Tomcat源码分析(十四) -- Endpoint

Tomcat 中的 AbstractEndpoint

AbstractEndpoint 的 init 方法

public void init() throws Exception {
    if (bindOnInit) {
        //调用 org.apache.tomcat.util.net.NioEndpoint 的bind方法
        //这个方法里面会打开 ServerSocketChannel 监听端口，到此整个 init 完成
        bind();
        bindState = BindState.BOUND_ON_INIT;
    }
    if (this.domain != null) {
        // Register endpoint (as ThreadPool - historical name)
        oname = new ObjectName(domain + ":type=ThreadPool,name=\"" + getName() + "\"");
        Registry.getRegistry(null, null).registerComponent(this, oname, null);

        ObjectName socketPropertiesOname = new ObjectName(domain +
                                                          ":type=ThreadPool,name=\"" + getName() + "\",subType=SocketProperties");
        socketProperties.setObjectName(socketPropertiesOname);
        Registry.getRegistry(null, null).registerComponent(socketProperties, socketPropertiesOname, null);

        for (SSLHostConfig sslHostConfig : findSslHostConfigs()) {
            registerJmx(sslHostConfig);
        }
    }
}

AbstractEndpoint 的 bind 方法

public void bind() throws Exception {
    //这里全是 NIO 方面的内容，Tomcat 中没有使用 Netty
    if (!getUseInheritedChannel()) {
        serverSock = ServerSocketChannel.open();
        socketProperties.setProperties(serverSock.socket());
        InetSocketAddress addr = (getAddress()!=null?new InetSocketAddress(getAddress(),getPort()):new InetSocketAddress(getPort()));
        serverSock.socket().bind(addr,getAcceptCount());
    } else {
        // 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"));
        }
    }
    serverSock.configureBlocking(true); //mimic APR behavior

    // Initialize thread count defaults for acceptor, poller
    if (acceptorThreadCount == 0) {
        // FIXME: Doesn't seem to work that well with multiple accept threads
        acceptorThreadCount = 1;
    }
    if (pollerThreadCount <= 0) {
        //minimum one poller thread
        pollerThreadCount = 1;
    }
    setStopLatch(new CountDownLatch(pollerThreadCount));

    // Initialize SSL if needed
    initialiseSsl();

    selectorPool.open();
}

AbstractEndpoint 的 start 方法

public final void start() throws Exception {
    //检查是否bind端口
    if (bindState == BindState.UNBOUND) {
        bind();
        bindState = BindState.BOUND_ON_START;
    }
    //核心在这里, 在 NioEndpoint 中实现
    startInternal();
}

NioEndpoint 的 startInternal 方法

public void startInternal() throws Exception {

    if (!running) {
        running = true;
        paused = false;
        //设置缓存
        processorCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                                                 socketProperties.getProcessorCache());
        eventCache = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                                             socketProperties.getEventCache());
        nioChannels = new SynchronizedStack<>(SynchronizedStack.DEFAULT_SIZE,
                                              socketProperties.getBufferPool());

        // Create worker collection
        //创建工作线程集合
        if ( getExecutor() == null ) {
            createExecutor();
        }

        initializeConnectionLatch();

        // Start poller threads
        //开启轮询线程
        pollers = new Poller[getPollerThreadCount()];
        for (int i=0; i<pollers.length; i++) {
            pollers[i] = new Poller();
            Thread pollerThread = new Thread(pollers[i], getName() + "-ClientPoller-"+i);
            pollerThread.setPriority(threadPriority);
            pollerThread.setDaemon(true);
            pollerThread.start();
        }
        //开启接收线程
        startAcceptorThreads();
    }
}

到此，整个 tomcat 的启动过程就结束了。后面接着讲如何处理一个请求

小结

• Endpoint 中使用了 NIO 监听接口