在上文揭开tomcat神秘的面纱之bootstrap初始化中，本菜鸟分析了bootstrap最终会经过初始化，加载，启动三个步骤。接着来分析加载过程。
加载过程如下：

tomcat的初始化过程.png

在加载过程中，实质是利用反射，调用catalina的load()方法.

//bootstrap.java
private void load(String[] arguments)
    throws Exception {
    String methodName = "load";
    //利用反射调用catalina的load方法 此处的catalinaDaemon为catalina
    Method method =
        catalinaDaemon.getClass().getMethod(methodName, paramTypes);
    method.invoke(catalinaDaemon, param);
}

在catalina加载过程中，会解析加载conf/server.xml文件，初始化server。

//catalina.java
 public void load() {
    initDirs();
    initNaming();
    Digester digester = createStartDigester();//创建解析器，degister解析xml文件使用
    InputSource inputSource = null;
    InputStream inputStream = null;
    File file = null;
    file = configFile();//文件为conf/server.xml
    inputStream = new FileInputStream(file);
    inputSource = new InputSource(file.toURI().toURL().toString());
    if (inputStream == null) {
        inputStream = getClass().getClassLoader()
            .getResourceAsStream(getConfigFile());
        inputSource = new InputSource
            (getClass().getClassLoader()
             .getResource(getConfigFile()).toString());
    }
    if (inputStream == null) {
        inputStream = getClass().getClassLoader()
                .getResourceAsStream("server-embed.xml");
        inputSource = new InputSource
        (getClass().getClassLoader()
                .getResource("server-embed.xml").toString());
    
    }
    if (inputStream == null || inputSource == null) {
        return;
    }
    inputSource.setByteStream(inputStream);
    digester.push(this);
    digester.parse(inputSource);//server初始化在这里
    getServer().setCatalina(this);//设置server的catalina
    getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
    getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());
    initStreams();
    getServer().init();//初始化server
}

而在server中初始化过程中，实则是调用调用StandardService的init();方法。

//StandardServer.java
//LifecycleBase.java
public final synchronized void init() throws LifecycleException {
    if (!state.equals(LifecycleState.NEW)) {
        invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
    }
    setStateInternal(LifecycleState.INITIALIZING, null, false);//INITIALIZING事件
    initInternal();//在这里初始化
    setStateInternal(LifecycleState.INITIALIZED, null, false);//初始化成功事件   
}

protected void initInternal() throws LifecycleException {
    super.initInternal();
    onameStringCache = register(new StringCache(), "type=StringCache");
    MBeanFactory factory = new MBeanFactory();
    factory.setContainer(this);
    onameMBeanFactory = register(factory, "type=MBeanFactory");
    globalNamingResources.init();
    if (getCatalina() != null) {//加载jar包资源
        ClassLoader cl = getCatalina().getParentClassLoader();
        while (cl != null && cl != ClassLoader.getSystemClassLoader()) {
            if (cl instanceof URLClassLoader) {
                URL[] urls = ((URLClassLoader) cl).getURLs();
                for (URL url : urls) {
                    if (url.getProtocol().equals("file")) {
                        File f = new File (url.toURI());
                        if (f.isFile() &&
                                f.getName().endsWith(".jar")) {
                            ExtensionValidator.addSystemResource(f);
                        }
                    }
                }
            }
            cl = cl.getParent();
        }
    }
    for (int i = 0; i < services.length; i++) {
        services[i].init();//调用StandardService 的init方法。
    }
}

而在StandardService的init();方法中，实质调用和server一样，都会调用initInternal() 方法，两者都继承与LifecycleBase接口，而在StandardService中，则是初始化了engine和connector，这两个配置都是在conf/server.xml中。

 @Override
//StandardService.java
protected void initInternal() throws LifecycleException {
    super.initInternal();
    if (engine != null) {
        engine.init();//初始化engine在这里
    }
    for (Executor executor : findExecutors()) {
        if (executor instanceof JmxEnabled) {
            ((JmxEnabled) executor).setDomain(getDomain());
        }
        executor.init();
    }
    mapperListener.init();
    synchronized (connectorsLock) {
        for (Connector connector : connectors) {
            connector.init();//初始化连接器
        }
    }
}

而在初始化connection的时候，实际是调用protocolHandler(AjpNio2Protocol)的init();方法，初始化 endPoint

protected void initInternal() throws LifecycleException {
    super.initInternal();
    if (protocolHandler == null) {
        throw new LifecycleException(
                sm.getString("coyoteConnector.protocolHandlerInstantiationFailed"));
    }
    adapter = new CoyoteAdapter(this);
    protocolHandler.setAdapter(adapter);
    if (null == parseBodyMethodsSet) {
        setParseBodyMethods(getParseBodyMethods());
    }
    if (protocolHandler.isAprRequired() && !AprLifecycleListener.isAprAvailable()) {
        throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoApr",
                getProtocolHandlerClassName()));
    }
    if (AprLifecycleListener.isAprAvailable() && AprLifecycleListener.getUseOpenSSL() &&
            protocolHandler instanceof AbstractHttp11JsseProtocol) {
        AbstractHttp11JsseProtocol<?> jsseProtocolHandler =
                (AbstractHttp11JsseProtocol<?>) protocolHandler;
        if (jsseProtocolHandler.isSSLEnabled() &&
                jsseProtocolHandler.getSslImplementationName() == null) {
            // OpenSSL is compatible with the JSSE configuration, so use it if APR is available
            jsseProtocolHandler.setSslImplementationName(OpenSSLImplementation.class.getName());
        }
    }
    protocolHandler.init();//实例AjpNio2Protocol,在这里初始化endPoint.
}

public void init() throws Exception {
    if (oname == null) {
        oname = createObjectName();
        if (oname != null) {
            Registry.getRegistry(null, null).registerComponent(this, oname, null);
        }
    }

    if (this.domain != null) {
        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));
    endpoint.setDomain(domain);
    endpoint.init();//初始化endPoint
}

而在endPoint初始化过程中，实则是打开了ServerSocketChannel，调用了Selector的open()方法。

//EndPoint.java
public final void init() throws Exception {
    if (bindOnInit) {
        bind();//在这里初始化ServerSocket
        bindState = BindState.BOUND_ON_INIT;
    }
    if (this.domain != null) {
        oname = new ObjectName(domain + ":type=ThreadPool,name=\"" + getName() + "\"");
        Registry.getRegistry(null, null).registerComponent(this, oname, null);

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

@Override
public void bind() throws Exception {
    initServerSocket();//初始化ServerSocket
    if (acceptorThreadCount == 0) {
        acceptorThreadCount = 1;
    }
    if (pollerThreadCount <= 0) {
        pollerThreadCount = 1;
    }
    setStopLatch(new CountDownLatch(pollerThreadCount));
    initialiseSsl();
    selectorPool.open();//selector.open();
}

  protected void initServerSocket() throws Exception {
    if (!getUseInheritedChannel()) {
        serverSock = ServerSocketChannel.open();//初始化ServerSocket
        socketProperties.setProperties(serverSock.socket());
        InetSocketAddress addr = (getAddress()!=null?new InetSocketAddress(getAddress(),getPort()):new InetSocketAddress(getPort()));
        serverSock.socket().bind(addr,getAcceptCount());
    } else {
        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); //设置非阻塞
}