系统中有自己的Netty服务器，同时指定Dubbo用Netty，然后LoggingHandler就没法用了。下面的代码回导致我的Netty服务器无法使用Netty自带的日志体系。如果我强制自己的Netty服务器晚于Dubbo加载，那么Dubbo也是无法使用到DubboLogger的。
```
public class NettyHelper {

    public static void setNettyLoggerFactory() {
        InternalLoggerFactory factory = InternalLoggerFactory.getDefaultFactory();
        if (factory == null || !(factory instanceof DubboLoggerFactory)) {
            InternalLoggerFactory.setDefaultFactory(new DubboLoggerFactory());
        }
    }
```
# Added content in English. Help with Google Translate
System is TCP server using Netty4, and Dubbo is specified to use Netty4. When I add LoggingHandler to ChannelPipeline of my System, The log is not expected. 
Like this:
![image](https://user-images.githubusercontent.com/11850956/37442060-5a02eabc-283f-11e8-939a-68255f8912b2.png)

I tracked the code and found the Logger is `com.alibaba.dubbo.remoting.transport.netty4.logging.NettyHelper.DubboLogger` instead of `io.netty.util.internal.logging.Slf4JLogger`.  DubboLogger added other content arount the original log. The NeetyHelper replace the InternalLoggerFactory when Dubbo loading, like the code block above shows.
# By the way.
My system build by Spring Boot, use default logging framework which is Slf4j + Logback.
Dubbo's logger is not extend default logger, but replace it.
![image](https://user-images.githubusercontent.com/11850956/37442386-0585c494-2841-11e8-8f8f-354e7f226726.png)

import io.netty.buffer.PooledByteBufAllocator;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.util.concurrent.DefaultThreadFactory;
import java.util.concurrent.TimeUnit;
/**
 * NettyClient.
 */
public class NettyClient extends AbstractClient {
    private static final Logger logger = LoggerFactory.getLogger(NettyClient.class);
    private static final NioEventLoopGroup nioEventLoopGroup = new NioEventLoopGroup(Constants.DEFAULT_IO_THREADS, new DefaultThreadFactory("NettyClientWorker", true));
    private Bootstrap bootstrap;
    private volatile Channel channel; 
    public NettyClient(final URL url, final ChannelHandler handler) throws RemotingException {
        super(url, wrapChannelHandler(url, handler));
    }
    @Override
    protected void doOpen() throws Throwable {
        NettyHelper.setNettyLoggerFactory();
        final NettyClientHandler nettyClientHandler = new NettyClientHandler(getUrl(), this);
        bootstrap = new Bootstrap();
        bootstrap.group(nioEventLoopGroup)
                .option(ChannelOption.SO_KEEPALIVE, true)
                .option(ChannelOption.TCP_NODELAY, true)
                .option(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT)