When you use an XLogger and have the pattern layout configured to output class, line, or method it doesn't behave properly.

Using logback as the implementation it outputs a '?'
Using log4j it outputs 'LoggerWrapper'

Using slf4j 1.5.5, and logback 0.9.11 or log4j 1.2.15

To recreate:
public class Slf4JTest extends TestCase {

public void testLogging()

{ Logger logger = LoggerFactory.getLogger("TEST"); logger.debug("test logger"); XLogger xlogger = XLoggerFactory.getXLogger("TEST"); xlogger.debug("test logger"); }

}

LOG4j.properties:
log4j.rootLogger=WARN, CONSOLE
log4j.logger.TEST=DEBUG, CONSOLE
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d %-5p %C

{1}

:%L %M - %m%n

LOGBACK.xml:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
<layout class="ch.qos.logback.classic.PatternLayout">
<pattern>
%d

{ABSOLUTE}

%-5level %class

{36}

:%L %M - %msg%n
</pattern>
</layout>
</appender>
<logger name="TEST">
<level value="DEBUG" />
</logger>
<root>
<level value="WARN" />
<appender-ref ref="CONSOLE" />
</root>
</configuration>

Output from log4j:
2008-11-19 16:24:03,420 DEBUG Slf4JTest:14 testLogging - test Logger
2008-11-19 16:24:03,435 DEBUG LoggerWrapper:230 debug - test XLogger

Output from logback:
2008-11-19 16:28:44,969 DEBUG Slf4JTest:21 testLogging - test Logger
2008-11-19 16:28:45,015 DEBUG ?:? ? - test XLogger