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：
- 容器的启动：
engine.start() - 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();}[图片上传失败...(image-bc6c2d-1616772543941)]
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。
deployApps：解决host下多个利用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)host.addChild()：这时猜触发context实例核心内容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