Sample log4j.xml file to turn on logging for HTTPBuilder and Apache HttpClient. Place log4j.xml file in your groovy home /conf directory.

log4j.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="false">
	<appender name="console" class="org.apache.log4j.ConsoleAppender">
		<param name="Target" value="System.out" />
		<layout class="org.apache.log4j.PatternLayout">
			<param name="ConversionPattern" value="%d{ISO8601} %-5p  %c{1} - %m%n" />
		</layout>
	</appender>
	
	<category name="groovyx.net.http">
		<priority value="DEBUG" />
	</category>
	
	<!-- Use DEBUG to see basic request/response info;  
	     Use TRACE to see headers for HttpURLClient. -->
	<category name="groovyx.net.http.HttpURLClient">
		<priority value="TRACE" />
	</category>

	<category name="org.apache.http">
		<priority value="INFO" />
	</category>
	<category name="org.apache.http.headers">
		<priority value="DEBUG" />
	</category>
	<category name="org.apache.http.wire">
		<priority value="DEBUG" />
	</category>
	
	<root>
		<priority value="INFO" />
		<appender-ref ref="console" />
	</root>
</log4j:configuration>