Hello,

I would like to simplify stacktraces when errors occur in an application.  For example, with a hypothetical stack such as:

com.xyz.Wombat.doSomething
javax.servlet.http.HttpServlet.service
org.appserver.JspCompiler.handleJsp
org.appserver.ServletEngine.handleServlet
java.lang.Thread.run

...going down from top-to-bottom, I'd like to detect that line "org.appserver.JspCompiler.handleJsp" has been found, and exclude it -- and all subsequent "lower down" stack frames -- from logging output.

Looking at http://logback.qos.ch/manual/layouts.html#Evaluators I assume it must be possible with EventEvaluator because of the syntax %xEx{evaluator-n} but I can't find an example.  Furthermore, as I set up LogBack programmatically (and not via XML or any of bundled "configurator"), I'd be happiest if I could be directed towards an API-based example.

If it's of any use, here are two methods extracted from the class that I use to configure LogBack (incomplete but should help see what I'm trying to do, and how):

private synchronized boolean maybeInitialize(final Logger logger, String pattern)
{
// will throw ClassCastException if our configuration is incorrect (or accessed from wrong classloader)
// that's OK, it's what should happen...
final ch.qos.logback.classic.Logger impl = (ch.qos.logback.classic.Logger)logger;

// if there's an appender, then the logger seems to have been configured
Iterator<Appender<ILoggingEvent>> it = impl.iteratorForAppenders();
if (it.hasNext())
{
return false;
}

String logFileName = impl.getName();
if (logFileName.startsWith(LOG_FILE_STDPREFIX) && logFileName.length() > LOG_FILE_STDPREFIX.length())
{
logFileName = logFileName.substring(LOG_FILE_STDPREFIX.length());
}
logFileName += LOG_FILE_EXTENSION;

Appender<ILoggingEvent> appender;
if (CONFIG_VALUE_ROLL_TYPE_DATE.equals(_rollType))
{
appender = createRollByDateFileAppender(logFileName, pattern != null ? pattern : PATTERN_FOR_DATE);
}
else if (CONFIG_VALUE_ROLL_TYPE_SIZE.equals(_rollType))
{
appender = createRollBySizeFileAppender(logFileName, pattern);
}
else
{
appender = createFileAppender(logFileName, pattern);
}

appender.start();

impl.addAppender(appender);
impl.setLevel(_level);
impl.setAdditive(false);

return true;
}

private synchronized boolean maybeInitialize(final Logger logger, String pattern)
{
// will throw ClassCastException if our configuration is incorrect (or accessed from wrong classloader)
// that's OK, it's what should happen...
final ch.qos.logback.classic.Logger impl = (ch.qos.logback.classic.Logger)logger;

// if there's an appender, then the logger seems to have been configured
Iterator<Appender<ILoggingEvent>> it = impl.iteratorForAppenders();
if (it.hasNext())
{
return false;
}

String logFileName = impl.getName();
if (logFileName.startsWith(LOG_FILE_STDPREFIX) && logFileName.length() > LOG_FILE_STDPREFIX.length())
{
logFileName = logFileName.substring(LOG_FILE_STDPREFIX.length());
}
logFileName += LOG_FILE_EXTENSION;

Appender<ILoggingEvent> appender;
if (CONFIG_VALUE_ROLL_TYPE_DATE.equals(_rollType))
{
appender = createRollByDateFileAppender(logFileName, pattern != null ? pattern : PATTERN_FOR_DATE);
}
else if (CONFIG_VALUE_ROLL_TYPE_SIZE.equals(_rollType))
{
appender = createRollBySizeFileAppender(logFileName, pattern);
}
else
{
appender = createFileAppender(logFileName, pattern);
}

appender.start();

impl.addAppender(appender);
impl.setLevel(_level);
impl.setAdditive(false);

return true;
}


Thanks,
Christopher