关于java:Tomcat源码学习第3篇-Bootstrap的启动过程

上一篇咱们看了 Tomcat 中各个组件的 init 过程，初始化赋值好了，那么接下来就该轮到 start 了，话不多说，马上进入主题~

1. Bootstrap.start()

通过 start 办法咱们能够看到他是通过反射调用了 Catalina.start() 办法，按 F7 跳到这个类外面看一下。

public void start() throws Exception {if (catalinaDaemon == null) {init();
    }
    // 通过反射调用 Catalina.start() 办法
    Method method = catalinaDaemon.getClass().getMethod("start", (Class [])null);
    method.invoke(catalinaDaemon, (Object [])null);
}

2. Catalina.start()

进来一看，又是相熟的套娃格调，还得持续往里面跳转

3. LifecycleBase.start()

还是这个相熟的组件生命周期类，看到这里就好像看到了终局，必定是跟 initInternal 这个办法一样一层层嵌套进去，让咱们走起~

4. StandardServer.startInternal()

之前咱们有所过在一个 Tomcat 中是能够有多个 service 的，所以这里须要遍历所有的 service 别离让各自启动起来

在 server.xml 文件中再给他配置一个 <Service> 标签即可，如图所示：

5. StandardService.startInternal()

开始进入正题了，在这个办法中咱们能够看到它别离做了以下操作：

1. 容器的启动：engine.start()
2. 连接器的启动：connector.start()

protected void startInternal() throws LifecycleException {if(log.isInfoEnabled())
        log.info(sm.getString("standardService.start.name", this.name));
    setState(LifecycleState.STARTING);

    // 这里首先启动咱们定义的容器 engine
    if (engine != null) {synchronized (engine) {
            // 启动 engine 子容器
            engine.start();}
    }

    synchronized (executors) {for (Executor executor: executors) {executor.start();
        }
    }

    mapperListener.start();

    // Start our defined Connectors second
    synchronized (connectorsLock) {for (Connector connector: connectors) {
            try {
                // If it has already failed, don't try and start it
                if (connector.getState() != LifecycleState.FAILED) {
                    // 启动连接器
                    connector.start();}
            } catch (Exception e) {
                log.error(sm.getString(
                    "standardService.connector.startFailed",
                    connector), e);
            }
        }
    }
}

6. StandardEngine.startInternal()

这里间接调用的 ContainerBase.startInternal 办法实现上司组件的启动

protected synchronized void startInternal() throws LifecycleException {
    // Log our server identification information
    if(log.isInfoEnabled())
        log.info("Starting Servlet Engine:" + ServerInfo.getServerInfo());
    // Standard container startup
    super.startInternal();}

7. ContainerBase.startInternal()

这里应用的是线程池的形式，如果有多个 Host，那么就能够多个线程并行实例化Host，放慢Tomcat 启动速度

protected synchronized void startInternal() throws LifecycleException {
    // 启动上司容器
    logger = null;
    getLogger();
    Cluster cluster = getClusterInternal();
    if (cluster instanceof Lifecycle) {((Lifecycle) cluster).start();}
    Realm realm = getRealmInternal();
    if (realm instanceof Lifecycle) {((Lifecycle) realm).start();}

    // 查找并启动子容器，Host 在初始化阶段后还是不残缺的，须要持续封装，把容器关系保护残缺
    Container children[] = findChildren();
    List<Future<Void>> results = new ArrayList<>();
    for (Container child : children) {results.add(startStopExecutor.submit(new StartChild(child)));
    }

    MultiThrowable multiThrowable = null;

    for (Future<Void> result : results) {
        try {result.get();
        } catch (Throwable e) {log.error(sm.getString("containerBase.threadedStartFailed"), e);
            if (multiThrowable == null) {multiThrowable = new MultiThrowable();
            }
            multiThrowable.add(e);
        }

    }
    if (multiThrowable != null) {throw new LifecycleException(sm.getString("containerBase.threadedStartFailed"),
                                     multiThrowable.getThrowable());
    }

    // Start the Valves in our pipeline (including the basic), if any
    if (pipeline instanceof Lifecycle) {((Lifecycle) pipeline).start();}

    // 设置容器生命周期状态
    setState(LifecycleState.STARTING);

    // Start our thread
    threadStart();}

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8. StandardHost.startInternal()

protected synchronized void startInternal() throws LifecycleException {

    // Set error report valve
    String errorValve = getErrorReportValveClass();
    if ((errorValve != null) && (!errorValve.equals(""))) {
        try {
            boolean found = false;
            Valve[] valves = getPipeline().getValves();
            for (Valve valve : valves) {if (errorValve.equals(valve.getClass().getName())) {
                    found = true;
                    break;
                }
            }
            if(!found) {
                Valve valve =
                    (Valve) Class.forName(errorValve).getConstructor().newInstance();
                getPipeline().addValve(valve);
            }
        } catch (Throwable t) {ExceptionUtils.handleThrowable(t);
            log.error(sm.getString(
                    "standardHost.invalidErrorReportValveClass",
                    errorValve), t);
        }
    }
    super.startInternal();}

Host的实例化，是通过设置生命周期状态来进行促发生命周期事件 fireLifecycleEvent 来执行后续工作的。

1. deployApps：解决 host下多个利用
2. deployDirectories：解决 host 上面以目录形式部署的(results.add()，这里也是以多线程的形式并行执行的)
3. host.addChild()：这时猜触发 context 实例核心内容
4. context：具体读取 web.xml 封装 wrapper 过程应用事件驱动交给ContextConfig(它也是一个事件监听器)

9. MapperListener.startInternal()

public void startInternal() throws LifecycleException {setState(LifecycleState.STARTING);
        // 失去 engine 容器
        Engine engine = service.getContainer();
        if (engine == null) {return;}
        // 找到默认主机
        findDefaultHost();
        // 为以后容器以及子容器增加监听器
        addListeners(engine);
        // 注册 engine 下所有的 host
        Container[] conHosts = engine.findChildren();
        for (Container conHost : conHosts) {Host host = (Host) conHost;
            if (!LifecycleState.NEW.equals(host.getState())) {
                // 注册上下文和包装器
                registerHost(host);
            }
        }
    }

10. Connector.startInternal()

截至到这里，容器的注册与启动曾经实现了，接下来到连接器的启动了

protected void startInternal() throws LifecycleException {
    // Validate settings before starting
    if (getPort() < 0) {
        throw new LifecycleException(sm.getString("coyoteConnector.invalidPort", Integer.valueOf(getPort())));
    }

    setState(LifecycleState.STARTING);

    try {protocolHandler.start();
    } catch (Exception e) {
        throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerStartFailed"), e);
    }
}

11. AbstractProtocol.start()

这里对 EndPoint进行初始化

public void start() throws Exception {if (getLog().isInfoEnabled()) {getLog().info(sm.getString("abstractProtocolHandler.start", getName()));
    }

    endpoint.start();

    // Start timeout thread
    asyncTimeout = new AsyncTimeout();
    Thread timeoutThread = new Thread(asyncTimeout, getNameInternal() + "-AsyncTimeout");
    int priority = endpoint.getThreadPriority();
    if (priority < Thread.MIN_PRIORITY || priority > Thread.MAX_PRIORITY) {priority = Thread.NORM_PRIORITY;}
    timeoutThread.setPriority(priority);
    timeoutThread.setDaemon(true);
    timeoutThread.start();}

12. AbstractEndpoint.start()

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

13. NioEndpoint.bind()

public void bind() throws Exception {if (!getUseInheritedChannel()) {
        // 获取 nio 通道 channel
        serverSock = ServerSocketChannel.open();
        socketProperties.setProperties(serverSock.socket());
        InetSocketAddress addr = (getAddress()!=null?new InetSocketAddress(getAddress(),getPort()):new InetSocketAddress(getPort()));
        // 绑定端口，但尚未应用 accept 获取客户端连贯
        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();}

14. NioEndpoint.startInternal()

这里通过 startAcceptorThreads 启动 Accepter 线程，该线程用于接管新的 Socket 连贯

总结