ConnectorCreateRule
@Override
    public void begin(String namespace, String name, Attributes attributes)
            throws Exception {
        Service svc = (Service)digester.peek();
        Executor ex = null;
        if ( attributes.getValue("executor")!=null ) {
            ex = svc.getExecutor(attributes.getValue("executor"));
        }
        Connector con = new Connector(attributes.getValue("protocol"));
        if (ex != null) {
            setExecutor(con, ex);
        }
        String sslImplementationName = attributes.getValue("sslImplementationName");
        if (sslImplementationName != null) {
            setSSLImplementationName(con, sslImplementationName);
        }
        digester.push(con);
    }

public Connector(String protocol) {
        setProtocol(protocol);
        // Instantiate protocol handler
        ProtocolHandler p = null;
        try {
            Class<?> clazz = Class.forName(protocolHandlerClassName);
            // 反射調(diào)用ProtocolHandler的構(gòu)造方法的時(shí)候會(huì)做后續(xù)的初始化
            p = (ProtocolHandler) clazz.getConstructor().newInstance();
        } catch (Exception e) {
            log.error(sm.getString("coyoteConnector.protocolHandlerInstantiationFailed"), e);
        } finally {
            this.protocolHandler = p;
        }

public AbstractProtocol(AbstractEndpoint<S, ?> endpoint) {
        this.endpoint = endpoint;
        ConnectionHandler<S> cHandler = new ConnectionHandler<>(this);
        setHandler(cHandler);
        getEndpoint().setHandler(cHandler);
        setSoLinger(Constants.DEFAULT_CONNECTION_LINGER);
        setTcpNoDelay(Constants.DEFAULT_TCP_NO_DELAY);
    }

protected void initServerSocket() throws Exception {
        if (getUseInheritedChannel()) {
            // Retrieve the channel provided by the OS
            Channel ic = System.inheritedChannel();
            if (ic instanceof ServerSocketChannel) {
                serverSock = (ServerSocketChannel) ic;
            }
            if (serverSock == null) {
                throw new IllegalArgumentException(sm.getString("endpoint.init.bind.inherited"));
            }
        } else {
//    綁定服務(wù)端的傳輸層端口
            serverSock = ServerSocketChannel.open();
            socketProperties.setProperties(serverSock.socket());
            InetSocketAddress addr = new InetSocketAddress(getAddress(), getPortWithOffset());
            serverSock.socket().bind(addr,getAcceptCount());
        }
        serverSock.configureBlocking(true); //mimic APR behavior
    }

org.apache.tomcat.util.net.NioEndpoint#startInternal
public void startInternal() throws Exception {
        if (!running) {
            running = true;
            paused = false;
            if (socketProperties.getProcessorCache() != 0) {
                processorCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                        socketProperties.getProcessorCache());
            }
            if (socketProperties.getEventCache() != 0) {
                eventCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                        socketProperties.getEventCache());
            }
            if (socketProperties.getBufferPool() != 0) {
                nioChannels = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                        socketProperties.getBufferPool());
            }
            // Create worker collection
            if (getExecutor() == null) {
            //   創(chuàng)建Tomcat默認(rèn)線程池，未手動(dòng)配置  線程數(shù)10 - 200
                createExecutor();
            }
            // 這個(gè)是tomcat的連接數(shù)限制器
            initializeConnectionLatch();
            // Start poller thread
            poller = new Poller();
            Thread pollerThread = new Thread(poller, getName() + "-Poller");
            pollerThread.setPriority(threadPriority);
            pollerThread.setDaemon(true);
            pollerThread.start();
            startAcceptorThread();
        }
    }

public class Poller implements Runnable {
        private Selector selector;
        // PollerEvent          private NioSocketWrapper socketWrapper;   private int interestOps;
        // 向多路復(fù)用器注冊(cè)socket和需要處理的socket時(shí)間
        private final SynchronizedQueue<PollerEvent> events =
                new SynchronizedQueue<>();
            .........
        public Poller() throws IOException {
            this.selector = Selector.open();
        }
@Override
        public void run() {
            // Loop until destroy() is called
            while (true) {
                boolean hasEvents = false;
                try {
                    if (!close) {
                        hasEvents = events();
                        if (wakeupCounter.getAndSet(-1) > 0) {
                            // If we are here, means we have other stuff to do
                            // Do a non blocking select
                            keyCount = selector.selectNow();
                        } else {
                        // 默認(rèn)阻塞1秒鐘，監(jiān)聽需要交給線程池的處理任務(wù)
                            keyCount = selector.select(selectorTimeout);
                        }
                        wakeupCounter.set(0);
                    }
                    ...
                } catch (Throwable x) {
                    ExceptionUtils.handleThrowable(x);
                    log.error(sm.getString("endpoint.nio.selectorLoopError"), x);
                    continue;
                }
                Iterator<SelectionKey> iterator =
                    keyCount > 0 ? selector.selectedKeys().iterator() : null;
                // Walk through the collection of ready keys and dispatch
                // any active event.
                while (iterator != null && iterator.hasNext()) {
                    SelectionKey sk = iterator.next();
                    iterator.remove();
                    NioSocketWrapper socketWrapper = (NioSocketWrapper) sk.attachment();
                    // Attachment may be null if another thread has called
                    // cancelledKey()
                    if (socketWrapper != null) {
                        // 主角， 任務(wù)處理都在里面
                        processKey(sk, socketWrapper);
                    }
                }
                // Process timeouts
                timeout(keyCount,hasEvents);
            }
.............
        }

public class Acceptor<U> implements Runnable {
 @Override
    public void run() {
        int errorDelay = 0;
        long pauseStart = 0;
        try {
            // Loop until we receive a shutdown command
            while (!stopCalled) {
            ............
                if (stopCalled) {
                    break;
                }
                state = AcceptorState.RUNNING;
                try {
                    //if we have reached max connections, wait
                    endpoint.countUpOrAwaitConnection();
                    // Endpoint might have been paused while waiting for latch
                    // If that is the case, don't accept new connections
                    if (endpoint.isPaused()) {
                        continue;
                    }
                    U socket = null;
                    try {
                        // 等待新連接
                        socket = endpoint.serverSocketAccept();
                    } catch (Exception ioe) {
                        // We didn't get a socket
                        endpoint.countDownConnection();
                        if (endpoint.isRunning()) {
                            // Introduce delay if necessary
                            errorDelay = handleExceptionWithDelay(errorDelay);
                            // re-throw
                            throw ioe;
                        } else {
                            break;
                        }
                    }
                    // Successful accept, reset the error delay
                    errorDelay = 0;
                    // Configure the socket
                    if (!stopCalled && !endpoint.isPaused()) {
                        // 由endpoint來處理新連接、把新連接存在map里、向poller注冊(cè)PollerEndpoint
                        // 以后讀寫事件就由Poller交給線程池來管理
                        if (!endpoint.setSocketOptions(socket)) {
                            endpoint.closeSocket(socket);
                        }
                    } else {
                        endpoint.destroySocket(socket);
                    }
                }
                ........
        } finally {
            stopLatch.countDown();
        }
        state = AcceptorState.ENDED;
    }
}

@Override
    protected boolean setSocketOptions(SocketChannel socket) {
       .........
            NioSocketWrapper newWrapper = new NioSocketWrapper(channel, this);
            channel.reset(socket, newWrapper);
            connections.put(socket, newWrapper);
            socketWrapper = newWrapper;
            // Set socket properties
            // Disable blocking, polling will be used
            socket.configureBlocking(false);
          socketProperties.setProperties(socket.socket());
        // 注冊(cè)新連接
            poller.register(socketWrapper);
            return true;
        ...

public void register(final NioSocketWrapper socketWrapper) {
            socketWrapper.interestOps(SelectionKey.OP_READ);//this is what OP_REGISTER turns into.
            PollerEvent pollerEvent = createPollerEvent(socketWrapper, OP_REGISTER);
            addEvent(pollerEvent);
        }

public void run() {
            // Loop until destroy() is called
            while (true) {
                boolean hasEvents = false;
                try {
                    if (!close) {
                        hasEvents = events();
                        if (wakeupCounter.getAndSet(-1) > 0) {
                            // If we are here, means we have other stuff to do
                            // Do a non blocking select
                            keyCount = selector.selectNow();
                        } else {
                        // 默認(rèn)阻塞1秒鐘，監(jiān)聽需要交給線程池的處理任務(wù)
                            keyCount = selector.select(selectorTimeout);
                        }
                        wakeupCounter.set(0);
                    }
                    ...
                } catch (Throwable x) {
                    ExceptionUtils.handleThrowable(x);
                    log.error(sm.getString("endpoint.nio.selectorLoopError"), x);
                    continue;
                }
                Iterator<SelectionKey> iterator =
                    keyCount > 0 ? selector.selectedKeys().iterator() : null;
                // Walk through the collection of ready keys and dispatch
                // any active event.
                while (iterator != null && iterator.hasNext()) {
                    SelectionKey sk = iterator.next();
                    iterator.remove();
                    NioSocketWrapper socketWrapper = (NioSocketWrapper) sk.attachment();
                    // Attachment may be null if another thread has called
                    // cancelledKey()
                    if (socketWrapper != null) {
                        // 主角， 任務(wù)處理都在里面
                        processKey(sk, socketWrapper);
                    }
                }
                // Process timeouts
                timeout(keyCount,hasEvents);
            }
.............
        }

public void service(org.apache.coyote.Request req, org.apache.coyote.Response res) throws Exception {
        Request request = (Request) req.getNote(ADAPTER_NOTES);
        Response response = (Response) res.getNote(ADAPTER_NOTES);
        if (request == null) {
            // Create objects
            request = connector.createRequest();
            request.setCoyoteRequest(req);
            response = connector.createResponse();
            response.setCoyoteResponse(res);
            // 做兩種類型request的轉(zhuǎn)換
            request.setResponse(response);
            response.setRequest(request);
        }
        try {
            // Parse and set Catalina and configuration specific
            // 下面有講解這個(gè)方法
            postParseSuccess = postParseRequest(req, request, res, response);
            if (postParseSuccess) {
                // check valves if we support async
                request.setAsyncSupported(connector.getService().getContainer().getPipeline().isAsyncSupported());
                // Calling the container
               //把HttpServletRequest 和HttpServletRequest對(duì)象交給tomcat的職責(zé)鏈Pipeline。
connector.getService().getContainer().getPipeline().getFirst().invoke(request, response);
            }
            ........
    }

protected boolean postParseRequest(org.apache.coyote.Request req, Request request, org.apache.coyote.Response res,
            Response response) throws IOException, ServletException {
           // 解析出是否要Https
        if (req.scheme().isNull()) {
            // Use connector scheme and secure configuration, (defaults to
            // "http" and false respectively)
            req.scheme().setString(connector.getScheme());
            request.setSecure(connector.getSecure());
        } else {
            // Use processor specified scheme to determine secure state
            request.setSecure(req.scheme().equals("https"));
        }
// 代理相關(guān)
String proxyName = connector.getProxyName();
        int proxyPort = connector.getProxyPort();
        if (proxyPort != 0) {
            req.setServerPort(proxyPort);
        } else if (req.getServerPort() == -1) {
            // Not explicitly set. Use default ports based on the scheme
            if (req.scheme().equals("https")) {
                req.setServerPort(443);
            } else {
                req.setServerPort(80);
            }
        }
        if (proxyName != null) {
            req.serverName().setString(proxyName);
        }
// 預(yù)檢方法請(qǐng)求
// Check for ping OPTIONS * request
        if (undecodedURI.equals("*")) {
            if (req.method().equalsIgnoreCase("OPTIONS")) {
                StringBuilder allow = new StringBuilder();
                allow.append("GET, HEAD, POST, PUT, DELETE, OPTIONS");
                // Trace if allowed
                if (connector.getAllowTrace()) {
                    allow.append(", TRACE");
                }
                res.setHeader("Allow", allow.toString());
                // Access log entry as processing won't reach AccessLogValve
                connector.getService().getContainer().logAccess(request, response, 0, true);
                return false;
            } else {
                response.sendError(400, sm.getString("coyoteAdapter.invalidURI"));
            }
        }
        ........
 while (mapRequired) {
            // This will map the the latest version by default
          // tomcat可以部署多個(gè)應(yīng)用，找到具體在某個(gè)Context、Host、填充到request對(duì)象中。 
connector.getService().getMapper().map(serverName, decodedURI, version, request.getMappingData());
     }
.......

@Override
    public void invoke(Request request, Response response) throws IOException, ServletException {
        ...........
        // 獲取對(duì)應(yīng)servlet對(duì)應(yīng)的Wrapper， servlet可能還未加載
        StandardWrapper wrapper = (StandardWrapper) getContainer();
        Servlet servlet = null;
        Context context = (Context) wrapper.getParent();
        ........
        try {
            if (!unavailable) {
            // 獲取真正的servlet， 如果未加載初始化，在加載初始化后返回
                servlet = wrapper.allocate();
            }
        } catch (UnavailableException e) {
            container.getLogger().error(sm.getString("standardWrapper.allocateException", wrapper.getName()), e);
            checkWrapperAvailable(response, wrapper);
        } 
        .................
// ApplicationFilterChain本身是servlet規(guī)范中的過濾器， 持有servelt對(duì)象，使用職責(zé)鏈調(diào)用完成后，再調(diào)用servlet， 至此，tomcat的請(qǐng)求流程到此，后續(xù)交給上層應(yīng)用程序來處理請(qǐng)求
        ApplicationFilterChain filterChain = ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);
        .........
         filterChain.doFilter(request.getRequest(), response.getResponse());