RabbitMQ 客户端源码系列 - Channel

ConnectionFactory factory = new ConnectionFactory();
// "guest"/"guest" by default, limited to localhost connections
factory.setUsername(userName);
factory.setPassword(password);
factory.setVirtualHost(virtualHost);
factory.setHost(hostName);
factory.setPort(portNumber);

Connection conn = factory.newConnection();
//本次重点分析内容
Channel channel = connection.createChannel();

byte[] messageBodyBytes = "Hello, world!".getBytes();
channel.basicPublish(EXCHANGE_NAME, routingKey, MessageProperties.PERSISTENT_TEXT_PLAIN, messageBodyBytes);
channel.close();
connection.close();

/** Public API - {@inheritDoc} */
    @Override
    public Channel createChannel() throws IOException {
        // 确认 connection 为打开的状态
        ensureIsOpen();
       // 管理channel
        ChannelManager cm = _channelManager;
        if (cm == null) return null;
        // 创建 channel 核心的方法
        Channel channel = cm.createChannel(this);
        // 用于暴露指标
        metricsCollector.newChannel(channel);
        return channel;
    }

public ChannelN createChannel(AMQConnection connection) throws IOException {
        ChannelN ch;
     // 该 monitor 主要监控 _channelMap 和 channelNumberAllocator
        synchronized (this.monitor) {
           // 获取 channel 分配的编号
            int channelNumber = channelNumberAllocator.allocate();
            if (channelNumber == -1) {
                return null;
            } else {
                // 新增新的 channel
                ch = addNewChannel(connection, channelNumber);
            }
        }
     // 将新增的 channel 打开
        ch.open(); // now that it's been safely added
        return ch;
    }

private ChannelN addNewChannel(AMQConnection connection, int channelNumber) {
     // 判重
        if (_channelMap.containsKey(channelNumber)) {
            // That number's already allocated! Can't do it
            // This should never happen unless something has gone
            // badly wrong with our implementation.
            throw new IllegalStateException("We have attempted to "
                    + "create a channel with a number that is already in "
                    + "use. This should never happen. "
                    + "Please report this as a bug.");
        }
     // 构建
        ChannelN ch = instantiateChannel(connection, channelNumber, this.workService);
     // 放入 _channelMap 统一管理
        _channelMap.put(ch.getChannelNumber(), ch);
        return ch;
    }
public ChannelN(AMQConnection connection, int channelNumber,
        ConsumerWorkService workService, MetricsCollector metricsCollector) {
        // AMQChannel 构造函数
        super(connection, channelNumber);
        // 构建 消费分配器
        this.dispatcher = new ConsumerDispatcher(connection, this, workService);
        this.metricsCollector = metricsCollector;
    }

public void open() throws IOException {
        // 对rabbitmq broker 发送Channel.Open，并等待broker返回 Channel.OpenOk
        exnWrappingRpc(new Channel.Open(UNSPECIFIED_OUT_OF_BAND));
    }
    

public AMQCommand exnWrappingRpc(Method m)
        throws IOException
    {
        try {
          // 针对该方法进行rpc调用
            return privateRpc(m);
        } catch (AlreadyClosedException ace) {
            // Do not wrap it since it means that connection/channel
            // was closed in some action in the past
            throw ace;
        } catch (ShutdownSignalException ex) {
            throw wrap(ex);
        }
    }
    
    
private AMQCommand privateRpc(Method m)
        throws IOException, ShutdownSignalException
    {
      // 用于 rpc调用过程中 阻塞等待
        SimpleBlockingRpcContinuation k = new SimpleBlockingRpcContinuation(m);
        rpc(m, k);
        
        // 不超时等待
        if(_rpcTimeout == NO_RPC_TIMEOUT) {
            return k.getReply();
        } else {
            try {
               // 超时等待
                return k.getReply(_rpcTimeout);
            } catch (TimeoutException e) {
                throw wrapTimeoutException(m, e);
            }
        }
    }