Logback logs converter into GAE log (which uses JUL)

AppengineLogAppender

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Logger;

import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.spi.IThrowableProxy;
import ch.qos.logback.classic.spi.LoggingEvent;
import ch.qos.logback.classic.spi.StackTraceElementProxy;
import ch.qos.logback.core.AppenderBase;

public class AppEngineLogAppender<E> extends AppenderBase<E> {

	private static final Logger loggerUsedToLogIntoGAE = Logger.getLogger(AppEngineLogAppender.class.getName());
	
	@Override
	protected void append(E event) {

		LoggingEvent loggingEvent = (LoggingEvent) event;
		Level level = loggingEvent.getLevel();
		
		// Get the GAE logger associated with the Logback logger
		String loggerName = loggingEvent.getLoggerName();
		String logbackLogHandlerName = loggingEvent.getLoggerContextVO().getName();
		
		StringBuilder b = new StringBuilder();

		// Add the logged message into the final GAE logging message
		b.append(loggingEvent.getFormattedMessage().toString());

		// If we have to print a Stacktrace, we add it the end of the logging line
		IThrowableProxy throwableProxyFromLoggingEvent = loggingEvent.getThrowableProxy();
		if (throwableProxyFromLoggingEvent != null) {
			b.append("\n");
			
			// Write the first cause
			//   - Write the first line
			b.append(throwableProxyFromLoggingEvent.getClassName()).append(": ").append(throwableProxyFromLoggingEvent.getMessage()).append("\n");
			//   - Then the stacktrace lines with a tabulation
			for (StackTraceElementProxy line : throwableProxyFromLoggingEvent.getStackTraceElementProxyArray()) {
				b.append("\t").append(line.getSTEAsString()).append('\n');
			}
			b.append("\n");
			
			//   - Do the same for the Throwable cause
			IThrowableProxy newThrowableCause = throwableProxyFromLoggingEvent.getCause();
			while (newThrowableCause != null) {
				b.append(newThrowableCause.getClassName()).append(": ").append(newThrowableCause.getMessage()).append("\n");
				//   - Then the stacktrace lines with a tabulation
				for (StackTraceElementProxy line : newThrowableCause.getStackTraceElementProxyArray()) {
					b.append("\t").append(line.getSTEAsString()).append('\n');
				}
				b.append("\n");
				
				newThrowableCause = newThrowableCause.getCause();
			}
		}
		
		if (level.equals(Level.ERROR))
			logIntoGAEEmulatingLoggerName(java.util.logging.Level.SEVERE, b.toString(), loggerName, logbackLogHandlerName);
		else if (level.equals(Level.WARN))
			logIntoGAEEmulatingLoggerName(java.util.logging.Level.WARNING, b.toString(), loggerName, logbackLogHandlerName);
		else if (level.equals(Level.INFO))
			logIntoGAEEmulatingLoggerName(java.util.logging.Level.INFO, b.toString(), loggerName, logbackLogHandlerName);
		else if (level.equals(Level.DEBUG))
			logIntoGAEEmulatingLoggerName(java.util.logging.Level.FINE, b.toString(), loggerName, logbackLogHandlerName);
		else if (level.equals(Level.TRACE))
			logIntoGAEEmulatingLoggerName(java.util.logging.Level.FINEST, b.toString(), loggerName, logbackLogHandlerName);

	}

	private void logIntoGAEEmulatingLoggerName(java.util.logging.Level loggingLevel, String msg, String loggerName, String logbackLogHandlerName) {
		loggerUsedToLogIntoGAE.logp(loggingLevel, loggerName, logbackLogHandlerName, msg);
	}

}