进入NioEndpoint类的bind()
/** * Initialize the endpoint. */ @Override public void bind() throws Exception { //使用nio方式监听端口 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()); } //设置非阻塞 serverSock.configureBlocking(true); //mimic APR behavior ...... //开启selectorPool selectorPool.open(); } start过程tomcat的start阶段与init阶段相似，都是逐层调用，稍有不同的是在于engine，host，context，wrapper的启动方式；
首先回到Bootstrap的main方法中，继续执行Catalina类的start()，在start()方法中调getServer().start();
调用LifecycleBase类的start()方法，在这个方法中调动StandardServer类实现的startInternal()，在这个类中继续调用service的star()方法，以此类推逐层start调用，直到调用engine的start()，我们看下engine的start()方法，在看下StandardEngine的类图:
StandardEngine的startInternal()调用ContainerBase的startInternal()
/** * Start this component and implement the requirements * of {@link org.apache.catalina.util.LifecycleBase#startInternal()}. * * @exception LifecycleException if this component detects a fatal error * that prevents this component from being used */ @Override protected synchronized void startInternal() throws LifecycleException { ...... // Start our child containers, if any Container children[] = findChildren(); List<Future<Void>> results = new ArrayList<>(); for (int i = 0; i < children.length; i++) { results.add(startStopExecutor.submit(new StartChild(children[i]))); } ...... }findChildren()的方法找到的是engine容器的子容器然后在new StartChild(children[i])中调用子类容器的start()；使用这种方式依次启动子容器