@Override
    public void activateOptions() {
        if (fileName != null) {
            try {
                setFile(fileName, fileAppend, bufferedIO, bufferSize);
            }
            catch (java.io.IOException e) {
                LogLog.error("setFile(" + fileName + "," + fileAppend + ") call failed.", e);
            }
        }
        else {
            // LogLog.error("File option not set for appender ["+name+"].");
            LogLog.warn("File option not set for appender [" + name + "].");
            LogLog.warn("Are you using FileAppender instead of ConsoleAppender?");
        }
    }
If the value of <b>File</b> is not <code>null</code>, then
{@link #setFile} is called with the values of <b>File</b> and
<b>Append</b> properties.

@since 0.8.1
metamorphosis-client-extension/src/main/java/com/taobao/metamorphosis/client/extension/log4j/FileStreamAppender.java