[logback-user] Error counter appender

[Lukas Zapletal]

Hello,

I need to count number of error messages coming thru SLF4J into my app and
integrate this number with System.exit() call at the end of the program.

I have found that best solution would be to write an appender and dynamicaly
add it in the code of my application. I am configuring logging by calling
LoggerConfigurer (loading XML file) but I do not want to have my appender in
this configuration - I do want to configure it dynamically not allowing user
to modify XML and disable this error counter appender. But this does not
work - the new appender method append() is never called. I think there is a
problem with context or something. Here is the code:

public class Test {
	final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(Test.class);

	public void main(String[] args) {
           String fileName = "myfile.xml";
	    LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();

		try {
			JoranConfigurator configurator = new JoranConfigurator();
			configurator.setContext(lc);
			// the context was probably already configured by default configuration
			// rules
			lc.shutdownAndReset();
			configurator.doConfigure(fileName);

			ErrorCounterAppender errAppender = new ErrorCounterAppender();
			Logger root = LoggerFactory.getLogger(LoggerContext.ROOT_NAME);
			errAppender.setContext(lc);
			errAppender.start();
			((ch.qos.logback.classic.Logger) root).addAppender(errAppender);
			logger.error("TEST");
			logger.info("Number of errors: {}", errAppender.getErrorNumber()); //
prints 0
			System.exit(errAppender.getErrorNumber()); // returns 0 (instead of 1)

		} catch (Throwable t) {
			logger.warn("Cannot configure logger from location " + fileName, t);
		}
		StatusPrinter.print(lc);
	}

}

I think there must be some problem in the context or something. Or is there
any better solution of my problem? Here is my appender:

/**

 * Thread-safe implementation of error counter appender for LogBack.

 */

public class ErrorCounterAppender extends AppenderBase<LoggingEvent> {



	AtomicInteger errorCounter = new AtomicInteger(0);



	private Layout<LoggingEvent> layout;



	public ErrorCounterAppender() {

	}



	@Override

	public void setLayout(Layout<LoggingEvent> layout) {

		this.layout = layout;

	}



	public void resetErrorNumber() {

		errorCounter.set(0);

	}



	public int getErrorNumber() {

		return errorCounter.get();

	}



	@Override

	public void start() {

		if (this.layout == null) {

			addError("No layout set for the appender named [" + name + "].");

			return;

		}

		super.start();

	}



	@Override

	public void append(LoggingEvent event) {

		if (event == null)

			return;



		if (Level.ERROR == event.getLevel()) {

			errorCounter.incrementAndGet();

		}

	}

}



-----
--
Lukas Zapletal
http://lukas.zapletalovi.com
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