Netty日志

netty的日志管理，优先使用slf4j，如果无法创建slf4j的log对象（可能是没有引用jar包），则使用log4j，再次会使用jdklog

    @SuppressWarnings("UnusedCatchParameter")
    private static InternalLoggerFactory newDefaultFactory(String name) {
        InternalLoggerFactory f;
        try {
            f = new Slf4JLoggerFactory(true);
            f.newInstance(name).debug("Using SLF4J as the default logging framework");
        } catch (Throwable t1) {
            try {
                f = new Log4JLoggerFactory();
                f.newInstance(name).debug("Using Log4J as the default logging framework");
            } catch (Throwable t2) {
                f = new JdkLoggerFactory();
                f.newInstance(name).debug("Using java.util.logging as the default logging framework");
            }
        }
        return f;
    }