Netty:options和configs

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在使用Netty时，初始化服务端或客户端时，我们经常会看到如下代码

Bootstrap b = new Bootstrap();
......
b.channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true);

private final Map<ChannelOption<?>, Object> options = new LinkedHashMap<ChannelOption<?>, Object>();

@SuppressWarnings("unchecked")
public <T> B option(ChannelOption<T> option, T value) {
	if (option == null) {
		throw new NullPointerException("option");
	}
	if (value == null) {
		synchronized (options) {
			options.remove(option);
		}
	} else {
		synchronized (options) {
			options.put(option, value);
		}
	}
	return (B) this;
}

ChannelOption有很多选项可以设置，具体可以参见Netty文档http://netty.io/4.1/api/io/netty/channel/ChannelOption.html

当我们要使用设置好的option时，其实是通过Channel的Config去访问的，那我们设置的option是怎样写入Config的呢？以NioSocketChannel为例，初始化时

public NioSocketChannel(Channel parent, SocketChannel socket) {
	super(parent, socket);
	config = new NioSocketChannelConfig(this, socket.socket());
}

@Override
@SuppressWarnings("unchecked")
void init(Channel channel) throws Exception {
	ChannelPipeline p = channel.pipeline();
	......
	final Map<ChannelOption<?>, Object> options = options();
	synchronized (options) {
		for (Entry<ChannelOption<?>, Object> e: options.entrySet()) {
			try {
				if (!channel.config().setOption((ChannelOption<Object>) e.getKey(), e.getValue())) {
					logger.warn("Unknown channel option: " + e);
				}
			} catch (Throwable t) {
				logger.warn("Failed to set a channel option: " + channel, t);
			}
		}
	}

	......
}

    @Override
    @SuppressWarnings("deprecation")
    public <T> boolean setOption(ChannelOption<T> option, T value) {
        validate(option, value);

        if (option == CONNECT_TIMEOUT_MILLIS) {
            setConnectTimeoutMillis((Integer) value);
        } else if (option == MAX_MESSAGES_PER_READ) {
            setMaxMessagesPerRead((Integer) value);
        } else if (option == WRITE_SPIN_COUNT) {
            setWriteSpinCount((Integer) value);
        } else if (option == ALLOCATOR) {
            setAllocator((ByteBufAllocator) value);
        } else if (option == RCVBUF_ALLOCATOR) {
            setRecvByteBufAllocator((RecvByteBufAllocator) value);
        } else if (option == AUTO_READ) {
            setAutoRead((Boolean) value);
        } else if (option == AUTO_CLOSE) {
            setAutoClose((Boolean) value);
        } else if (option == WRITE_BUFFER_HIGH_WATER_MARK) {
            setWriteBufferHighWaterMark((Integer) value);
        } else if (option == WRITE_BUFFER_LOW_WATER_MARK) {
            setWriteBufferLowWaterMark((Integer) value);
        } else if (option == MESSAGE_SIZE_ESTIMATOR) {
            setMessageSizeEstimator((MessageSizeEstimator) value);
        } else {
            return false;
        }

        return true;
    }

NioSocketChannelConfig的继承关系如下

NioSocketChannelConfig extends DefaultSocketChannelConfig extends DefaultChannelConfig implements ChannelConfig

    public <T> T getOption(ChannelOption<T> option) {
        if (option == null) {
            throw new NullPointerException("option");
        }

        if (option == CONNECT_TIMEOUT_MILLIS) {
            return (T) Integer.valueOf(getConnectTimeoutMillis());
        }
        ......
        return null;
    }

        public final void connect(
            ......
            try {
                ......
                boolean wasActive = isActive();
                if (doConnect(remoteAddress, localAddress)) {
                    fulfillConnectPromise(promise, wasActive);
                } else {
                    connectPromise = promise;
                    requestedRemoteAddress = remoteAddress;

                    // Schedule connect timeout.
                    int connectTimeoutMillis = config().getConnectTimeoutMillis();
                    if (connectTimeoutMillis > 0) {
                        connectTimeoutFuture = eventLoop().schedule(new OneTimeTask() {
                            @Override
                            public void run() {
                                ChannelPromise connectPromise = AbstractNioChannel.this.connectPromise;
                                ConnectTimeoutException cause =
                                        new ConnectTimeoutException("connection timed out: " + remoteAddress);
                                if (connectPromise != null && connectPromise.tryFailure(cause)) {
                                    close(voidPromise());
                                }
                            }
                        }, connectTimeoutMillis, TimeUnit.MILLISECONDS);
                    }
                    ......
                }
            } catch (Throwable t) {
                promise.tryFailure(annotateConnectException(t, remoteAddress));
                closeIfClosed();
            }
        }

Netty:options和configs

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原文地址：http://blog.csdn.net/bdmh/article/details/50051643