@Override
    public void append(final LogEvent logEvent) {
        val refName = appenderRef.getRef();
        if (StringUtils.isNotBlank(refName)) {
            val appender = config.getAppender(refName);
            if (appender != null) {
                val newLogEvent = LoggingUtils.prepareLogEvent(logEvent);
                appender.append(newLogEvent);
                if (maxLogEntries > 0) {
                    if (logEvents.size() >= maxLogEntries) {
                        logEvents.poll();
                    }
                    logEvents.add(newLogEvent.toImmutable());
                }
            } else {
                LOGGER.warn("No log appender could be found for [{}]", refName);
            }
        } else {
            LOGGER.warn("No log appender reference for [{}] could be located in logging configuration.", refName);
        }
    }
Build cas appender.

@param name        the name
@param appenderRef the appender ref
@param filter      the filter
@param config      the config
@return the cas appender
core/cas-server-core-logging-api/src/main/java/org/apereo/cas/logging/CasAppender.java