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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>
Log4j 1.x has a XMLLayout which is different from the XmlLayout in Log4j 2, the log4j-1.2-api module
contains a <code>Log4j1XmlLayout</code> which produce output in the format as in Log4j 1.x.
The Log4j 1.x <code>SimpleLayout</code> can be emulated with PatternLayout "%level - %m%n".
The Log4j 1.x <code>TTCCLayout</code> can be emulated with PatternLayout "%r [%t] %p %c %notEmpty{%ndc }- %m%n".
</p>
<p>
Both <code>PatternLayout</code> and <code>EnhancedPatternLayout</code> in Log4j 1.x can be replaced with
<code>PatternLayout</code> in Log4j 2. The log4j-1.2-api module contains two pattern conversions "%ndc" and "%properties" which
can be used to emulate "%x" and "%X" in Log4j 1.x PatternLayout ("%x" and %X" in Log4j 2 have a slightly different format).
</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, XMLLayout and SimpleLayout</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.xml.XMLLayout" />
</appender>
<appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.SimpleLayout" />
</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">
<Log4j1XmlLayout />
</File>
<Console name="STDOUT" target="SYSTEM_OUT">
<PatternLayout pattern="%level - %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">
<PatternLayout pattern="%t %-5p %c{2} - %m%n"/>
</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 and TTCCLayout</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.TTCCLayout">
<param name="ThreadPrinting" value="true"/>
<param name="CategoryPrefixing" value="true"/>
<param name="ContextPrinting" value="true"/>
</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="%r [%t] %p %c %notEmpty{%ndc }- %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>