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<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>Migrating from Log4j 1.x</title>
        <author email="rgoers@apache.org">Ralph Goers</author>
    </properties>

    <body>
        <section name="Migrating from Log4j 1.x">
          <a name="Log4j1.2Bridge"/>
          <subsection name="Using the Log4j 1.x bridge">
            <p>
              Perhaps the simplest way to convert to using Log4j 2 is to replace the log4j 1.x jar file with
              Log4j 2's <code>log4j-1.2-api.jar</code>. However, to use this successfully applications must meet the
              following requirements:
            </p>
              <ol>
                <li>They must not access methods and classes internal to the Log4j 1.x implementation such
                  as <code>Appender</code>s, <code>LoggerRepository</code> or <code>Category</code>'s
                  <code>callAppenders</code> method.</li>
                <li>They must not programmatically configure Log4j.</li>
                <li>They must not configure by calling the classes <code>DOMConfigurator</code> or
                  <code>PropertyConfigurator</code>.</li>
              </ol>
          </subsection>
          <subsection name="Converting to the Log4j 2 API">
            <p>For the most part, converting from the Log4j 1.x API to Log4j 2 should be fairly simple. Many
              of the log statements will require no modification. However, where necessary the following changes must be
              made.</p>
              <ol>
                <li>
                  The main package in version 1 is <code>org.apache.log4j</code>, in version 2 it is
                  <code>org.apache.logging.log4j</code>
                </li>
                <li>
                  Calls to <code>org.apache.log4j.Logger.getLogger()</code> must be modified to
                  <code>org.apache.logging.log4j.LogManager.getLogger()</code>.
                </li>
                <li>
                  Calls to <code>org.apache.log4j.Logger.getRootLogger()</code> or
                  <code>org.apache.log4j.LogManager.getRootLogger()</code> must be replaced with
                  <code>org.apache.logging.log4j.LogManager.getRootLogger()</code>.</li>
                <li>
                  Calls to <code>org.apache.log4j.Logger.getLogger</code> that accept a <code>LoggerFactory</code> must
                  remove the <code>org.apache.log4j.spi.LoggerFactory</code> and use one of Log4j 2's other extension
                  mechanisms.
                </li>
                <li>
                  Replace calls to <code>org.apache.log4j.Logger.getEffectiveLevel()</code> with
                  <code>org.apache.logging.log4j.Logger.getLevel()</code>.
                </li>
                <li>
                  Remove calls to <code>org.apache.log4j.LogManager.shutdown()</code>, they are not needed in version 2
                  because the Log4j Core now automatically adds a JVM shutdown hook on start up to perform any Core
                  clean ups.
                  <ol>
                    <li>
                      Starting in Log4j 2.1, you can specify a custom
                      <a class="javadoc" href="../log4j-core/apidocs/org/apache/logging/log4j/core/util/ShutdownCallbackRegistry.html">ShutdownCallbackRegistry</a>
                      to override the default JVM shutdown hook strategy.
                    </li>
                    <li>
                      Starting in Log4j 2.6, you can now use <code>org.apache.logging.log4j.LogManager.shutdown()</code>
                      to initiate shutdown manually.
                    </li>
                  </ol>
                </li>
                <li>
                  Calls to <code>org.apache.log4j.Logger.setLevel()</code> or similar methods are not supported in the API.
                  Applications should remove these. Equivalent functionality is provided in the Log4j 2 implementation
                  classes, see <code>org.apache.logging.log4j.core.config.Configurator.setLevel()</code>, but may leave 
                  the application susceptible to changes in Log4j 2 internals.                   
                </li>
                <li>
                  Where appropriate, applications should convert to use parameterized messages instead of String
                  concatenation.
                </li>
                <li>
                  <a href="http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/MDC.html"><code>org.apache.log4j.MDC</code></a> and
                  <a href="http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/NDC.html"><code>org.apache.log4j.NDC</code></a>
                  have been replaced by the <a href="thread-context.html">Thread Context</a>.
                </li>
              </ol>
          </subsection>
          <subsection name="Configuring Log4j 2">
            <p>
              Although the Log4j 2 configuration syntax is different than that of Log4j 1.x, most, if not all, of
              the same functionality is available.
            </p>
            <p>
              Note that system property interpolation via the <code>${foo}</code> syntax has been extended to allow
              property lookups from many different sources. See the <a href="lookups.html">Lookups</a> documentation
              for more details. For example, using a lookup for the system property named <code>catalina.base</code>,
              in Log4j 1.x, the syntax would be <code>${catalina.base}</code>. In Log4j 2, the syntax would be
              <code>${sys:catalina.base}</code>.
            </p>
            <p>
              Below are the example configurations for Log4j 1.x and their counterparts in Log4j 2.
            </p>

            <h4>Sample 1 - Simple configuration using a Console Appender</h4>
            <p>Log4j 1.x XML configuration</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration PUBLIC "-//APACHE//DTD LOG4J 1.2//EN" "log4j.dtd">
<log4j:configuration xmlns:log4j='http://jakarta.apache.org/log4j/'>
  <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </layout>
  </appender>
  <category name="org.apache.log4j.xml">
    <priority value="info" />
  </category>
  <Root>
    <priority value ="debug" />
    <appender-ref ref="STDOUT" />
  </Root>
</log4j:configuration>]]></pre>
            <p>Log4j 2 XML configuration</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
  <Appenders>
    <Console name="STDOUT" target="SYSTEM_OUT">
      <PatternLayout pattern="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Logger name="org.apache.log4j.xml" level="info"/>
    <Root level="debug">
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>
</Configuration>]]></pre>

            <h4>Sample 2 - Simple configuration using a File Appender</h4>
            <p>Log4j 1.x XML configuration</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration PUBLIC "-//APACHE//DTD LOG4J 1.2//EN" "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
  <appender name="A1" class="org.apache.log4j.FileAppender">
    <param name="File"   value="A1.log" />
    <param name="Append" value="false" />
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%t %-5p %c{2} - %m%n"/>
    </layout>
  </appender>
  <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </layout>
  </appender>
  <category name="org.apache.log4j.xml">
    <priority value="debug" />
    <appender-ref ref="A1" />
  </category>
  <root>
    <priority value ="debug" />
    <appender-ref ref="STDOUT" />
  </Root>
</log4j:configuration>]]></pre>

           <p>Log4j 2 XML configuration</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
  <Appenders>
    <File name="A1" fileName="A1.log" append="false">
      <PatternLayout pattern="%t %-5p %c{2} - %m%n"/>
    </File>
    <Console name="STDOUT" target="SYSTEM_OUT">
      <PatternLayout pattern="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Logger name="org.apache.log4j.xml" level="debug">
      <AppenderRef ref="A1"/>
    </Logger>
    <Root level="debug">
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>
</Configuration>]]></pre>

            <h4>Sample 3 - SocketAppender</h4>
            <p>Log4j 1.x XML configuration. This example from Log4j 1.x is misleading. The SocketAppender does not
              actually use a Layout. Configuring one will have no effect.</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration PUBLIC "-//APACHE//DTD LOG4J 1.2//EN" "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
  <appender name="A1" class="org.apache.log4j.net.SocketAppender">
    <param name="RemoteHost" value="localhost"/>
    <param name="Port" value="5000"/>
    <param name="LocationInfo" value="true"/>
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%t %-5p %c{2} - %m%n"/>
    </layout>
  </appender>
  <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </layout>
  </appender>
  <category name="org.apache.log4j.xml">
    <priority value="debug"/>
    <appender-ref ref="A1"/>
  </category>
  <root>
    <priority value="debug"/>
    <appender-ref ref="STDOUT"/>
  </Root>
</log4j:configuration>]]></pre>

           <p>Log4j 2 XML configuration</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
  <Appenders>
    <Socket name="A1" host="localHost" port="5000">
      <SerializedLayout/>
    </Socket>
    <Console name="STDOUT" target="SYSTEM_OUT">
      <PatternLayout pattern="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Logger name="org.apache.log4j.xml" level="debug">
      <AppenderRef ref="A1"/>
    </Logger>
    <Root level="debug">
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>
</Configuration>]]></pre>

            <h4>Sample 4 - AsyncAppender</h4>
            <p>Log4j 1.x XML configuration using the AsyncAppender.</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration PUBLIC "-//APACHE//DTD LOG4J 1.2//EN" "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" configDebug="true">
  <appender name="ASYNC" class="org.apache.log4j.AsyncAppender">
    <appender-ref ref="TEMP"/>
  </appender>
  <appender name="TEMP" class="org.apache.log4j.FileAppender">
    <param name="File" value="temp"/>
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </layout>
  </appender>
  <root>
    <priority value="debug"/>
    <appender-ref ref="ASYNC"/>
  </Root>
</log4j:configuration>]]></pre>

           <p>Log4j 2 XML configuration. </p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="debug">
  <Appenders>
    <File name="TEMP" fileName="temp">
      <PatternLayout pattern="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </File>
    <Async name="ASYNC">
      <AppenderRef ref="TEMP"/>
    </Async>
  </Appenders>
  <Loggers>
    <Root level="debug">
      <AppenderRef ref="ASYNC"/>
    </Root>
  </Loggers>
</Configuration>]]></pre>


            <h4>Sample 5 - AsyncAppender with Console and File</h4>
            <p>Log4j 1.x XML configuration using the AsyncAppender.</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration PUBLIC "-//APACHE//DTD LOG4J 1.2//EN" "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" configDebug="true">
  <appender name="ASYNC" class="org.apache.log4j.AsyncAppender">
    <appender-ref ref="TEMP"/>
    <appender-ref ref="CONSOLE"/>
  </appender>
  <appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </layout>
  </appender>
  <appender name="TEMP" class="org.apache.log4j.FileAppender">
    <param name="File" value="temp"/>
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </layout>
  </appender>
  <root>
    <priority value="debug"/>
    <appender-ref ref="ASYNC"/>
  </Root>
</log4j:configuration>]]></pre>

            <p>Log4j 2 XML configuration. Note that the Async Appender should be configured after the appenders it
              references. This will allow it to shutdown properly.</p>
            <pre class="prettyprint linenums"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="debug">
  <Appenders>
    <Console name="CONSOLE" target="SYSTEM_OUT">
      <PatternLayout pattern="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </Console>
    <File name="TEMP" fileName="temp">
      <PatternLayout pattern="%d %-5p [%t] %C{2} (%F:%L) - %m%n"/>
    </File>
    <Async name="ASYNC">
      <AppenderRef ref="TEMP"/>
      <AppenderRef ref="CONSOLE"/>
    </Async>
  </Appenders>
  <Loggers>
    <Root level="debug">
      <AppenderRef ref="ASYNC"/>
    </Root>
  </Loggers>
</Configuration>]]></pre>
          </subsection>
        </section>
    </body>
</document>
