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<#import "_features.html" as f>

<@f.scaffold title="@Log (and friends)" logline="Captain's Log, stardate 24435.7: &quot;What was that line again?&quot;">
	<@f.history>
		<p>
			The various <code>@Log</code> variants were added in lombok v0.10.
			<em>NEW in lombok 0.10: </em>You can annotate any class with a log annotation to let lombok generate a logger field.<br/>
			The logger is named <code>log</code> and the field's type depends on which logger you have selected.
		</p><p>
			<em>NEW in lombok v1.16.24: </em>Addition of google's FluentLogger (flogger).
		</p>
	</@f.history>

	<@f.overview>
		<p>
			You put the variant of <code>@Log</code> on your class (whichever one applies to the logging system you use); you then have a static final <code>log</code> field, initialized to the name of your class, which you can then use to write log statements.
		</p><p>
			There are several choices available:<br />
			<dl>
				<dt>
					<code>@CommonsLog</code>
				</dt><dd>
					Creates <code><span class="keyword">private&nbsp;static&nbsp;final&nbsp;</span><a href="https://commons.apache.org/logging/apidocs/org/apache/commons/logging/Log.html">org.apache.commons.logging.Log</a>&nbsp;<span class="staticfield">log</span>&nbsp;=&nbsp;<a href="https://commons.apache.org/logging/apidocs/org/apache/commons/logging/LogFactory.html#getLog(java.lang.Class)">org.apache.commons.logging.LogFactory.getLog</a>(LogExample.<span class="keyword">class</span>);</code>
				</dd><dt>
					<code>@Flogger</code>
				</dt><dd>
					Creates <code><span class="keyword">private&nbsp;static&nbsp;final&nbsp;</span><a href="https://google.github.io/flogger/">com.google.common.flogger.FluentLogger</a>&nbsp;<span class="staticfield">log</span>&nbsp;=&nbsp;com.google.common.flogger.FluentLogger.forEnclosingClass();</code>
				</dd><dt>
					<code>@JBossLog</code>
				</dt><dd>
					Creates <code><span class="keyword">private&nbsp;static&nbsp;final&nbsp;</span><a href="https://docs.jboss.org/jbosslogging/latest/org/jboss/logging/Logger.html">org.jboss.logging.Logger</a>&nbsp;<span class="staticfield">log</span>&nbsp;=&nbsp;<a href="https://docs.jboss.org/jbosslogging/latest/org/jboss/logging/Logger.html#getLogger(java.lang.Class)">org.jboss.logging.Logger.getLogger</a>(LogExample.<span class="keyword">class</span>);</code>
				</dd><dt>
					<code>@Log</code>
				</dt><dd>
					Creates <code><span class="keyword">private&nbsp;static&nbsp;final&nbsp;</span><a href="https://docs.oracle.com/javase/6/docs/api/java/util/logging/Logger.html">java.util.logging.Logger</a>&nbsp;<span class="staticfield">log</span>&nbsp;=&nbsp;<a href="https://docs.oracle.com/javase/6/docs/api/java/util/logging/Logger.html#getLogger(java.lang.String)">java.util.logging.Logger.getLogger</a>(LogExample.<span class="keyword">class</span>.getName());</code>
				</dd><dt>
					<code>@Log4j</code>
				</dt><dd>
					Creates <code><span class="keyword">private&nbsp;static&nbsp;final&nbsp;</span><a href="https://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/Logger.html">org.apache.log4j.Logger</a>&nbsp;<span class="staticfield">log</span>&nbsp;=&nbsp;<a href="https://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/Logger.html#getLogger(java.lang.Class)">org.apache.log4j.Logger.getLogger</a>(LogExample.<span class="keyword">class</span>);</code>
				</dd><dt>
					<code>@Log4j2</code>
				</dt><dd>
					Creates <code><span class="keyword">private&nbsp;static&nbsp;final&nbsp;</span><a href="https://logging.apache.org/log4j/2.0/log4j-api/apidocs/org/apache/logging/log4j/Logger.html">org.apache.logging.log4j.Logger</a>&nbsp;<span class="staticfield">log</span>&nbsp;=&nbsp;<a href="https://logging.apache.org/log4j/2.0/log4j-api/apidocs/org/apache/logging/log4j/LogManager.html#getLogger(java.lang.Class)">org.apache.logging.log4j.LogManager.getLogger</a>(LogExample.<span class="keyword">class</span>);</code>
				</dd><dt>
					<code>@Slf4j</code>
				</dt><dd>
					Creates <code><span class="keyword">private&nbsp;static&nbsp;final&nbsp;</span><a href="https://www.slf4j.org/api/org/slf4j/Logger.html">org.slf4j.Logger</a>&nbsp;<span class="staticfield">log</span>&nbsp;=&nbsp;<a href="https://www.slf4j.org/api/org/slf4j/LoggerFactory.html#getLogger(java.lang.Class)">org.slf4j.LoggerFactory.getLogger</a>(LogExample.<span class="keyword">class</span>);</code>
				</dd><dt>
					<code>@XSlf4j</code>
				</dt><dd>
					Creates <code><span class="keyword">private&nbsp;static&nbsp;final&nbsp;</span><a href="https://www.slf4j.org/api/org/slf4j/ext/XLogger.html">org.slf4j.ext.XLogger</a>&nbsp;<span class="staticfield">log</span>&nbsp;=&nbsp;<a href="https://www.slf4j.org/api/org/slf4j/ext/XLoggerFactory.html#getXLogger(java.lang.Class)">org.slf4j.ext.XLoggerFactory.getXLogger</a>(LogExample.<span class="keyword">class</span>);</code>
				</dd>
			</dl>
		</p><p>
			By default, the topic (or name) of the logger will be the class name of the class annotated with the <code>@Log</code> annotation. This can be customised by specifying the <code>topic</code> parameter. For example: <code>@XSlf4j(topic="reporting")</code>.
		</p>
	</@f.overview>

	<@f.snippets name="Log" />

	<@f.confKeys>
		<dt>
			<code>lombok.log.fieldName</code> = <em>an identifier</em> (default: <code>log</code>).
		</dt><dd>
			The generated logger fieldname is by default '<code>log</code>', but you can change it to a different name with this setting.
		</dd><dt>
			<code>lombok.log.fieldIsStatic</code> = [<code>true</code> | <code>false</code>] (default: true)
		</dt><dd>
			Normally the generated logger is a <code>static</code> field. By setting this key to <code>false</code>, the generated field will be an instance field instead.
		</dd><dt>
			<code>lombok.log.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of any of the various log annotations as a warning or error if configured.
		</dd><dt>
			<code>lombok.log.apacheCommons.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of <code>@lombok.extern.apachecommons.CommonsLog</code> as a warning or error if configured.
		</dd><dt>
			<code>lombok.log.flogger.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of <code>@lombok.extern.flogger.Flogger</code> as a warning or error if configured.
		</dd><dt>
			<code>lombok.log.jbosslog.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of <code>@lombok.extern.jbosslog.JBossLog</code> as a warning or error if configured.
		</dd><dt>
			<code>lombok.log.javaUtilLogging.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of <code>@lombok.extern.java.Log</code> as a warning or error if configured.
		</dd><dt>
			<code>lombok.log.log4j.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of <code>@lombok.extern.log4j.Log4j</code> as a warning or error if configured.
		</dd><dt>
			<code>lombok.log.log4j2.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of <code>@lombok.extern.log4j.Log4j2</code> as a warning or error if configured.
		</dd><dt>
			<code>lombok.log.slf4j.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of <code>@lombok.extern.slf4j.Slf4j</code> as a warning or error if configured.
		</dd><dt>
			<code>lombok.log.xslf4j.flagUsage</code> = [<code>warning</code> | <code>error</code>] (default: not set)
		</dt><dd>
			Lombok will flag any usage of <code>@lombok.extern.slf4j.XSlf4j</code> as a warning or error if configured.
		</dd>
	</@f.confKeys>

	<@f.smallPrint>
		<p>
			If a field called <code>log</code> already exists, a warning will be emitted and no code will be generated.
		</p><p>
			A future feature of lombok's diverse log annotations is to find calls to the logger field and, if the chosen logging framework supports it and the log level can be compile-time determined from the log call, guard it with an <code>if</code> statement. This way if the log statement ends up being ignored, the potentially expensive calculation of the log string is avoided entirely. This does mean that you should <em>NOT</em> put any side-effects in the expression that you log.
		</p>
	</@f.smallPrint>
</@f.scaffold>