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<h1>Debug logging</h1>

<p>BTM ships with <a href="http://www.slf4j.org/">SLF4J</a> which is a logging facade much like Apache Commons Logging but it's safe to use in application servers unlike Commons Logging which suffers from complex classloader issues.</p>

<p>Much like Commons Logging, SLF4J can route the log requests to many different implementations including the two most common ones: <a href="http://java.sun.com/j2se/1.4.2/docs/api/java/util/logging/package-summary.html">JDK 1.4</a> and <a href="http://logging.apache.org/log4j/">Log4J</a>.</p>

<p>By default, BTM is shipped with slf4j-jdk14-1.5.8.jar which is the the <a href="http://jcp.org/aboutJava/communityprocess/review/jsr047/">JSR 047 logging API (aka JDK 1.4 logging)</a> wrapper. If you want to use another logger, simply delete the slf4j-jdk14-1.5.8.jar file and replace it with any one from this list:</p>

<ul>
	<li><a href="http://repo2.maven.org/maven2/org/slf4j/slf4j-jdk14/1.5.8/slf4j-jdk14-1.5.8.jar">slf4j-jdk14-1.5.8.jar</a> for JSR 047 logging.</li>
	<li><a href="http://repo2.maven.org/maven2/org/slf4j/slf4j-jdk14/1.5.8/slf4j-log4j12-1.5.8.jar">slf4j-log4j12-1.5.8.jar</a> for Apache Log4J 1.2.x.</li>
	<li><a href="http://repo2.maven.org/maven2/org/slf4j/slf4j-jdk14/1.5.8/slf4j-nop-1.5.8.jar">slf4j-nop-1.5.8.jar</a> for no logging (logs are silently dropped).</li>
	<li><a href="http://repo2.maven.org/maven2/org/slf4j/slf4j-jdk14/1.5.8/slf4j-simple-1.5.8.jar">slf4j-simple-1.5.8.jar</a> for simple <code>System.out</code> output.</li>
</ul>

<p>You will also need to put the <a href="http://repo2.maven.org/maven2/org/slf4j/slf4j-api/1.5.8/slf4j-api-1.5.8.jar">slf4j-api-1.5.8.jar</a> file in your classpath as well, no matter which one of the above jars you choose.</p>

<p>Those jars come from the 1.5.8 distribution of SLF4J.</p>

<h2>Mapped Diagnostic Context</h2>
<p><em>This feature appeared in BTM 1.3.3 and is not available in earlier versions.</em></p>

<p>If your logging implementation supports MDC (like <a href="http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/MDC.html">Log4J does</a> for instance) BTM will push the transaction's GTRID in the logger's MDC when a transaction is created.</p>

<p>The GTRID is pushed under the <strong><code>btm-gtrid</code></strong> name. You can make it appear in your Log4J logs by adding it to the <code>ConversionPattern</code>:</p>

<table class="wysiwyg-macro" data-macro-name="code" data-macro-default-parameter="xml" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6eG1sfQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
 &lt;appender name="FileAppender" class="org.apache.log4j.FileAppender">
    &lt;param name="File" value="SomeLogFile.txt"/>
    &lt;layout class="org.apache.log4j.PatternLayout">
        &lt;param name="ConversionPattern" value="%X{btm-gtrid} - %m%n"/>
    &lt;/layout>
 &lt;/appender>
</pre></td></tr></table>

<p>When using a different implementation than Log4J, please refer to your logger's documentation to understand how to make use of this feature.</p>