tomcat源码分析系列之启动---庐山真面目

     上回我们说到Http11Protocol,它的init 和start方法：

/*
     * NOTE: There is no maintenance of state or checking for valid transitions
     * within this class. It is expected that the connector will maintain state
     * and prevent invalid state transitions.
     */

    @Override
    public void init() throws Exception {
        if (getLog().isInfoEnabled())
            getLog().info(sm.getString("abstractProtocolHandler.init",
                    getName()));

        if (oname == null) {
            // Component not pre-registered so register it
            oname = createObjectName();
            if (oname != null) {
                Registry.getRegistry(null, null).registerComponent(this, oname,
                    null);
            }
        }

        if (this.domain != null) {
            try {
                tpOname = new ObjectName(domain + ":" +
                        "type=ThreadPool,name=" + getName());
                Registry.getRegistry(null, null).registerComponent(endpoint,
                        tpOname, null);
            } catch (Exception e) {
                getLog().error(sm.getString(
                        "abstractProtocolHandler.mbeanRegistrationFailed",
                        tpOname, getName()), e);
            }
            rgOname=new ObjectName(domain +
                    ":type=GlobalRequestProcessor,name=" + getName());
            Registry.getRegistry(null, null).registerComponent(
                    getHandler().getGlobal(), rgOname, null );
        }

        String endpointName = getName();
        endpoint.setName(endpointName.substring(1, endpointName.length()-1));

        try {
            endpoint.init();
        } catch (Exception ex) {
            getLog().error(sm.getString("abstractProtocolHandler.initError",
                    getName()), ex);
            throw ex;
        }
    }


    @Override
    public void start() throws Exception {
        if (getLog().isInfoEnabled())
            getLog().info(sm.getString("abstractProtocolHandler.start",
                    getName()));
        try {
            endpoint.start();
        } catch (Exception ex) {
            getLog().error(sm.getString("abstractProtocolHandler.startError",
                    getName()), ex);
            throw ex;
        }
    }

 2个逻辑主要都调用了endpoint的对应方法，endpoint是JIoEndpoint的实例，JIoEndpoint实现了一个简单的服务器模型：监听线程接收到一个socket连接就会启动一个工作线程来处理。这里面有我们期待已久的Socket出现了。JIoEndpoint实现了虚类AbstractEndpoint，上面提到的endpoint.init()和endpoint.start()都是AbstractEndpoint里的方法

 public final void init() throws Exception {
        if (bindOnInit) {
            bind();
            bindState = BindState.BOUND_ON_INIT;
        }
    }
    
    public final void start() throws Exception {
        if (bindState == BindState.UNBOUND) {
            bind();
            bindState = BindState.BOUND_ON_START;
        }
        startInternal();
    }

 我们看JIoEndpoint的bind方法：

public void bind() throws Exception {

        // Initialize thread count defaults for acceptor
        if (acceptorThreadCount == 0) {
            acceptorThreadCount = 1;
        }
        // Initialize maxConnections
        if (getMaxConnections() == 0) {
            // User hasn't set a value - use the default
            setMaxConnections(getMaxThreads());
        }

        if (serverSocketFactory == null) {
            if (isSSLEnabled()) {
                serverSocketFactory =
                    handler.getSslImplementation().getServerSocketFactory(this);
            } else {
                serverSocketFactory = new DefaultServerSocketFactory(this);
            }
        }

        if (serverSocket == null) {
            try {
                if (getAddress() == null) {
                    serverSocket = serverSocketFactory.createSocket(getPort(),
                            getBacklog());
                } else {
                    serverSocket = serverSocketFactory.createSocket(getPort(),
                            getBacklog(), getAddress());
                }
            } catch (BindException orig) {
                String msg;
                if (getAddress() == null)
                    msg = orig.getMessage() + " <null>:" + getPort();
                else
                    msg = orig.getMessage() + " " +
                            getAddress().toString() + ":" + getPort();
                BindException be = new BindException(msg);
                be.initCause(orig);
                throw be;
            }
        }
        
    }
    

 bind方法主要实例化了serverSocket，接着看startInternal方法

@Override
    public void startInternal() throws Exception {

        if (!running) {
            running = true;
            paused = false;

            // Create worker collection
            if (getExecutor() == null) {
                createExecutor();
            }
            
            initializeConnectionLatch();

            // Start acceptor threads
            for (int i = 0; i < acceptorThreadCount; i++) {
                Thread acceptorThread = new Thread(new Acceptor(),
                        getName() + "-Acceptor-" + i);
                acceptorThread.setPriority(threadPriority);
                acceptorThread.setDaemon(getDaemon());
                acceptorThread.start();
            }
            
            // Start async timeout thread
            Thread timeoutThread = new Thread(new AsyncTimeout(),
                    getName() + "-AsyncTimeout");
            timeoutThread.setPriority(threadPriority);
            timeoutThread.setDaemon(true);
            timeoutThread.start();
        }
    }
startInternal 首先创建了一个处理队列，
然后生成一个最大连接数限制对象LimitLatch，
生成一组接收线程，并启动所有线程。
生成一个后台线程用以检查超时请求。 
我们看Acceptor的run方法：
public void run() {

            int errorDelay = 0;

            // Loop until we receive a shutdown command
            while (running) {

                // Loop if endpoint is paused
                while (paused && running) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        // Ignore
                    }
                }

                if (!running) {
                    break;
                }
                try {
                    //if we have reached max connections, wait
                    countUpOrAwaitConnection();
                    
                    Socket socket = null;
                    try {
                        // Accept the next incoming connection from the server
                        // socket
                        socket = serverSocketFactory.acceptSocket(serverSocket);
                    } catch (IOException ioe) {
                        // Introduce delay if necessary
                        errorDelay = handleExceptionWithDelay(errorDelay);
                        // re-throw
                        throw ioe;
                    }
                    // Successful accept, reset the error delay
                    errorDelay = 0;

                    // Configure the socket
                    if (setSocketOptions(socket)) {
                        // Hand this socket off to an appropriate processor
                        if (!processSocket(socket)) {
                            // Close socket right away
                            try {
                                socket.close();
                            } catch (IOException e) {
                                // Ignore
                            }
                        }
                    } else {
                        // Close socket right away
                        try {
                            socket.close();
                        } catch (IOException e) {
                            // Ignore
                        }
                    }
                } catch (IOException x) {
                    if (running) {
                        log.error(sm.getString("endpoint.accept.fail"), x);
                    }
                } catch (NullPointerException npe) {
                    if (running) {
                        log.error(sm.getString("endpoint.accept.fail"), npe);
                    }
                } catch (Throwable t) {
                    ExceptionUtils.handleThrowable(t);
                    log.error(sm.getString("endpoint.accept.fail"), t);
                }
                // The processor will recycle itself when it finishes
            }
        }
    } 
这是一个典型的socket监听处理程序。目前我们不去追究里面太多的细节，先形成一个整体的形象上的认识，到目前
为止，监听真正的建立起来了，意味着tomcat可以接受、处理请求了。