In a recent post log4j-user list a developer asked whether it was
possible for log4j to log differently depending on technical
partitions such as web-app as opposed to EJB.
The original discussion can be found at:
http://marc.theaimsgroup.com/?t=116179536800005&r=1&w=2
A kind soul, namely James Stauffer, suggested filtering based on
MDC.
Here is an example of how you would do it in logback.
------------------------------------------
package chapter5;
import org.slf4j.LoggerFactory;
import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.MDC;
import ch.qos.logback.classic.joran.JoranConfigurator;
import ch.qos.logback.core.joran.spi.JoranException;
import ch.qos.logback.core.util.StatusPrinter;
public class GoMDC {
public static void main(String[] args) {
Logger logger = (Logger) LoggerFactory
.getLogger(GoMDC.class);
LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
try {
JoranConfigurator configurator = new JoranConfigurator();
configurator.setContext(lc);
configurator.doConfigure("mdcFilter.xml");
} catch (JoranException je) {
StatusPrinter.print(lc);
}
logger.debug("I know me " + 0);
MDC.put("key", "val");
logger.debug("I know me " + 1);
StatusPrinter.print(lc);
}
------------------------------------------
Here the associated config file, "mdcFilter.xml".
<configuration>
<appender name="STDOUT"
class="ch.qos.logback.core.ConsoleAppender">
<layout class="ch.qos.logback.classic.PatternLayout">
<param name="Pattern"
value="%-4relative [%thread] %-5level %X{testKey} - %msg%n" />
</layout>
<filter class="ch.qos.logback.core.filter.EvaluatorFilter">
<Name>myFilter</Name>
<OnMatch>DENY</OnMatch>
<Evaluator class="ch.qos.logback.classic.boolex.JaninoEventEvaluator">
<Name>mdcEvaluator</Name>
<Expression>mdc!=null &&
"val".equals(mdc.get("key"))</Expression>
</Evaluator>
</filter>
</appender>
<root>
<level value="debug" />
<appender-ref ref="STDOUT" />
</root>
</configuration>
The above has been tested on logback version 0.5.
It will yield the following output.
0 [main] DEBUG - I know me 0
|-INFO in ch.qos.logback.classic.joran.action.ConfigurationAction -
Ignoring debug attribute.
|-INFO in ch.qos.logback.core.joran.action.AppenderAction - About to
instantiate appender of type [ch.qos.logback.core.ConsoleAppender]
|-INFO in ch.qos.logback.core.joran.action.AppenderAction - Naming appender
as [STDOUT]
|-INFO in ch.qos.logback.core.joran.action.NestedComponentIA - is dmmed
applicable for /configuration/appender/filter
|-INFO in ch.qos.logback.core.joran.action.NestedComponentIA - Pushing
component <filter> on top of the object stack.
|-INFO in ch.qos.logback.core.joran.action.NestedComponentIA - is dmmed
applicable for /configuration/appender/filter/Evaluator
|-INFO in ch.qos.logback.core.joran.action.NestedComponentIA - Pushing
component <Evaluator> on top of the object stack.
|-INFO in ch.qos.logback.core.joran.action.AppenderAction - Popping
appender named [STDOUT] from the object stack
|-INFO in ch.qos.logback.classic.joran.action.LevelAction - root level set
to DEBUG
|-INFO in ch.qos.logback.core.joran.action.AppenderRefAction - Attaching
appender named [STDOUT to Logger[root]
Note that the last log statement is suppressed, which is the whole
point of the exercise.
--
Ceki Gülcü
Logback: The reliable, generic, fast and flexible logging framework for Java.
http://logback.qos.ch
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