a key contains more than a simple value it itself will be a
            subordinate plugin. In the example below, ThresholdFilter, Console, and PatternLayout are all
            plugins while the Console plugin will be assigned a value of STDOUT for its name attribute and the
            ThresholdFilter will be assigned a level of debug.
          </p>
          <pre class="prettyprint linenums"><![CDATA[
{ "configuration": { "status": "error", "name": "RoutingTest",
                     "packages": "org.apache.logging.log4j.test",
      "properties": {
        "property": { "name": "filename",
                      "value" : "target/rolling1/rollingtest-${dollar}${dollar}{sd:type}.log" }
      },
    "ThresholdFilter": { "level": "debug" },
    "appenders": {
      "Console": { "name": "STDOUT",
        "PatternLayout": { "pattern": "%m%n" },
        "ThresholdFilter": { "level": "debug" }
      },
      "Routing": { "name": "Routing",
        "Routes": { "pattern": "${dollar}${dollar}{sd:type}",
          "Route": [
            {
              "RollingFile": {
                "name": "Rolling-${dollar}{sd:type}", "fileName": "${dollar}{filename}",
                "filePattern": "target/rolling1/test1-${dollar}{sd:type}.%i.log.gz",
                "PatternLayout": {"pattern": "%d %p %c{1.} [%t] %m%n"},
                "SizeBasedTriggeringPolicy": { "size": "500" }
              }
            },
            { "AppenderRef": "STDOUT", "key": "Audit"}
          ]
        }
      }
    },
    "loggers": {
      "logger": { "name": "EventLogger", "level": "info", "additivity": "false",
                  "AppenderRef": { "ref": "Routing" }},
      "root": { "level": "error", "AppenderRef": { "ref": "STDOUT" }}
    }
  }
}
]]></pre>
           <p>
            Note that in the RoutingAppender the Route element has been declared as an array. This is
            valid because each array element will be a Route component. This won't work for elements such as
            appenders and filters, where each element has a different name in the concise format. Appenders and
            filters can be defined as array elements if each appender or filter declares an attribute named "type"
            that contains the type of the appender. The following example illustrates this as well as how to
            declare multiple loggers as an array.
          </p>
           <pre class="prettyprint linenums"><![CDATA[
{ "configuration": { "status": "debug", "name": "RoutingTest",
                      "packages": "org.apache.logging.log4j.test",
      "properties": {
        "property": { "name": "filename",
                      "value" : "target/rolling1/rollingtest-${dollar}${dollar}{sd:type}.log" }
      },
    "ThresholdFilter": { "level": "debug" },
    "appenders": {
      "appender": [
         { "type": "Console", "name": "STDOUT", "PatternLayout": { "pattern": "%m%n" }, "ThresholdFilter": { "level": "debug" }},
         { "type": "Routing",  "name": "Routing",
          "Routes": { "pattern": "${dollar}${dollar}{sd:type}",
            "Route": [
              {
                "RollingFile": {
                  "name": "Rolling-${dollar}{sd:type}", "fileName": "${dollar}{filename}",
                  "filePattern": "target/rolling1/test1-${dollar}{sd:type}.%i.log.gz",
                  "PatternLayout": {"pattern": "%d %p %c{1.} [%t] %m%n"},
                  "SizeBasedTriggeringPolicy": { "size": "500" }
                }
              },
              { "AppenderRef": "STDOUT", "key": "Audit"}
            ]
          }
        }
      ]
    },
    "loggers": {
      "logger": [
        { "name": "EventLogger", "level": "info", "additivity": "false",
          "AppenderRef": { "ref": "Routing" }},
        { "name": "com.foo.bar", "level": "error", "additivity": "false",
          "AppenderRef": { "ref": "STDOUT" }}
      ],
      "root": { "level": "error", "AppenderRef": { "ref": "STDOUT" }}
    }
  }
}
]]></pre>
          <p>
            Additional <a href="../runtime-dependencies.html">runtime dependencies</a> are required for using
            JSON configuration files.
          </p>
          <a name="YAML"/>
          <h4>Configuration with YAML</h4>
          <p>
            Log4j also supports using YAML for configuration files. The structure follows the same pattern as both the
            XML and YAML configuration formats. For example:
          </p>
          <pre class="prettyprint linenums"><![CDATA[
Configuration:
  status: warn
  name: YAMLConfigTest
  properties:
    property:
      name: filename
      value: target/test-yaml.log
  thresholdFilter:
    level: debug
  appenders:
    Console:
      name: STDOUT
      PatternLayout:
        Pattern: "%m%n"
    File:
      name: File
      fileName: ${dollar}{filename}
      PatternLayout:
        Pattern: "%d %p %C{1.} [%t] %m%n"
      Filters:
        ThresholdFilter:
          level: error

  Loggers:
    logger:
      -
        name: org.apache.logging.log4j.test1
        level: debug
        additivity: false
        ThreadContextMapFilter:
          KeyValuePair:
            key: test
            value: 123
        AppenderRef:
          ref: STDOUT
      -
        name: org.apache.logging.log4j.test2
        level: debug
        additivity: false
        AppenderRef:
          ref: File
    Root:
      level: error
      AppenderRef:
        ref: STDOUT
          ]]></pre>
          <p>
            Additional <a href="../runtime-dependencies.html">runtime dependencies</a> are required for using
            YAML configuration files.
          </p>
          <a name="Properties"/>
          <h4>Configuration with Properties</h4>
            <p>
              As of version 2.4, Log4j now supports configuration via properties files. Note that the property
              syntax is NOT the same as the syntax used in Log4j 1. Like the XML and JSON configurations, properties
              configurations define the configuration in terms of plugins and attributes to the plugins.
            </p>
            <p>
              Prior to version 2.6,
              the properties configuration requires that you list the identifiers of the appenders, filters and loggers,
              in a comma separated list in properties with those names. Each of those components will then be expected
              to be defined in sets of properties that begin with <i>component.&lt;.identifier&gt;.</i>. The identifier does not
              have to match the name of the component being defined but must uniquely identify all the attributes and
              subcomponents that are part of the component. If the list of identifiers is not present the
              identier must not contain a '.'. Each individual component MUST have a "type" attribute
              specified that identifies the component's Plugin type.
            </p>
            <p>
              As of version 2.6, this list of identifiers is no longer required as names are inferred upon first usage,
              however if you wish to use more complex identifies you must still use the list. If the list is present
              it will be used.
            </p>
            <p>
              Unlike the base components, when creating subcomponents you cannot specify an element containing a list of
              identifiers. Instead, you must define the wrapper element with its type as is shown in the policies
              definition in the rolling file appender below. You then define each of the subcomponents below that
              wrapper element, as the TimeBasedTriggeringPolicy and SizeBasedTriggeringPolicy are defined below.
            </p>
            <p>
              Properties configuration files support the advertiser, monitorInterval, name, packages, shutdownHook,
              shutdownTimeout, status, verbose, and dest attrbutes. See <a href="#ConfigurationSyntax">Configuration Syntax</a>
              for the definitions of these attributes.
            </p>
          <pre class="prettyprint linenums">
status = error
dest = err
name = PropertiesConfig

property.filename = target/rolling/rollingtest.log

filter.threshold.type = ThresholdFilter
filter.threshold.level = debug

appender.console.type = Console
appender.console.name = STDOUT
appender.console.layout.type = PatternLayout
appender.console.layout.pattern = %m%n
appender.console.filter.threshold.type = ThresholdFilter
appender.console.filter.threshold.level = error

appender.rolling.type = RollingFile
appender.rolling.name = RollingFile
appender.rolling.fileName = ${filename}
appender.rolling.filePattern = target/rolling2/test1-%d{MM-dd-yy-HH-mm-ss}-%i.log.gz
appender.rolling.layout.type = PatternLayout
appender.rolling.layout.pattern = %d %p %C{1.} [%t] %m%n
appender.rolling.policies.type = Policies
appender.rolling.policies.time.type = TimeBasedTriggeringPolicy
appender.rolling.policies.time.interval = 2
appender.rolling.policies.time.modulate = true
appender.rolling.policies.size.type = SizeBasedTriggeringPolicy
appender.rolling.policies.size.size=100MB
appender.rolling.strategy.type = DefaultRolloverStrategy
appender.rolling.strategy.max = 5

logger.rolling.name = com.example.my.app
logger.rolling.level = debug
logger.rolling.additivity = false
logger.rolling.appenderRef.rolling.ref = RollingFile

rootLogger.level = info
rootLogger.appenderRef.stdout.ref = STDOUT
          </pre>
          <a name="Loggers"/>
          <h4>Configuring loggers</h4>
          <p>
            An understanding of how loggers work in Log4j is critical before trying to configure them.
            Please reference the Log4j <a href="./architecture.html">architecture</a> if more information is
            required. Trying to configure Log4j without understanding those concepts will lead to frustration.
          </p>
          <p>
            A LoggerConfig is configured using the <code>logger</code> element. The <code>logger</code> element
            must have a name attribute specified, will usually have a level attribute specified and may
            also have an additivity attribute specified.  The level may be configured with one of TRACE,
            DEBUG, INFO, WARN, ERROR, ALL or OFF. If no level is specified it will default to ERROR. The
            additivity attribute may be assigned a value of true or false. If the attribute is omitted
            the default value of true will be used.
          </p>
          <p>
            A LoggerConfig (including the root LoggerConfig) can be configured with properties that will be added
            to the properties copied from the ThreadContextMap. These properties can be referenced from Appenders,
            Filters, Layouts, etc just as if they were part of the ThreadContext Map. The properties can contain
            variables that will be resolved either when the configuration is parsed or dynamically when each
            event is logged. See <a href="#PropertySubstitution">Property Substitution</a> for more information on
            using variables.
          </p>
          <p>
            The LoggerConfig may also be configured with one or more AppenderRef elements. Each appender
            referenced will become associated with the specified LoggerConfig. If multiple appenders
            are configured on the LoggerConfig each of them be called when processing logging events.
          </p>
          <p>
            <b><em>Every configuration must have a root logger</em></b>. If one is not configured the default root LoggerConfig,
            which has a level of ERROR and has a Console appender attached, will be used. The main differences
            between the root logger and other loggers are
          </p>
          <ol>
            <li>The root logger does not have a name attribute.</li>
            <li>The root logger does not support the additivity attribute since it has no parent.</li>
          </ol>
          <a name="Appenders"/>
          <h4>Configuring Appenders</h4>
          <p>
            An appender is configured either using the specific appender plugin's name or with an appender
            element and the type attibute containing the appender plugin's name. In addition each appender
            must have a name attribute specified with a value that is unique within the set of appenders.
            The name will be used by loggers to reference the appender as described in the previous section.
          </p>
          <p>
            Most appenders also support a layout to be configured (which again may be specified either
            using the specific Layout plugin's name as the element or with "layout" as the element name
            along with a type attribute that contains the layout plugin's name. The various appenders
            will contain other attributes or elements that are required for them to function properly.
          </p>
          <a name="Filters"/>
          <h4>Configuring Filters</h4>
          <p>
            Log4j allows a filter to be specified in any of 4 places:
          </p>
          <ol>
            <li>At the same level as the appenders, loggers and properties elements. These filters can accept
              or reject events before they have been passed to a LoggerConfig.</li>
            <li>In a logger element. These filters can accept or reject events for specific loggers.</li>
            <li>In an appender element. These filters can prevent or cause events to be processed by
              the appender.</li>
            <li>In an appender reference element. These filters are used to determine if a Logger should route
              the event to an appender.</li>
          </ol>
          <p>
            Although only a single <code>filter</code> element can be configured, that element may be the
            <code>filters</code> element which represents the CompositeFilter. The <code>filters</code> element
            allows any number of <code>filter</code> elements to be configured within it. The following example
            shows how multiple filters can be configured on the ConsoleAppender.
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="debug" name="XMLConfigTest" packages="org.apache.logging.log4j.test">
  <Properties>
    <Property name="filename">target/test.log</Property>
  </Properties>
  <ThresholdFilter level="trace"/>

  <Appenders>
    <Console name="STDOUT">
      <PatternLayout pattern="%m MDC%X%n"/>
    </Console>
    <Console name="FLOW">
      <!-- this pattern outputs class name and line number -->
      <PatternLayout pattern="%C{1}.%M %m %ex%n"/>
      <filters>
        <MarkerFilter marker="FLOW" onMatch="ACCEPT" onMismatch="NEUTRAL"/>
        <MarkerFilter marker="EXCEPTION" onMatch="ACCEPT" onMismatch="DENY"/>
      </filters>
    </Console>
    <File name="File" fileName="${dollar}{filename}">
      <PatternLayout>
        <pattern>%d %p %C{1.} [%t] %m%n</pattern>
      </PatternLayout>
    </File>
  </Appenders>

  <Loggers>
    <Logger name="org.apache.logging.log4j.test1" level="debug" additivity="false">
      <ThreadContextMapFilter>
        <KeyValuePair key="test" value="123"/>
      </ThreadContextMapFilter>
      <AppenderRef ref="STDOUT"/>
    </Logger>

    <Logger name="org.apache.logging.log4j.test2" level="debug" additivity="false">
      <Property name="user">${dollar}{sys:user.name}</Property>
      <AppenderRef ref="File">
        <ThreadContextMapFilter>
          <KeyValuePair key="test" value="123"/>
        </ThreadContextMapFilter>
      </AppenderRef>
      <AppenderRef ref="STDOUT" level="error"/>
    </Logger>

    <Root level="trace">
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>

</Configuration>
]]></pre>
        </subsection>
        <a name="PropertySubstitution"/>
        <subsection name="Property Substitution">
          <p>
            Log4j 2 supports the ability to specify tokens in the configuration as references to properties defined
            elsewhere. Some of these properties will be resolved when the configuration file is interpreted while
            others may be passed to components where they will be evaluated at runtime. To accomplish this, Log4j
            uses variations of <a href="https://commons.apache.org/proper/commons-lang/">Apache Commons Lang</a>'s
            <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/lookup/StrSubstitutor.html">StrSubstitutor</a>
            and <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/lookup/StrLookup.html">StrLookup</a>
            classes. In a manner similar to Ant or Maven, this allows variables declared as <code>${dollar}{name}</code>
            to be resolved using properties declared in the configuration itself. For example, the following example
            shows the filename for the rolling file appender being declared as a property.
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="debug" name="RoutingTest" packages="org.apache.logging.log4j.test">
  <Properties>
    <Property name="filename">target/rolling1/rollingtest-${dollar}${dollar}{sd:type}.log</Property>
  </Properties>
  <ThresholdFilter level="debug"/>

  <Appenders>
    <Console name="STDOUT">
      <PatternLayout pattern="%m%n"/>
      <ThresholdFilter level="debug"/>
    </Console>
    <Routing name="Routing">
      <Routes pattern="${dollar}${dollar}{sd:type}">
        <Route>
          <RollingFile name="Rolling-${dollar}{sd:type}" fileName="${dollar}{filename}"
                       filePattern="target/rolling1/test1-${dollar}{sd:type}.%i.log.gz">
            <PatternLayout>
              <pattern>%d %p %c{1.} [%t] %m%n</pattern>
            </PatternLayout>
            <SizeBasedTriggeringPolicy size="500" />
          </RollingFile>
        </Route>
        <Route ref="STDOUT" key="Audit"/>
      </Routes>
    </Routing>
  </Appenders>

  <Loggers>
    <Logger name="EventLogger" level="info" additivity="false">
      <AppenderRef ref="Routing"/>
    </Logger>

    <Root level="error">
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>

</Configuration>
]]></pre>
          <p>
            While this is useful, there are many more places properties can originate from. To accommodate this,
            Log4j also supports the syntax <code>${dollar}{prefix:name}</code> where the prefix identifies tells Log4j
            that variable name should be evaluated in a specific context.
            See the <a href="lookups.html">Lookups</a> manual page for more details.
            The contexts that are built in to Logj4 are:
          </p>
            <table>
              <tr>
                <th>Prefix</th>
                <th>Context</th>
              </tr>
              <tr>
                <td>base64</td>
                <td>
                  Base64 encoded data. The format is <code>${dollar}{base64:Base64_encoded_data}</code>.
                  For example:
                  <code>${dollar}{base64:SGVsbG8gV29ybGQhCg==}</code> yields <code>Hello World!</code>.
                </td>
              </tr>
              <tr>
                <td>bundle</td>
                <td>
                  Resource bundle. The format is <code>${dollar}{bundle:BundleName:BundleKey}</code>.
                  The bundle name follows package naming conventions, for example:
                  <code>${dollar}{bundle:com.domain.Messages:MyKey}</code>.
                </td>
              </tr>
              <tr>
                <td>ctx</td>
                <td>Thread Context Map (MDC)</td>
              </tr>
              <tr>
                <td>date</td>
                <td>Inserts the current date and/or time using the specified format</td>
              </tr>
              <tr>
                <td>env</td>
                <td>System environment variables. The formats are <code>${dollar}{env:ENV_NAME}</code> and <code>${dollar}{env:ENV_NAME:-default_value}</code>.</td>
              </tr>
              <tr>
                <td>jndi</td>
                <td>A value set in the default JNDI Context.</td>
              </tr>
              <tr>
                <td>jvmrunargs</td>
                <td>
                  A JVM input argument accessed through JMX, but not a main argument;
                  see <a class="javadoc" href="http://docs.oracle.com/javase/6/docs/api/java/lang/management/RuntimeMXBean.html#getInputArguments--">RuntimeMXBean.getInputArguments()</a>.
                  Not available on Android.</td>
              </tr>
              <tr>
                <td>log4j</td>
                <td>Log4j configuration properties. The expressions <code>${dollar}{log4j:configLocation}</code> and
                  <code>${dollar}{log4j:configParentLocation}</code> respectively provide the absolute path
                  to the log4j configuration file and its parent folder.</td>
              </tr>
              <tr>
                <td>main</td>
                <td>A value set with <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/lookup/MapLookup.html#setMainArguments-java.lang.String:A-">MapLookup.setMainArguments(String[])</a></td>
              </tr>
              <tr>
                <td>map</td>
                <td>A value from a MapMessage</td>
              </tr>
              <tr>
                <td>sd</td>
                <td>A value from a StructuredDataMessage. The key "id" will return the name of the StructuredDataId
                  without the enterprise number. The key "type" will return the message type. Other keys will
                  retrieve individual elements from the Map.</td>
              </tr>
              <tr>
                <td>sys</td>
                <td>System properties. The formats are <code>${dollar}{sys:some.property}</code> and <code>${dollar}{sys:some.property:-default_value}</code>.</td>
              </tr>
            </table>
          <a name="DefaultProperties"/><h3>Default Properites</h3><p>
          A default property map can be declared in the configuration file by placing a Properties
          element directly after the Configuration element and before any Loggers, Filters,
          Appenders, etc. are declared. If the value cannot be located in the specified lookup the
          value in the default property map will be used. The default map is pre-populated with a value
          for "hostName" that is the current system's host name or IP address and
          the "contextName" with is the value of the current logging context. See many places
          a Properties element is used in this section for examples.
          </p>
        </subsection>
        <a name="RuntimeLookup"/>
        <subsection name="Lookup Variables with Multiple Leading '$' Characters">
          <p>
            An interesting feature of StrLookup processing is that when a variable reference is declared with
            multiple leading '$' characters each time the variable is resolved the leading '$' is simply removed.
            In the previous example the "Routes" element is capable of resolving the variable at runtime. To allow
            this the prefix value is specified as a variable with two leading '$' characters. When the configuration
            file is first processed the first '$' character is simply removed. Thus, when the Routes element is evaluated
            at runtime it is the variable declaration "${dollar}{sd:type}" which causes the event to be inspected for a
            StructuredDataMessage and if one is present the value of its type attribute to be used as the routing key.
            Not all elements support resolving variables at runtime. Components that do will specifically call that
            out in their documentation.
          </p>
          <p>
            If no value is found for the key in the Lookup associated with the prefix then the value associated with
            the key in the properties declaration in the configuration file will be used. If no value is found
            the variable declaration will be returned as the value. Default values may be declared in the configuration
            by doing:
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
  <Properties>
    <Property name="type">Audit</property>
  </Properties>
  ...
</Configuration>
]]></pre>
          <p>
            <i>As a footnote, it is worth pointing out that the variables in the RollingFile appender declaration
            will also not be evaluated when the configuration is processed. This is simply because the resolution
            of the whole RollingFile element is deferred until a match occurs.
            See <a href="appenders.html#RoutingAppender">RoutingAppender</a> for more information.</i>
          </p>
        </subsection>
        <a name="Scripts"/>
        <subsection name="Scripts">
          <p>
            Log4j provides support for <a href="http://docs.oracle.com/javase/6/docs/technotes/guides/scripting/">JSR 223</a>
            scripting languages to be used in some of its components. Any language that provides support for the JSR
            223 scripting engine may be used. A list of the languages and bindings for them can be found at the
            <a href="https://java.net/projects/scripting/sources/svn/show/trunk/engines">Scripting Engine</a> web site.
            However, some of the languages listed there, such as JavaScript, Groovy and Beanshell, directly support the
            JSR 223 scripting framework and only require that the jars for that language be installed.
          </p>
          <p>
            The components that support using scripts do so by allowing a &lt;script&gt;, &lt;scriptFile&gt;, or
            &lt;scriptRef&gt; element to be configured on
            them. The script element contains a name for the script, the language of the script, and the script text.
            The scriptFile element contains the name of the script, its location, its language, its charset, and
            whether the file should be watched for changes. The scriptRef element contains the name of the
            script that is defined in the &lt;scripts&gt; configuration element.
            The name of the script is used to store the script, along with its ScriptEngine, so it can quickly be
            located each time the script needs to be run. While the name is not required, providing it will help in
            debugging problems when the script is running. The language must be provided on the script element and must
            specify one of the language names that appear in the Configuration status log as described in the next
            section. If the language is not specified on the scriptFile element the language will be determined by
            the file extension of the script path. If file monitoring is requested it will only be enabled if
            a non-zero monitorInterval is specified on the configuration element. That interval will be used to
            check for changes in the file.
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="debug" name="RoutingTest">
  <Scripts>
    <Script name="selector" language="javascript"><![CDATA[
            var result;
            if (logEvent.getLoggerName().equals("JavascriptNoLocation")) {
                result = "NoLocation";
            } else if (logEvent.getMarker() != null && logEvent.getMarker().isInstanceOf("FLOW")) {
                result = "Flow";
            }
            result;
            ]]]]><![CDATA[></Script>
    <ScriptFile name="groovy.filter" path="scripts/filter.groovy"/>
  </Scripts>

  <Appenders>
    <Console name="STDOUT">
      <ScriptPatternSelector defaultPattern="%d %p %m%n">
        <ScriptRef ref="selector"/>
          <PatternMatch key="NoLocation" pattern="[%-5level] %c{1.} %msg%n"/>
          <PatternMatch key="Flow" pattern="[%-5level] %c{1.} ====== %C{1.}.%M:%L %msg ======%n"/>
      </ScriptPatternSelector>
      <PatternLayout pattern="%m%n"/>
    </Console>
  </Appenders>

  <Loggers>
    <Logger name="EventLogger" level="info" additivity="false">
        <ScriptFilter onMatch="ACCEPT" onMisMatch="DENY">
          <Script name="GroovyFilter" language="groovy"><![CDATA[
            if (logEvent.getMarker() != null && logEvent.getMarker().isInstanceOf("FLOW")) {
                return true;
            } else if (logEvent.getContextMap().containsKey("UserId")) {
                return true;
            }
            return false;
            ]]]]><![CDATA[>
          </Script>
        </ScriptFilter>
      <AppenderRef ref="STDOUT"/>
    </Logger>

    <Root level="error">
      <ScriptFilter onMatch="ACCEPT" onMisMatch="DENY">
        <ScriptRef ref="groovy.filter"/>
      </ScriptFilter>
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>

</Configuration>]]>
          </pre>
          <p>
            If the status attribute on the Configuration element is set to DEBUG the list of script engines currently
            installed and their attributes will be listed. Although some engines may say they are not thread safe,
            Log4j takes steps to insure that the scripts will run in a thread-safe manner if the engine advertises
            that it is not thread safe.
          </p>
          <pre>
2015-09-27 16:13:22,925 main DEBUG Installed script engines
2015-09-27 16:13:22,963 main DEBUG AppleScriptEngine Version: 1.1, Language: AppleScript, Threading: Not Thread Safe,
            Compile: false, Names: {AppleScriptEngine, AppleScript, OSA}
2015-09-27 16:13:22,983 main DEBUG Groovy Scripting Engine Version: 2.0, Language: Groovy, Threading: MULTITHREADED,
            Compile: true, Names: {groovy, Groovy}
2015-09-27 16:13:23,030 main DEBUG BeanShell Engine Version: 1.0, Language: BeanShell, Threading: MULTITHREADED,
            Compile: true, Names: {beanshell, bsh, java}
2015-09-27 16:13:23,039 main DEBUG Mozilla Rhino Version: 1.7 release 3 PRERELEASE, Language: ECMAScript, Threading: MULTITHREADED,
            Compile: true, Names: {js, rhino, JavaScript, javascript, ECMAScript, ecmascript}
          </pre>
          <p>
            When the scripts are executed they will be provided with a set of variables that should allow them to
            accomplish whatever task they are expected to perform. See the documentation for the individual components
            for the list of variables that are available to the script.
          </p>
          <p>
            The components that support scripting expect a return value to be passed back to the calling Java code.
            This is not a problem for several of the scripting languages, but Javascript does not allow a
            return statement unless it is within a function. However, Javascript will return the value of the last
            statement executed in the script. As a consequence, code such as that shown below will result in the
            desired behavior.
          </p>
          <pre><![CDATA[
            var result;
            if (logEvent.getLoggerName().equals("JavascriptNoLocation")) {
                result = "NoLocation";
            } else if (logEvent.getMarker() != null && logEvent.getMarker().isInstanceOf("FLOW")) {
                result = "Flow";
            }
            result;
          ]]></pre>
          <h4>A special note on Beanshell</h4>
          <p>
            JSR 223 scripting engines are supposed to identify that they support the Compilable interface if they
            support compiling their scripts. Beanshell does this. However, whenever the compile method is called it
            throws an Error (not an Exception). Log4j catches this but will log the warning shown below for each
            Beanshell script when it tries to compile them. All Beanshell scripts will then be interpreted on each
            execution.
          </p>
          <pre><![CDATA[
2015-09-27 16:13:23,095 main DEBUG Script BeanShellSelector is compilable
2015-09-27 16:13:23,096 main WARN Error compiling script java.lang.Error: unimplemented
            at bsh.engine.BshScriptEngine.compile(BshScriptEngine.java:175)
            at bsh.engine.BshScriptEngine.compile(BshScriptEngine.java:154)
            at org.apache.logging.log4j.core.script.ScriptManager$MainScriptRunner.<init>(ScriptManager.java:125)
            at org.apache.logging.log4j.core.script.ScriptManager.addScript(ScriptManager.java:94)
          ]]></pre>
        </subsection>
        <a name="XInclude"/>
        <subsection name="XInclude">
          <p>
            XML configuration files can include other files with <a href="http://www.xml.com/lpt/a/1009">XInclude</a>.
            Here is an example log4j2.xml file that includes two other files:
          </p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<configuration xmlns:xi="http://www.w3.org/2001/XInclude"
               status="warn" name="XIncludeDemo">
  <properties>
    <property name="filename">xinclude-demo.log</property>
  </properties>
  <ThresholdFilter level="debug"/>
  <xi:include href="log4j-xinclude-appenders.xml" />
  <xi:include href="log4j-xinclude-loggers.xml" />
</configuration>
]]></pre>
          <p>log4j-xinclude-appenders.xml:</p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<appenders>
  <Console name="STDOUT">
    <PatternLayout pattern="%m%n" />
  </Console>
  <File name="File" fileName="${dollar}{filename}" bufferedIO="true" immediateFlush="true">
    <PatternLayout>
      <pattern>%d %p %C{1.} [%t] %m%n</pattern>
    </PatternLayout>
  </File>
</appenders>
]]></pre>
          <p>log4j-xinclude-loggers.xml:</p>
          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<loggers>
  <logger name="org.apache.logging.log4j.test1" level="debug" additivity="false">
    <ThreadContextMapFilter>
      <KeyValuePair key="test" value="123" />
    </ThreadContextMapFilter>
    <AppenderRef ref="STDOUT" />
  </logger>

  <logger name="org.apache.logging.log4j.test2" level="debug" additivity="false">
    <AppenderRef ref="File" />
  </logger>

  <root level="error">
    <AppenderRef ref="STDOUT" />
  </root>
</loggers>
]]></pre>
        </subsection>
        <a name="CompositeConfiguration"/>
        <subsection name="Composite Configuration">
            <p>
              Log4j allows multiple configuration files to be used by specifying them as a list of comma separated
              file paths on log4j.configurationFile.  The merge logic can be controlled by specifying a class
                that implements the MergeStrategy interface on the log4j.mergeStrategy property. The default
                merge strategy will merge the files using the following rules:
              <ol>
                <li>The global configuration attributes are aggregated with those in later configurations replacing
                  those in previous configurations, with the exception that the highest status level and the lowest
                  monitorInterval greater than 0 will be used.</li>
                <li>Properties from all configurations are aggregated. Duplicate properties replace those in previous
                  configurations.</li>
                <li>Filters are aggregated under a CompositeFilter if more than one Filter is defined. Since Filters
                  are not named duplicates may be present.</li>
                <li>Scripts and ScriptFile references are aggregated. Duplicate definiations replace those in previous
                  configurations.</li>
                <li>Appenders are aggregated. Appenders with the same name are replaced by those in later
                  configurations, including all of the Appender's subcomponents.</li>
                <li>Loggers are all aggregated. Logger attributes are individually merged with duplicates being
                  replaced by those in later configurations. Appender references on a Logger are aggregated with
                  duplicates being replaced by those in later configurations. Filters on a Logger are aggregated
                  under a CompositeFilter if more than one Filter is defined. Since Filters are not named
                  duplicates may be present. Filters under Appender references included or discarded depending on
                  whether their parent Appender reference is kept or discarded.</li>
                </ol>
            </p>
        </subsection>
        <a name="StatusMessages"/>
        <subsection name="Status Messages">
          <table>
            <tr>
            <td>
            <b>Troubleshooting tip for the impatient:</b>
              <p>From log4j-2.9 onward, log4j2 will print all internal logging to the console if system property
                <tt>log4j2.debug</tt> is defined (with any or no value).</p>
              <p>Prior to log4j-2.9, there are two places where internal logging can be controlled:</p>
            <ul>
              <li>Before a configuration is found, status logger level can be controlled with system
              property <code>org.apache.logging.log4j.simplelog.StatusLogger.level</code>.</li>
              <li>After a configuration is found, status logger level can be controlled in the configuration
              file with the "status" attribute, for example: <code>&lt;Configuration status="trace"&gt;</code>.</li>
            </ul>
            </td>
            </tr>
          </table>
          <p>
            Just as it is desirable to be able to diagnose problems in applications, it is frequently necessary
            to be able to diagnose problems in the logging configuration or in the configured components. Since
            logging has not been configured, "normal" logging cannot be used during initialization. In addition,
            normal logging within appenders could create infinite recursion which Log4j will detect and cause
            the recursive events to be ignored. To accomodate this need, the Log4j 2 API includes a
            <a class="javadoc" href="../log4j-api/apidocs/org/apache/logging/log4j/status/StatusLogger.html">StatusLogger</a>.
            Components declare an instance of the StatusLogger similar to:
          </p>
          <pre class="prettyprint">protected final static Logger logger = StatusLogger.getLogger();</pre>
          <p>
            Since StatusLogger implements the Log4j 2 API's Logger interface, all the normal Logger methods may
            be used.
          </p>
          <p>
            When configuring Log4j it is sometimes necessary to view the generated status events. This can be
            accomplished by adding the status attribute to the configuration element or a default value can be
            provided by setting the "Log4jDefaultStatusLevel" system property.  Valid values of the status attribute are
            "trace", "debug", "info", "warn", "error" and "fatal". The following
            configuration has the status attribute set to debug.
          </p>

          <pre class="prettyprint linenums"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="debug" name="RoutingTest">
  <Properties>
    <Property name="filename">target/rolling1/rollingtest-${dollar}${dollar}{sd:type}.log</Property>
  </Properties>
  <ThresholdFilter level="debug"/>

  <Appenders>
    <Console name="STDOUT">
      <PatternLayout pattern="%m%n"/>
      <ThresholdFilter level="debug"/>
    </Console>
    <Routing name="Routing">
      <Routes pattern="${dollar}${dollar}{sd:type}">
        <Route>
          <RollingFile name="Rolling-${dollar}{sd:type}" fileName="${dollar}{filename}"
                       filePattern="target/rolling1/test1-${dollar}{sd:type}.%i.log.gz">
            <PatternLayout>
              <pattern>%d %p %c{1.} [%t] %m%n</pattern>
            </PatternLayout>
            <SizeBasedTriggeringPolicy size="500" />
          </RollingFile>
        </Route>
        <Route ref="STDOUT" key="Audit"/>
      </Routes>
    </Routing>
  </Appenders>

  <Loggers>
    <Logger name="EventLogger" level="info" additivity="false">
      <AppenderRef ref="Routing"/>
    </Logger>

    <Root level="error">
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>

</Configuration>
]]></pre>
            <p>
            During startup this configuration produces:
            </p>
#if ($isPDF)
    <pre>
2011-11-23 17:08:00,769 DEBUG Generated plugins in 0.003374000 seconds
2011-11-23 17:08:00,789 DEBUG Calling createProperty on class org.apache.logging.log4j.core.
       config.Property for element property with params(name="filename",
       value="target/rolling1/rollingtest-${dollar}{sd:type}.log")
2011-11-23 17:08:00,792 DEBUG Calling configureSubstitutor on class org.apache.logging.log4j.
       core.config.plugins.PropertiesPlugin for element properties with
       params(properties={filename=target/rolling1/rollingtest-${dollar}{sd:type}.log})
2011-11-23 17:08:00,794 DEBUG Generated plugins in 0.001362000 seconds
2011-11-23 17:08:00,797 DEBUG Calling createFilter on class org.apache.logging.log4j.core.
       filter.ThresholdFilter for element ThresholdFilter with params(level="debug",
       onMatch="null", onMismatch="null")
2011-11-23 17:08:00,800 DEBUG Calling createLayout on class org.apache.logging.log4j.core.
       layout.PatternLayout for element PatternLayout with params(pattern="%m%n",
       Configuration(RoutingTest), null, charset="null")
2011-11-23 17:08:00,802 DEBUG Generated plugins in 0.001349000 seconds
2011-11-23 17:08:00,804 DEBUG Calling createAppender on class org.apache.logging.log4j.core.
       appender.ConsoleAppender for element Console with params(PatternLayout(%m%n), null,
       target="null", name="STDOUT", ignoreExceptions="null")
2011-11-23 17:08:00,804 DEBUG Calling createFilter on class org.apache.logging.log4j.core.
       filter.ThresholdFilter for element ThresholdFilter with params(level="debug",
       onMatch="null", onMismatch="null")
2011-11-23 17:08:00,813 DEBUG Calling createRoute on class org.apache.logging.log4j.core.appender.
       routing.Route for element Route with params(AppenderRef="null", key="null", Node=Route)
2011-11-23 17:08:00,823 DEBUG Calling createRoute on class org.apache.logging.log4j.core.appender.
       routing.Route for element Route with params(AppenderRef="STDOUT", key="Audit", Node=Route)
2011-11-23 17:08:00,825 DEBUG Calling createRoutes on class org.apache.logging.log4j.core.appender.
       routing.Routes for element Routes with params(pattern="${dollar}{sd:type}",
       routes={Route(type=dynamic default), Route(type=static Reference=STDOUT key='Audit'))})
2011-11-23 17:08:00,827 DEBUG Calling createAppender on class org.apache.logging.log4j.core.appender.
       routing.RoutingAppender for element Routing with params(name="Routing",
      ignoreExceptions="null", Routes({Route(type=dynamic default),Route(type=static
       Reference=STDOUT key='Audit')}), Configuration(RoutingTest), null, null)
2011-11-23 17:08:00,827 DEBUG Calling createAppenders on class org.apache.logging.log4j.core.config.
       plugins.AppendersPlugin for element appenders with params(appenders={STDOUT, Routing})
2011-11-23 17:08:00,828 DEBUG Calling createAppenderRef on class org.apache.logging.log4j.core.
       config.plugins.AppenderRefPlugin for element AppenderRef with params(ref="Routing")
2011-11-23 17:08:00,829 DEBUG Calling createLogger on class org.apache.logging.log4j.core.config.
       LoggerConfig for element logger with params(additivity="false", level="info", name="EventLogger",
       AppenderRef={Routing}, null)
2011-11-23 17:08:00,830 DEBUG Calling createAppenderRef on class org.apache.logging.log4j.core.
       config.plugins.AppenderRefPlugin for element AppenderRef with params(ref="STDOUT")</pre>
            <pre>
2011-11-23 17:08:00,831 DEBUG Calling createLogger on class org.apache.logging.log4j.core.config.
       LoggerConfig${dollar}RootLogger for element root with params(additivity="null", level="error",
       AppenderRef={STDOUT}, null)
2011-11-23 17:08:00,833 DEBUG Calling createLoggers on class org.apache.logging.log4j.core.
       config.plugins.LoggersPlugin for element loggers with params(loggers={EventLogger, root})
2011-11-23 17:08:00,834 DEBUG Reconfiguration completed
2011-11-23 17:08:00,846 DEBUG Calling createLayout on class org.apache.logging.log4j.core.
       layout.PatternLayout for element PatternLayout with params(pattern="%d %p %c{1.} [%t] %m%n",
       Configuration(RoutingTest), null, charset="null")
2011-11-23 17:08:00,849 DEBUG Calling createPolicy on class org.apache.logging.log4j.core.
       appender.rolling.SizeBasedTriggeringPolicy for element SizeBasedTriggeringPolicy with
       params(size="500")
2011-11-23 17:08:00,851 DEBUG Calling createAppender on class org.apache.logging.log4j.core.
       appender.RollingFileAppender for element RollingFile with
       params(fileName="target/rolling1/rollingtest-Unknown.log",
       filePattern="target/rolling1/test1-Unknown.%i.log.gz", append="null", name="Rolling-Unknown",
       bufferedIO="null", immediateFlush="null",
       SizeBasedTriggeringPolicy(SizeBasedTriggeringPolicy(size=500)), null,
       PatternLayout(%d %p %c{1.} [%t] %m%n), null, ignoreExceptions="null")
2011-11-23 17:08:00,858 DEBUG Generated plugins in 0.002014000 seconds
2011-11-23 17:08:00,889 DEBUG Reconfiguration started for context sun.misc.
       Launcher${dollar}AppClassLoader@37b90b39
2011-11-23 17:08:00,890 DEBUG Generated plugins in 0.001355000 seconds
2011-11-23 17:08:00,959 DEBUG Generated plugins in 0.001239000 seconds
2011-11-23 17:08:00,961 DEBUG Generated plugins in 0.001197000 seconds
2011-11-23 17:08:00,965 WARN No Loggers were configured, using default
2011-11-23 17:08:00,976 DEBUG Reconfiguration completed</pre>
#else
<pre>
2011-11-23 17:08:00,769 DEBUG Generated plugins in 0.003374000 seconds
2011-11-23 17:08:00,789 DEBUG Calling createProperty on class org.apache.logging.log4j.core.config.Property for element property with params(name="filename", value="target/rolling1/rollingtest-${dollar}{sd:type}.log")
2011-11-23 17:08:00,792 DEBUG Calling configureSubstitutor on class org.apache.logging.log4j.core.config.PropertiesPlugin for element properties with params(properties={filename=target/rolling1/rollingtest-${dollar}{sd:type}.log})
2011-11-23 17:08:00,794 DEBUG Generated plugins in 0.001362000 seconds
2011-11-23 17:08:00,797 DEBUG Calling createFilter on class org.apache.logging.log4j.core.filter.ThresholdFilter for element ThresholdFilter with params(level="debug", onMatch="null", onMismatch="null")
2011-11-23 17:08:00,800 DEBUG Calling createLayout on class org.apache.logging.log4j.core.layout.PatternLayout for element PatternLayout with params(pattern="%m%n", Configuration(RoutingTest), null, charset="null")
2011-11-23 17:08:00,802 DEBUG Generated plugins in 0.001349000 seconds
2011-11-23 17:08:00,804 DEBUG Calling createAppender on class org.apache.logging.log4j.core.appender.ConsoleAppender for element Console with params(PatternLayout(%m%n), null, target="null", name="STDOUT", ignoreExceptions="null")
2011-11-23 17:08:00,804 DEBUG Calling createFilter on class org.apache.logging.log4j.core.filter.ThresholdFilter for element ThresholdFilter with params(level="debug", onMatch="null", onMismatch="null")
2011-11-23 17:08:00,813 DEBUG Calling createRoute on class org.apache.logging.log4j.core.appender.routing.Route for element Route with params(AppenderRef="null", key="null", Node=Route)
2011-11-23 17:08:00,823 DEBUG Calling createRoute on class org.apache.logging.log4j.core.appender.routing.Route for element Route with params(AppenderRef="STDOUT", key="Audit", Node=Route)
2011-11-23 17:08:00,825 DEBUG Calling createRoutes on class org.apache.logging.log4j.core.appender.routing.Routes for element Routes with params(pattern="${dollar}{sd:type}", routes={Route(type=dynamic default), Route(type=static Reference=STDOUT key='Audit')})
2011-11-23 17:08:00,827 DEBUG Calling createAppender on class org.apache.logging.log4j.core.appender.routing.RoutingAppender for element Routing with params(name="Routing", ignoreExceptions="null", Routes({Route(type=dynamic default),Route(type=static Reference=STDOUT key='Audit')}), Configuration(RoutingTest), null, null)
2011-11-23 17:08:00,827 DEBUG Calling createAppenders on class org.apache.logging.log4j.core.config.AppendersPlugin for element appenders with params(appenders={STDOUT, Routing})
2011-11-23 17:08:00,828 DEBUG Calling createAppenderRef on class org.apache.logging.log4j.core.config.plugins.AppenderRefPlugin for element AppenderRef with params(ref="Routing")
2011-11-23 17:08:00,829 DEBUG Calling createLogger on class org.apache.logging.log4j.core.config.LoggerConfig for element logger with params(additivity="false", level="info", name="EventLogger", AppenderRef={Routing}, null)
2011-11-23 17:08:00,830 DEBUG Calling createAppenderRef on class org.apache.logging.log4j.core.config.plugins.AppenderRefPlugin for element AppenderRef with params(ref="STDOUT")
2011-11-23 17:08:00,831 DEBUG Calling createLogger on class org.apache.logging.log4j.core.config.LoggerConfig${dollar}RootLogger for element root with params(additivity="null", level="error", AppenderRef={STDOUT}, null)
2011-11-23 17:08:00,833 DEBUG Calling createLoggers on class org.apache.logging.log4j.core.config.LoggersPlugin for element loggers with params(loggers={EventLogger, root})
2011-11-23 17:08:00,834 DEBUG Reconfiguration completed
2011-11-23 17:08:00,846 DEBUG Calling createLayout on class org.apache.logging.log4j.core.layout.PatternLayout for element PatternLayout with params(pattern="%d %p %c{1.} [%t] %m%n", Configuration(RoutingTest), null, charset="null")
2011-11-23 17:08:00,849 DEBUG Calling createPolicy on class org.apache.logging.log4j.core.appender.rolling.SizeBasedTriggeringPolicy for element SizeBasedTriggeringPolicy with params(size="500")
2011-11-23 17:08:00,851 DEBUG Calling createAppender on class org.apache.logging.log4j.core.appender.RollingFileAppender for element RollingFile with params(fileName="target/rolling1/rollingtest-Unknown.log", filePattern="target/rolling1/test1-Unknown.%i.log.gz", append="null", name="Rolling-Unknown", bufferedIO="null", immediateFlush="null", SizeBasedTriggeringPolicy(SizeBasedTriggeringPolicy(size=500)), null, PatternLayout(%d %p %c{1.} [%t] %m%n), null, ignoreExceptions="null")
2011-11-23 17:08:00,858 DEBUG Generated plugins in 0.002014000 seconds
2011-11-23 17:08:00,889 DEBUG Reconfiguration started for context sun.misc.Launcher${dollar}AppClassLoader@37b90b39
2011-11-23 17:08:00,890 DEBUG Generated plugins in 0.001355000 seconds
2011-11-23 17:08:00,959 DEBUG Generated plugins in 0.001239000 seconds
2011-11-23 17:08:00,961 DEBUG Generated plugins in 0.001197000 seconds
2011-11-23 17:08:00,965 WARN No Loggers were configured, using default
2011-11-23 17:08:00,976 DEBUG Reconfiguration completed</pre>
#end
          <p>
            If the status attribute is set to error than only error messages will be written to the console. This
            makes troubleshooting configuration errors possible. As an example, if the configuration above is changed
            to have the status set to error and the logger declaration is:</p>
          <pre class="prettyprint linenums"><![CDATA[
<logger name="EventLogger" level="info" additivity="false">
  <AppenderRef ref="Routng"/>
</logger>
]]></pre>
          <p>
            the following error message will be produced.
          </p>
          <pre>2011-11-24 23:21:25,517 ERROR Unable to locate appender Routng for logger EventLogger</pre>
          <p>
            Applications may wish to direct the status output to some other destination. This can be accomplished
            by setting the dest attribute to either "err" to send the output to stderr or to a file location or URL.
            This can also be done by insuring the configured status is set to OFF and then configuring the application
            programmatically such as:
          </p>
<pre class="prettyprint linenums"><![CDATA[
StatusConsoleListener listener = new StatusConsoleListener(Level.ERROR);
StatusLogger.getLogger().registerListener(listener);
]]></pre>
        </subsection>
        <a name="UnitTestingInMaven"/>
        <subsection name="Testing in Maven">
        <p>
          Maven can run unit and functional tests during the build cycle. By default, any files placed in
          <code>src/test/resources</code> are automatically copied to target/test-classes and are included
          in the classpath during execution of any tests. As such, placing a log4j2-test.xml into this directory
          will cause it to be used instead of a log4j2.xml or log4j2.json that might be present.  Thus a different
          log configuration can be used during testing than what is used in production.
        </p>
        <p>
          A second approach, which is extensively used by Log4j 2, is to set the log4j.configurationFile property
          in the method annotated with @BeforeClass in the junit test class. This will allow an arbitrarily
          named file to be used during the test.
        </p>
          <p>
            A third approach, also used extensively by Log4j 2, is to use the <code>LoggerContextRule</code>
            JUnit test rule which provides additional convenience methods for testing. This requires adding the
            <code>log4j-core</code> <code>test-jar</code> dependency to your test scope dependencies. For example:
          </p>
          <pre class="prettyprint linenums"><![CDATA[
public class AwesomeTest {
    @Rule
    public LoggerContextRule init = new LoggerContextRule("MyTestConfig.xml");

    @Test
    public void testSomeAwesomeFeature() {
        final LoggerContext ctx = init.getLoggerContext();
        final Logger logger = init.getLogger("org.apache.logging.log4j.my.awesome.test.logger");
        final Configuration cfg = init.getConfiguration();
        final ListAppender app = init.getListAppender("List");
        logger.warn("Test message");
        final List<LogEvent> events = app.getEvents();
        // etc.
    }
}
]]></pre>
        </subsection>
        <a name="SystemProperties"/>
        <subsection name="System Properties">
        <p>
          The Log4j documentation references a number of System Properties that can be used to control various aspects
          of Log4j 2 behavior. The table below lists these properties along with their default value and a
          description of what they control.
          Any spaces present in the property name are for visual flow and should be removed.
        </p>
          <p>
            Note that beginning in Log4j 2.10, all system property names have been normalized to follow a consistent
            naming scheme. While the old property names are still supported for backwards compatibility, it is
            recommended to update configurations to use the new style. This system is extensible and is enabled
            through the
            <a class="javadoc" href="../log4j-api/apidocs/org/apache/logging/log4j/util/PropertySource.html">PropertySource</a>
            interface. Additional property source classes can be added through the standard <code>ServiceLoader</code>
            mechanism in Java SE.
          </p>
          <p>
            Properties can be overridden by sources with a lower number priority (e.g.., -100 comes before 100). The
            following sources are all available by default:
          </p>
          <table>
            <caption align="top">PropertySource priorities and descriptions</caption>
            <tr>
              <th>Source</th>
              <th>Priority</th>
              <th>Description</th>
            </tr>
            <tr>
              <td>Environment Variables</td>
              <td>-100</td>
              <td>
                Environment variables are all prefixed with <code>LOG4J_</code>, are in all caps, and words are all
                separated by underscores. Only this naming scheme is support for environment variables as there were
                no old naming schemes to maintain compatibility with.
              </td>
            </tr>
            <tr>
              <td><code>log4j2.component.properties</code> file</td>
              <td>0</td>
              <td>
                Including this file on the classpath can be used as an alternative to providing properties as system
                properties. This has priority over system properties, but they can be overridden by environment
                variables as described above.
              </td>
            </tr>
            <tr>
              <td>System Properties</td>
              <td>100</td>
              <td>
                All properties can be set using normal system property patterns. These have the lowest priority and
                can be overridden by included properties files or environment variables.
              </td>
            </tr>
          </table>
          <p>
            The following is a list of available global configuration properties. Note that these can only be set once
            per JVM process unlike configuration settings available in configuration files. The <i>Property Name</i>
            column contains the name used in properties files and system properties; <i>Environemt Variable</i>
            for the equivalent environment variable; and <i>Legacy Property Name</i> for the pre-2.10 name.
          </p>
<style>
  * { // this works for all but td
  word-wrap:break-word;
  }

  table { // this somehow makes it work for td
  table-layout:fixed;
  width:100%;
  }
</style>
<table style="table-layout: fixed; width: 100%">
  <caption align="top">Log4j 2 global configuration properties</caption>
  <tr>
    <th>Property Name <br /> (Legacy Property Name)</th>
    <th>Environment Variable</th>
    <th>Default Value</th>
    <th>Description</th>
  </tr>

  <tr>
    <td><a name="configurationFile"/>log4j2.configurationFile
      <br />
      (<a name="log4j.configurationFile"/>log4j.configurationFile)
    </td>
    <td>LOG4J_CONFIGURATION_FILE</td>
    <td>&nbsp;</td>
    <td>
      Path to an Log4j 2 configuration file. May also contain a comma separated list of configuration file names.
    </td>
  </tr>
  <tr>
    <td><a name="debug"/>log4j2.debug
      <br />
      (<a name="log4j2.debug"/>log4j2.debug)
    </td>
    <td>LOG4J_DEBUG</td>
    <td>&nbsp;</td>
    <td>
      Log4j2 will print all internal logging to the console if system property
      <tt>log4j2.debug</tt> is defined (with any or no value).
    </td>
  </tr>
  <tr>
    <td><a name="mergeFactory"/>log4j2.mergeFactory
      <br />
      (<a name="log4j.mergeFactory"/>log4j.mergeFactory)
    </td>
    <td>LOG4J_MERGE_FACTORY</td>
    <td>&nbsp;</td>
    <td>
      The name of the class that implements the MergeStrategy interface. If not specified
      <code>DefaultMergeStrategy</code> will be used when creating a CompositeConfiguration..
    </td>
  </tr>
  <tr>
    <td><a name="contextSelector"/>log4j2.contextSelector
      <br />
      (<a name="Log4jContextSelector"/>Log4jContextSelector)
    </td>
    <td>LOG4J_CONTEXT_SELECTOR</td>
    <td>ClassLoaderContextSelector</td>
    <td>
      Creates the <tt>LoggerContext</tt>s. An application can have one or more active LoggerContexts depending
      on the circumstances.
      See <a href="logsep.html">Log Separation</a> for more details.
      Available context selector implementation classes:<br />
    <!-- deliberately inserted spaces to allow line break -->
      <tt>org.apache.logging.log4j.core.async .AsyncLoggerContextSelector</tt> - makes <a href="async.html">all loggers asynchronous</a>.<br />
      <tt>org.apache.logging.log4j.core.selector .BasicContextSelector</tt> - creates a single shared LoggerContext.<br />
      <tt>org.apache.logging.log4j.core.selector .ClassLoaderContextSelector</tt> - separate LoggerContexts for each web application.<br />
      <tt>org.apache.logging.log4j.core.selector .JndiContextSelector</tt> - use JNDI to locate each web application's LoggerContext.<br/>
      <tt>org.apache.logging.log4j.core.osgi .BundleContextSelector</tt> - separate LoggerContexts for each OSGi bundle.
    </td>
  </tr>
  <tr>
    <td><a name="logEventFactory"/>log4j2.logEventFactory
      <br />
      (<a name="Log4jLogEventFactory"/>Log4jLogEventFactory)
    </td>
    <td>LOG4J_LOG_EVENT_FACTORY</td>
    <!-- deliberately inserted spaces to allow line break -->
    <td>org.apache.logging.log4j.core.impl .DefaultLogEventFactory</td>
    <td>
      Factory class used by LoggerConfig to create <tt>LogEvent</tt> instances.
      (Ignored when the <tt>AsyncLoggerContextSelector</tt> is used.)
    </td>
  </tr>
  <tr>
    <td><a name="loggerContextFactory"/>log4j2.loggerContextFactory
      <br />
      (<a name="log4j2.loggerContextFactory"/>log4j2.loggerContextFactory)
    </td>
    <td>LOG4J_LOGGER_CONTEXT_FACTORY</td>
    <!-- deliberately inserted spaces to allow line break -->
    <td>org.apache.logging.log4j.simple .SimpleLoggerContextFactory</td>
    <td>
      Factory class used by LogManager to bootstrap the logging implementation.
      The core jar provides <tt>org.apache.logging.log4j.core
      .impl.Log4jContextFactory</tt>.
    </td>
  </tr>
  <tr>
    <td><a name="configurationFactory"/>log4j2.configurationFactory
      <br />
      (<a name="log4j.configurationFactory"/>log4j.configurationFactory)
    </td>
    <td>LOG4J_CONFIGURATION_FACTORY</td>
    <td>&nbsp;</td>
    <td>
      Fully specified class name of a class extending <tt>org.apache.logging.log4j.core
      .config.ConfigurationFactory</tt>.
      If specified, an instance of this class is added to the list of configuration factories.
    </td>
  </tr>
  <tr>
    <td><a name="shutdownHookEnabled"/>log4j2.shutdownHookEnabled
      <br />
      (<a name="log4j.shutdownHookEnabled"/>log4j.shutdownHookEnabled)
    </td>
    <td>LOG4J_SHUTDOWN_HOOK_ENABLED</td>
    <td>true</td>
    <td>
      Overrides the global flag for whether or not a shutdown hook should be used to stop a <tt>LoggerContext</tt>.
      By default, this is enabled and can be disabled on a per-configuration basis. When running with the
      <tt>log4j-web</tt> module, this is automatically disabled.
    </td>
  </tr>
  <tr>
    <td><a name="shutdownCallbackRegistry"/>log4j2.shutdownCallbackRegistry
      <br />
      (<a name="log4j.shutdownCallbackRegistry"/>log4j.shutdownCallbackRegistry)
    </td>
    <td>LOG4J_SHUTDOWN_CALLBACK_REGISTRY</td>
    <!-- deliberately inserted spaces to allow line break -->
    <td>org.apache.logging.log4j.core.util .DefaultShutdownCallbackRegistry</td>
    <td>
      Fully specified class name of a class implementing
      <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/util/ShutdownCallbackRegistry.html">ShutdownCallbackRegistry</a>.
      If specified, an instance of this class is used instead of <tt>DefaultShutdownCallbackRegistry</tt>.
      The specified class must have a default constructor.
    </td>
  </tr>
  <tr>
    <td><a name="clock"/>log4j2.clock
      <br />
      (<a name="log4j.Clock"/>log4j.Clock)
    </td>
    <td>LOG4J_CLOCK</td>
    <td>SystemClock</td>
    <td>
      Implementation of the <tt>org.apache.logging.log4j .core.util.Clock</tt>
      interface that is used for timestamping the log events.
      <br />
      By default, <tt>System.currentTimeMillis</tt> is called on every log event.
      <br />
      You can also specify a fully qualified class name of a custom class that implements the
      <tt>Clock</tt> interface.
    </td>
  </tr>
  <tr>
    <td><a name="enableJndiContextSelector"/>log4j2.enableJndiContextSelector</td>
    <td>LOG4J_ENABLE_JNDI_CONTEXT_SELECTOR</td>
    <td>false</td>
    <td>
      When true, the Log4j context selector that uses the JNDI java protocol is enabled. When false, the default, they are disabled.
    </td>
  </tr>
  <tr>
    <td><a name="enableJndiJdbc"/>log4j2.enableJndiJdbc</td>
    <td>LOG4J_ENABLE_JNDI_JDBC</td>
    <td>false</td>
    <td>
      When true, a Log4j JDBC Appender configured with a <code>DataSource</code> which uses JNDI's java protocol is enabled. When false, the default, they are disabled.
    </td>
  </tr>
  <tr>
    <td><a name="enableJndiJms"/>log4j2.enableJndiJms</td>
    <td>LOG4J_ENABLE_JNDI_JMS</td>
    <td>false</td>
    <td>
      When true, a Log4j JMS Appender that uses JNDI's java protocol is enabled. When false, the default, they are disabled.
    </td>
  </tr>
  <tr>
    <td><a name="enableJndiLookup"/>log4j2.enableJndiLookup</td>
    <td>LOG4J_ENABLE_JNDI_LOOKUP</td>
    <td>false</td>
    <td>
      When true, a Log4j lookup that uses JNDI's java protocol is enabled. When false, the default, they are disabled.
    </td>
  </tr>
  <tr>
    <td><a name="level"/>log4j2.level
      <br />
      (<a name="org.apache.logging.log4j.level"/>org.apache.logging.log4j.level)
    </td>
    <td>LOG4J_LEVEL</td>
    <td>ERROR</td>
    <td>
      Log level of the default configuration. The default configuration is used if the ConfigurationFactory
      could not successfully create a configuration (e.g. no log4j2.xml file was found).
    </td>
  </tr>
  <tr>
    <td><a name="disableThreadContext"/>log4j2.disableThreadContext
      <br />
      (disableThreadContext)
    </td>
    <td>LOG4J_DISABLE_THREAD_CONTEXT</td>
    <td>false</td>
    <td>
      If <tt>true</tt>, the ThreadContext stack and map are disabled.
      (May be ignored if a custom ThreadContext map is specified.)
    </td>
  </tr>
  <tr>
    <td><a name="disableThreadContextStack"/>log4j2.disableThreadContextStack
      <br />
      (disableThreadContextStack)
    </td>
    <td>LOG4J_DISABLE_THREAD_CONTEXT_STACK</td>
    <td>false</td>
    <td>
      If <tt>true</tt>, the ThreadContext stack is disabled.
    </td>
  </tr>
  <tr>
    <td><a name="disableThreadContextMap"/>log4j2.disableThreadContextMap
      <br />
      (disableThreadContextMap)
    </td>
    <td>LOG4J_DISABLE_THREAD_CONTEXT_MAP</td>
    <td>false</td>
    <td>
      If <tt>true</tt>, the ThreadContext map is disabled.
      (May be ignored if a custom ThreadContext map is specified.)
    </td>
  </tr>
  <tr>
    <td><a name="log4j2.threadContextMap"/>log4j2.threadContextMap
      <br />
      (log4j2.threadContextMap)
    </td>
    <td>LOG4J_THREAD_CONTEXT_MAP</td>
    <td>&nbsp;</td>
    <td>
      Fully specified class name of a custom <tt>ThreadContextMap</tt> implementation class.
    </td>
  </tr>
  <tr>
    <td><a name="isThreadContextMapInheritable"/>log4j2.isThreadContextMapInheritable
      <br />
      (isThreadContextMapInheritable)
    </td>
    <td>LOG4J_IS_THREAD_CONTEXT_MAP_INHERITABLE</td>
    <td>false</td>
    <td>
      If <tt>true</tt> use a <tt>InheritableThreadLocal</tt> to implement the ThreadContext map.
      Otherwise, use a plain <tt>ThreadLocal</tt>.
      (May be ignored if a custom ThreadContext map is specified.)
    </td>
  </tr>
  <tr>
    <td><a name="contextDataInjector"/>log4j2.contextDataInjector
      <br />
      (<a name="log4j2.ContextDataInjector"/>log4j2.ContextDataInjector)
    </td>
    <td>LOG4J_CONTEXT_DATA_INJECTOR</td>
    <td>&nbsp;</td>
    <td>
      Fully specified class name of a custom <tt>ContextDataInjector</tt> implementation class.
    </td>
  </tr>
  <tr>
    <td><a name="garbagefreeThreadContextMap"/>log4j2.garbagefreeThreadContextMap
      <br />
      (<a name="log4j2.garbagefree.threadContextMap"/>log4j2.garbagefree.threadContextMap)
    </td>
    <td>LOG4J_GARBAGEFREE_THREAD_CONTEXT_MAP</td>
    <td>false</td>
    <td>
      Specify "true" to make the ThreadContext map garbage-free.
    </td>
  </tr>
  <tr>
    <td><a name="disableJmx"/>log4j2.disableJmx
      <br />
      (<a name="log4j2.disable.jmx"/>log4j2.disable.jmx)
    </td>
    <td>LOG4J_DISABLE_JMX</td>
    <td>false</td>
    <td>
      If <tt>true</tt>, Log4j configuration objects like LoggerContexts, Appenders, Loggers, etc.
      will not be instrumented with MBeans and cannot be remotely monitored and managed.
    </td>
  </tr>
  <tr>
    <td><a name="jmxNotifyAsync"/>log4j2.jmxNotifyAsync
      <br />
      (<a name="log4j2.jmx.notify.async"/>log4j2.jmx.notify.async)
    </td>
    <td>LOG4J_JMX_NOTIFY_ASYNC</td>
    <td>false for web apps, true otherwise</td>
    <td>
      If <tt>true</tt>, log4j's JMX notifications are sent from a separate background thread,
      otherwise they are sent from the caller thread.
      If system property <tt>log4j2.is.webapp</tt> is <tt>true</tt> or the <tt>javax.servlet.Servlet</tt>
      class is on the classpath, the default behaviour
      is to use the caller thread to send JMX notifications.
    </td>
  </tr>
  <tr>
    <td><a name="skipJansi"/>log4j2.skipJansi
      <br />
      (<a name="log4j.skipJansi"/>log4j.skipJansi)
    </td>
    <td>LOG4J_SKIP_JANSI</td>
    <td>true</td>
    <td>
      If <tt>true</tt>, the ConsoleAppender will not try to use the Jansi output stream on Windows.
    </td>
  </tr>
  <tr>
    <td><a name="ignoreTCL"/>log4j2.ignoreTCL
      <br />
      (<a name="log4j.ignoreTCL"/>log4j.ignoreTCL)
    </td>
    <td>LOG4J_IGNORE_TCL</td>
    <td>false</td>
    <td>
      If <tt>true</tt>, classes are only loaded with the default class loader.
      Otherwise, an attempt is made to load classes with the current thread's context class loader
      before falling back to the default class loader.
    </td>
  </tr>
  <tr>
    <td><a name="uuidSequence"/>log4j2.uuidSequence
      <br />
      (<a name="org.apache.logging.log4j.uuidSequence"/>org.apache.logging.log4j.uuidSequence)
    </td>
    <td>LOG4J_UUID_SEQUENCE</td>
    <td>0</td>
    <td>
      System property that may be used to seed the UUID generation with an integer value.
    </td>
  </tr>
  <!--
  <tr>
    <td><a name="assignedSequences">log4j2.assignedSequences</td>
    <td>LOG4J_ASSIGNED_SEQUENCES</td>
    <td><a name="org.apache.logging.log4j.assignedSequences"/>org.apache.logging.log4j.assignedSequences</td>
    <td>true</td>
    <td>
      TODO: used to seed UUID generation. Not sure when or why one would use this...
    </td>
  </tr>
  -->
  <tr>
    <td><a name="simplelogShowContextMap"/>log4j2.simplelogShowContextMap
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.showContextMap"/>org.apache.logging.log4j .simplelog.showContextMap)
    </td>
    <td>LOG4J_SIMPLELOG_SHOW_CONTEXT_MAP</td>
    <td>false</td>
    <td>If <tt>true</tt>, the full ThreadContext map is included in each SimpleLogger log message.</td>
  </tr>
  <tr>
    <td><a name="simplelogShowlogname"/>log4j2.simplelogShowlogname
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.showlogname"/>org.apache.logging.log4j .simplelog.showlogname)
    </td>
    <td>LOG4J_SIMPLELOG_SHOWLOGNAME</td>
    <td>false</td>
    <td>If <tt>true</tt>, the logger name is included in each SimpleLogger log message.</td>
  </tr>
  <tr>
    <td><a name="simplelogShowShortLogname"/>log4j2.simplelogShowShortLogname
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.showShortLogname"/>org.apache.logging.log4j  .simplelog.showShortLogname)
    </td>
    <td>LOG4J_SIMPLELOG_SHOW_SHORT_LOGNAME</td>
    <td>true</td>
    <td>If <tt>true</tt>, only the last component of a logger name is included in SimpleLogger log messages.
    (E.g., if the logger name is "mycompany.myproject.mycomponent", only "mycomponent" is logged.
    </td>
  </tr>
  <tr>
    <td><a name="simplelogShowdatetime"/>log4j2.simplelogShowdatetime
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.showdatetime"/>org.apache.logging.log4j .simplelog.showdatetime)
    </td>
    <td>LOG4J_SIMPLELOG_SHOWDATETIME</td>
    <td>false</td>
    <td>If <tt>true</tt>, SimpleLogger log messages contain timestamp information.
    </td>
  </tr>
  <tr>
    <td><a name="simplelogDateTimeFormat"/>log4j2.simplelogDateTimeFormat
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.dateTimeFormat"/>org.apache.logging.log4j .simplelog.dateTimeFormat)
    </td>
    <td>LOG4J_SIMPLELOG_DATE_TIME_FORMAT</td>
    <td>"yyyy/MM/dd HH:mm:ss:SSS zzz"</td>
    <td>Date-time format to use.
    Ignored if <tt>org.apache.logging.log4j .simplelog.showdatetime</tt> is <tt>false</tt>.
    </td>
  </tr>
  <tr>
    <td><a name="simplelogLogFile"/>log4j2.simplelogLogFile
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.logFile"/>org.apache.logging.log4j .simplelog.logFile)
    </td>
    <td>LOG4J_SIMPLELOG_LOG_FILE</td>
    <td>system.err</td>
    <td>"system.err" (case-insensitive) logs to System.err,
    "system.out" (case-insensitive) logs to System.out,
    any other value is interpreted as a file name to save SimpleLogger messages to.
    </td>
  </tr>
  <tr>
    <td><a name="simplelogLevel"/>log4j2.simplelogLevel
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.level"/>org.apache.logging.log4j .simplelog.level)
    </td>
    <td>LOG4J_SIMPLELOG_LEVEL</td>
    <td>ERROR</td>
    <td>Default level for new SimpleLogger instances.
    </td>
  </tr>
  <tr>
    <td>log4j2.simplelog.&lt;loggerName&gt;.level
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.[loggerName]level"/>org.apache.logging.log4j .simplelog.&lt;loggerName&gt;.level)
    </td>
    <td>LOG4J_SIMPLELOG_&lt;LOGGER_NAME&gt;_LEVEL</td>
    <td>SimpleLogger default log level</td>
    <td>Log level for a the SimpleLogger instance with the specified name.</td>
  </tr>
  <tr>
    <td><a name="simplelogStatusLoggerLevel"/>log4j2.simplelogStatusLoggerLevel
      <br />
      <!-- deliberately inserted spaces to allow line break -->
      (<a name="org.apache.logging.log4j.simplelog.StatusLogger.level" />org.apache.logging.log4j.simplelog .StatusLogger.level)
    </td>
    <td>LOG4J_SIMPLELOG_STATUS_LOGGER_LEVEL</td>
    <td>ERROR</td>
    <td>This property is used to control the initial StatusLogger level, and can be overridden in code by calling
    <code>StatusLogger.getLogger() .setLevel(someLevel)</code>.
    Note that the StatusLogger level is only used to determine the status log output level
    until a listener is registered. In practice, a listener is registered when a configuration is found,
    and from that point onwards, status messages are only sent to the listeners (depending on their statusLevel).</td>
  </tr>
  <tr>
    <td><a name="defaultStatusLevel"/>log4j2.defaultStatusLevel
      <br />
      (<a name="Log4jDefaultStatusLevel" />Log4jDefaultStatusLevel)
    </td>
    <td>LOG4J_DEFAULT_STATUS_LEVEL</td>
    <td>ERROR</td>
    <td>
      <p>The StatusLogger logs events that occur in the logging system to the console.
      During configuration, AbstractConfiguration registers a StatusConsoleListener with the StatusLogger that may
      redirect status log events from the default console output to a file.
      The listener also supports fine-grained filtering.
      This system property specifies the default status log level for the listener to use if the configuration does not
      specify a status level.
      </p><p>
      Note: this property is used by the log4j-core implementation only after a configuration file has been found.</p>
    </td>
  </tr>
  <tr>
    <td><a name="statusLoggerLevel"/>log4j2.statusLoggerLevel
      <br />
      (<a name="log4j2.StatusLogger.level"/>log4j2.StatusLogger.level)
    </td>
    <td>LOG4J_STATUS_LOGGER_LEVEL</td>
    <td>WARN</td>
    <td>
      <p>The initial "listenersLevel" of the StatusLogger. If StatusLogger listeners are added, the "listenerLevel"
      is changed to that of the most verbose listener. If any listeners are registered, the listenerLevel is
      used to quickly determine if an interested listener exists.
      </p><p>
      By default, StatusLogger listeners are added when a configuration is found and by the JMX
      StatusLoggerAdmin MBean. For example, if a configuration contains
      <code>&lt;Configuration status="trace"&gt;</code>, a listener with statusLevel TRACE is registered
      and the StatusLogger listenerLevel is set to TRACE, resulting in verbose status messages displayed on the console.
      </p><p>
      If no listeners are registered, the listenersLevel is not used, and the StatusLogger output level
      is determined by <code>StatusLogger.getLogger().getLevel()</code>
      (see property <code>org.apache.logging.log4j.simplelog .StatusLogger.level</code>).</p>
    </td>
  </tr>
  <tr>
    <td><a name="statusEntries"/>log4j2.statusEntries
      <br />
      (<a name="log4j2.status.entries"/>log4j2.status.entries)
    </td>
    <td>LOG4J_STATUS_ENTRIES</td>
    <td>200</td>
    <td>
      Number of StatusLogger events that are kept in a buffer and can be retrieved with
      <tt>StatusLogger.getStatusData()</tt>.
    </td>
  </tr>
  <tr>
    <td><a name="statusLoggerDateformat"/>log4j2.statusLoggerDateformat
      <br />
      (<a name="log4j2.StatusLogger.DateFormat"/>log4j2.StatusLogger.DateFormat)
    </td>
    <td>LOG4J_STATUS_LOGGER_DATEFORMAT</td>
    <td>&nbsp;</td>
    <td>
      Date-time format string to use as the format for timestamps
      in the status logger output. See <code>java.text.SimpleDateFormat</code> for supported formats.
    </td>
  </tr>
  <tr>
    <td><a name="asyncLoggerExceptionHandler"/>log4j2.asyncLoggerExceptionHandler
      <br />
      (<a name="AsyncLogger.ExceptionHandler"/>AsyncLogger.ExceptionHandler)
    </td>
    <td>LOG4J_ASYNC_LOGGER_EXCEPTION_HANDLER</td>
    <td>default handler</td>
    <td>
      See <a href="async.html#SysPropsAllAsync">Async Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="asyncLoggerRingBufferSize"/>log4j2.asyncLoggerRingBufferSize
      <br />
      (<a name="AsyncLogger.RingBufferSize"/>AsyncLogger.RingBufferSize)
    </td>
    <td>LOG4J_ASYNC_LOGGER_RING_BUFFER_SIZE</td>
    <td>256&#160;*&#160;1024</td>
    <td>
      See <a href="async.html#SysPropsAllAsync">Async Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="asyncLoggerWaitStrategy"/>log4j2.asyncLoggerWaitStrategy
      <br />
      (<a name="AsyncLogger.WaitStrategy" />AsyncLogger.WaitStrategy)
    </td>
    <td>LOG4J_ASYNC_LOGGER_WAIT_STRATEGY</td>
    <td>
      Timeout
    </td>
    <td>
      See <a href="async.html#SysPropsAllAsync">Async Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="AsyncLogger.SynchronizeEnqueueWhenQueueFull"/>AsyncLogger.SynchronizeEnqueueWhenQueueFull
    </td>
    <td>ASYNC_LOGGER_SYNCHRONIZE_ENQUEUE_WHEN_QUEUE_FULL</td>
    <td>
      true
    </td>
    <td>
      See <a href="async.html#SysPropsAllAsync">Async Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="asyncLoggerThreadNameStrategy"/>log4j2.asyncLoggerThreadNameStrategy
      <br />
      (<a name="AsyncLogger.ThreadNameStrategy"/>AsyncLogger.ThreadNameStrategy)
    </td>
    <td>LOG4J_ASYNC_LOGGER_THREAD_NAME_STRATEGY</td>
    <td>
      CACHED
    </td>
    <td>
      See <a href="async.html#SysPropsAllAsync">Async Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="asyncLoggerConfigExceptionHandler"/>log4j2.asyncLoggerConfigExceptionHandler
      <br />
      (<a name="AsyncLoggerConfig.ExceptionHandler"/>AsyncLoggerConfig.ExceptionHandler)
    </td>
    <td>LOG4J_ASYNC_LOGGER_CONFIG_EXCEPTION_HANDLER</td>
    <td>default handler</td>
    <td>
      See <a href="async.html#SysPropsMixedSync-Async">Mixed Async/Synchronous Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="asyncLoggerConfigRingBufferSize"/>log4j2.asyncLoggerConfigRingBufferSize
      <br />
      (<a name="AsyncLoggerConfig.RingBufferSize"/>AsyncLoggerConfig.RingBufferSize)
    </td>
    <td>LOG4J_ASYNC_LOGGER_CONFIG_RING_BUFFER_SIZE</td>
    <td>256&#160;*&#160;1024</td>
    <td>
      See <a href="async.html#SysPropsMixedSync-Async">Mixed Async/Synchronous Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="asyncLoggerConfigWaitStrategy"/>log4j2.asyncLoggerConfigWaitStrategy
      <br />
      (<a name="AsyncLoggerConfig.WaitStrategy"/>AsyncLoggerConfig.WaitStrategy)
    </td>
    <td>LOG4J_ASYNC_LOGGER_CONFIG_WAIT_STRATEGY</td>
    <td>
      Timeout
    </td>
    <td>
      See <a href="async.html#SysPropsMixedSync-Async">Mixed Async/Synchronous Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="AsyncLoggerConfig.SynchronizeEnqueueWhenQueueFull"/>AsyncLoggerConfig.SynchronizeEnqueueWhenQueueFull
    </td>
    <td>ASYNC_LOGGER_CONFIG_SYNCHRONIZE_ENQUEUE_WHEN_QUEUE_FULL</td>
    <td>
      true
    </td>
    <td>
      See <a href="async.html#SysPropsMixedSync-Async">Mixed Async/Synchronous Logger System Properties</a> for details.
    </td>
  </tr>
  <tr>
    <td><a name="julLoggerAdapter"/>log4j2.julLoggerAdapter
      <br />
      (<a name="log4j.jul.LoggerAdapter"/>log4j.jul.LoggerAdapter)
    </td>
    <td>LOG4J_JUL_LOGGER_ADAPTER</td>
    <!-- deliberately inserted spaces to allow line break -->
    <td>org.apache.logging.log4j .jul.ApiLoggerAdapter</td>
    <td>
      Default LoggerAdapter to use in the JUL adapter. By default, if log4j-core is available, then the class
      <code>org.apache.logging.log4j.jul .CoreLoggerAdapter</code> will be used. Otherwise, the
      <code>ApiLogggerAdapter</code> will be used. Custom implementations must provide a public default constructor.
    </td>
  </tr>
  <tr>
    <td><a name="formatMsgAsync"/>log4j2.formatMsgAsync
      <br />
      (<a name="log4j.format.msg.async"/>log4j.format.msg.async)
    </td>
    <td>LOG4J_FORMAT_MSG_ASYNC</td>
    <td>
      false
    </td>
    <td>
      If <tt>false</tt> (the default), Log4j will make sure the message is formatted in the caller thread, to ensure
      the value at the time of the call to the logger is the value that is logged.
    </td>
  </tr>
  <tr>
    <td><a name="asyncQueueFullPolicy"/>log4j2.asyncQueueFullPolicy
      <br />
      (<a name="log4j2.AsyncQueueFullPolicy"/>log4j2.AsyncQueueFullPolicy)
    </td>
    <td>LOG4J_ASYNC_QUEUE_FULL_POLICY</td>
    <td>&nbsp;</td>
    <td>
      <p>Used by Async Loggers and the AsyncAppender to maintain application throughput even when
        the underlying appender cannot keep up with the logging rate and the queue is filling up.</p>
      <p>If no value is specified (the default) events are never discarded. If the queue is full, the
        logger call blocks until the event can be added to the queue.</p>
      <p>Specify <tt>Discard</tt> to drop events whose level is equal or less than the threshold level
        (INFO by default) when the queue is full.</p>
    </td>
  </tr>
  <tr>
    <td><a name="discardThreshold"/>log4j2.discardThreshold
      <br />
      (<a name="log4j2.DiscardThreshold"/>log4j2.DiscardThreshold)
    </td>
    <td>LOG4J_DISCARD_THRESHOLD</td>
    <td>INFO</td>
    <td>Used by the DiscardingAsyncQueueFullPolicy to determine which events to drop when the queue
      becomes full. By default, <tt>INFO</tt>, <tt>DEBUG</tt> and <tt>TRACE</tt> level
      events are discarded when the queue is full.
      This property only has effect if <tt>Discard</tt> is specified as the
      <tt>log4j2.AsyncQueueFullPolicy</tt>.</td>
  </tr>
  <tr>
    <td><a name="messageFactory"/>log4j2.messageFactory
      <br />
      (<a name="log4j2.messageFactory" />log4j2.messageFactory)
    </td>
    <td>LOG4J_MESSAGE_FACTORY</td>
    <td>org.apache.logging.log4j.message. ParameterizedMessageFactory or
      org.apache.logging.log4j.message. ReusableMessageFactory in garbage-free mode</td>
    <td>Default message factory used by Loggers if no factory was specified.</td>
  </tr>
  <tr>
    <td><a name="flowMessageFactory"/>log4j2.flowMessageFactory
      <br />
      (<a name="log4j2.flowMessageFactory" />log4j2.flowMessageFactory)
    </td>
    <td>LOG4J_FLOW_MESSAGE_FACTORY</td>
    <td>org.apache.logging.log4j.message. DefaultFlowMessageFactory</td>
    <td>Default flow message factory used by Loggers.</td>
  </tr>
  <tr>
    <td><a name="isWebapp"/>log4j2.isWebapp
      <br />
      (<a name="log4j2.is.webapp"/>log4j2.is.webapp)
    </td>
    <td>LOG4J_IS_WEBAPP</td>
    <td>true if <tt>Servlet</tt> class on class path </td>
    <td>This system property can be used to force Log4j 2 to behave as if it is part of a web application (when true)
    or as if it is not part of a web application (when false).</td>
  </tr>
  <tr>
    <td><a name="enableThreadlocals"/>log4j2.enableThreadlocals
      <br />
      (<a name="log4j2.enable.threadlocals" />log4j2.enable.threadlocals)
    </td>
    <td>LOG4J_ENABLE_THREADLOCALS</td>
    <td>true</td>
    <td>This system property can be used to switch off the use of threadlocals, which will partly disable
      Log4j's garbage-free behaviour: to be fully garbage-free, Log4j stores
      objects in ThreadLocal fields to reuse them, otherwise new objects are created for each log event.
      Note that this property is not effective when Log4j detects it is running in a web application.</td>
  </tr>
  <tr>
    <td><a name="enableDirectEncoders"/>log4j2.enableDirectEncoders
      <br />
      (<a name="log4j2.enable.direct.encoders" />log4j2.enable.direct.encoders)
    </td>
    <td>LOG4J_ENABLE_DIRECT_ENCODERS</td>
    <td>true</td>
    <td>This property can be used to force garbage-aware Layouts and Appenders to revert to the
      pre-2.6 behaviour where converting log events to text generates temporary objects like
      Strings and char[] arrays, and converting this text to bytes generates temporary byte[] arrays.
      By default, this property is <tt>true</tt> and garbage-aware Layouts and Appenders that convert log events
      to text will convert this text to bytes without creating temporary objects.</td>
  </tr>
  <tr>
    <td><a name="initialReusableMsgSize"/>log4j2.initialReusableMsgSize
      <br />
      (<a name="log4j.initialReusableMsgSize" />log4j.initialReusableMsgSize)
    </td>
    <td>LOG4J_INITIAL_REUSABLE_MSG_SIZE</td>
    <td>128</td>
    <td>In GC-free mode, this property determines the initial size of the reusable StringBuilders where the message
     text is formatted and potentially passed to background threads.</td>
  </tr>
  <tr>
    <td><a name="maxReusableMsgSize"/>log4j2.maxReusableMsgSize
      <br />
      (<a name="log4j.maxReusableMsgSize" />log4j.maxReusableMsgSize)
    </td>
    <td>LOG4J_MAX_REUSABLE_MSG_SIZE</td>
    <td>518</td>
    <td>In GC-free mode, this property determines the maximum size of the reusable StringBuilders where the message
     text is formatted and potentially passed to background threads.</td>
  </tr>
  <tr>
    <td><a name="layoutStringBuilderMaxSize"/>log4j2.layoutStringBuilderMaxSize
      <br />
      (<a name="log4j.layoutStringBuilder.maxSize" />log4j.layoutStringBuilder.maxSize)
    </td>
    <td>LOG4J_LAYOUT_STRING_BUILDER_MAX_SIZE</td>
    <td>2048</td>
    <td>This property determines the maximum size of the thread-local reusable StringBuilders
     used to format the log event to text by Layouts that extend AbstractStringLayout.</td>
  </tr>
  <tr>
    <td><a name="unboxRingbufferSize"/>log4j2.unboxRingbufferSize
      <br />
      (<a name="log4j.unbox.ringbuffer.size" />log4j.unbox.ringbuffer.size)
    </td>
    <td>LOG4J_UNBOX_RINGBUFFER_SIZE</td>
    <td>32</td>
    <td>The <tt>org.apache.logging.log4j.util.Unbox</tt> utility
    manages a small thread-local ring buffer of StringBuilders.
     Each time one of the <tt>box()</tt> methods is called, the next slot in the ring buffer is used, until the ring
     buffer is full and the first slot is reused. By default the Unbox ring buffer has 32 slots, so user code can
     have up to 32 boxed primitives in a single logger call.
     <p>
     If more slots are required, set system property <tt>log4j.unbox.ringbuffer.size</tt> to the desired ring buffer size.
     Note that the specified number will be rounded up to the nearest power of 2.</p></td>
  </tr>
  <tr>
    <td><a name="loggerContextStacktraceOnStart"/>log4j2.loggerContextStacktraceOnStart
      <br />
      (<a name="log4j.LoggerContext.stacktrace.on.start" />log4j.LoggerContext.stacktrace.on.start)
    </td>
    <td>LOG4J_LOGGER_CONTEXT_STACKTRACE_ON_START</td>
    <td>false</td>
    <td>Prints a stacktrace to the <a href="#StatusMessages">status logger</a> at DEBUG level
    when the LoggerContext is started. For debug purposes.</td>
  </tr>
  <tr>
      <td><a name="formatMsgNoLookups"/>log4j2.formatMsgNoLookups
        <br />
        (<a name="log4j2.formatMsgNoLookups" />log4j2.formatMsgNoLookups)
      </td>
      <td>FORMAT_MESSAGES_PATTERN_DISABLE_LOOKUPS</td>
      <td>false</td>
      <td>Disables message pattern lookups globally when set to <tt>true</tt>.
          This is equivalent to defining all message patterns using <tt>%m{nolookups}</tt>.</td>
  </tr>
  <tr>
    <td><a name="log4j2.trustStoreLocation "/>log4j2.trustStoreLocation</td>
    <td>LOG4J_TRUST_STORE_LOCATION</td>
    <td></td>
    <td>The location of the trust store. If not provided the default trust store will be used.</td>
  </tr>
  <tr>
    <td><a name="log4j2.trustStorePassword"/>log4j2.trustStorePassword</td>
    <td>LOG4J_TRUST_STORE_PASSWORD</td>
    <td></td>
    <td>Password needed to access the trust store.</td>
  </tr>
  <tr>
    <td><a name="log4j2.trustStorePasswordFile"/>log4j2.trustStorePasswordFile</td>
    <td>LOG4J_TRUST_STORE_PASSWORD_FILE</td>
    <td></td>
    <td>The location of a file that contains the password for the trust store.</td>
  </tr>
  <tr>
    <td><a name="log4j2.trustStorePasswordEnvironmentVariable"/>log4j2.trustStorePasswordEnvironmentVariable</td>
    <td>LOG4J_TRUST_STORE_PASSWORD_ENVIRONMENT_VARIABLE</td>
    <td></td>
    <td>The name of the environment variable that contains the trust store password.</td>
  </tr>
  <tr>
    <td><a name="log4j2.trustStoreType"/>log4j2.trustStoreType</td>
    <td>LOG4J_TRUST_STORE_TYPE</td>
    <td></td>
    <td>The type of key store used for the trust store.</td>
  </tr>
  <tr>
    <td><a name="log4j2.trustStoreKeyManagerFactoryAlgorithm"/>log4j2.trustStoreKeyManagerFactoryAlgorithm</td>
    <td>LOG4J_TRUST_STORE_KEY_MANAGER_FACTORY_ALGORITHM</td>
    <td></td>
    <td>Java cryptographic algorithm.</td>
  </tr>
  <tr>
    <td><a name="log4j2.keyStoreLocation "/>log4j2.keyStoreLocation </td>
    <td>LOG4J_KEY_STORE_LOCATION</td>
    <td></td>
    <td>The location of the key store. If not provided the default key store will be used.</td>
  </tr>
  <tr>
    <td><a name="log4j2.keyStorePassword"/>log4j2.keyStorePassword</td>
    <td>LOG4J_KEY_STORE_PASSWORD</td>
    <td></td>
    <td>Password needed to access the key store.</td>
  </tr>
  <tr>
    <td><a name="log4j2.keyStorePasswordFile"/>log4j2.keyStorePasswordFile</td>
    <td>LOG4J_KEY_STORE_PASSWORD_FILE</td>
    <td></td>
    <td>The location of a file that contains the password for the key store.</td>
  </tr>
  <tr>
    <td><a name="log4j2.keyStorePasswordEnvironmentVariable"/>log4j2.keyStorePasswordEnvironmentVariable</td>
    <td>LOG4J_KEY_STORE_PASSWORD_ENVIRONMENT_VARIABLE</td>
    <td></td>
    <td>The name of the environment variable that contains the key store password.</td>
  </tr>
  <tr>
    <td><a name="log4j2.keyStoreType"/>log4j2.keyStoreType</td>
    <td>LOG4J_KEY_STORE_TYPE</td>
    <td></td>t
    <td>The type of key store.</td>
  </tr>
  <tr>
    <td><a name="log4j2.keyStoreKeyManagerFactoryAlgorithm"/>log4j2.keyStoreKeyManagerFactoryAlgorithm</td>
    <td>LOG4J_KEY_STORE_KEY_MANAGER_FACTORY_ALGORITHM</td>
    <td></td>
    <td>Java cryptographic algorithm.</td>
  </tr>
  <tr>
    <td><a name="log4j2.sslVerifyHostName"/>log4j2.sslVerifyHostName</td>
    <td></td>
    <td>false</td>
    <td>true or false if the host name should be verified</td>
  </tr>
</table>

        </subsection>
      </section>
    </body>
</document>
