code: public boolean addWriter(String logService, LogWriter writer)
  	{
  		if (logService != null && logService.length() > 0) {
  			final LogService l = (LogService) loggers.get(logService);
  			if (l != null)
  				l.addWriter(writer);
  			return l != null;
  		}
  		synchronized (loggers) {
  			writers.add(writer);
  			for (final Iterator i = loggers.values().iterator(); i.hasNext();)
  				((LogService) i.next()).addWriter(writer);
  			return true;
  		}
  	}
docs: Adds a log writer, either global or to a particular log service.
  <p>
  Note that the writer is added to the log service(s) regardless if it was already
  added before.<br>
  If the writer is added global, it will receive logging information from all log
  services that are already registered or will be registered in the future.
  
  @param logService name of a log service; to add the writer global, use an empty
  string or <code>null</code>
  @param writer log writer to add
  @return true if the writer was added successfully,<br>
  false a specified log service name was not found
  @see LogService#addWriter(LogWriter)