Tomcat源码分析-加载和启动过程

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Tomcat启动过程

Tomcat启动类入口是org.apache.catalina.startup.Bootstrap类，里面有main方法，还有静态代码块，初始化运行环境变量：

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static {
    // 获取系统变量
    String userDir = System.getProperty("user.dir");

    
    String home = System.getProperty(Globals.CATALINA_HOME_PROP);
    File homeFile = null;
    // 获取安装目录
    if (home != null) {
        File f = new File(home);
        try {
            homeFile = f.getCanonicalFile();
        } catch (IOException ioe) {
            homeFile = f.getAbsoluteFile();
        }
    }

    if (homeFile == null) {
        // First fall-back. See if current directory is a bin directory
        // in a normal Tomcat install
        File bootstrapJar = new File(userDir, "bootstrap.jar");

        if (bootstrapJar.exists()) {
            File f = new File(userDir, "..");
            try {
                homeFile = f.getCanonicalFile();
            } catch (IOException ioe) {
                homeFile = f.getAbsoluteFile();
            }
        }
    }

    if (homeFile == null) {
        // Second fall-back. Use current directory
        File f = new File(userDir);
        try {
            homeFile = f.getCanonicalFile();
        } catch (IOException ioe) {
            homeFile = f.getAbsoluteFile();
        }
    }
    //设置安装目录
    catalinaHomeFile = homeFile;
    System.setProperty(
            Globals.CATALINA_HOME_PROP, catalinaHomeFile.getPath());

    // 设置工作目录
    String base = System.getProperty(Globals.CATALINA_BASE_PROP);
    if (base == null) {
        catalinaBaseFile = catalinaHomeFile;
    } else {
        File baseFile = new File(base);
        try {
            baseFile = baseFile.getCanonicalFile();
        } catch (IOException ioe) {
            baseFile = baseFile.getAbsoluteFile();
        }
        catalinaBaseFile = baseFile;
    }
    System.setProperty(
            Globals.CATALINA_BASE_PROP, catalinaBaseFile.getPath());
}

Main方法：

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public static void main(String args[]) {
    synchronized (daemonLock) {
        //创建主类 daemon是守护线程
        if (daemon == null) {
            // Don't set daemon until init() has completed
            //Bootstrap实例化
            Bootstrap bootstrap = new Bootstrap();
            try {
                bootstrap.init();
            } catch (Throwable t) {
                handleThrowable(t);
                t.printStackTrace();
                return;
            }
            daemon = bootstrap;
        } else {
            // When running as a service the call to stop will be on a new
            // thread so make sure the correct class loader is used to
            // prevent a range of class not found exceptions.
            Thread.currentThread().setContextClassLoader(daemon.catalinaLoader);
        }
    }

    try {
        String command = "start";
        if (args.length > 0) {
            command = args[args.length - 1];
        }

        if (command.equals("startd")) {
            args[args.length - 1] = "start";
            daemon.load(args);
            daemon.start();
        } else if (command.equals("stopd")) {
            args[args.length - 1] = "stop";
            daemon.stop();
        } else if (command.equals("start")) {
            daemon.setAwait(true);
            daemon.load(args);
            daemon.start();
            if (null == daemon.getServer()) {
                System.exit(1);
            }
        } else if (command.equals("stop")) {
            daemon.stopServer(args);
        } else if (command.equals("configtest")) {
            daemon.load(args);
            if (null == daemon.getServer()) {
                System.exit(1);
            }
            System.exit(0);
        } else {
            log.warn("Bootstrap: command \"" + command + "\" does not exist.");
        }
    } catch (Throwable t) {
        // Unwrap the Exception for clearer error reporting
        if (t instanceof InvocationTargetException &&
                t.getCause() != null) {
            t = t.getCause();
        }
        handleThrowable(t);
        t.printStackTrace();
        System.exit(1);
    }
}

初始化整个环境

bootstrap.init();

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public void init() throws Exception {
    //初始化类加载器
    initClassLoaders();
    //设置上下文加载器
    Thread.currentThread().setContextClassLoader(catalinaLoader);
    //设置安全加载器
    SecurityClassLoad.securityClassLoad(catalinaLoader);

    // Load our startup class and call its process() method
    if (log.isDebugEnabled())
        log.debug("Loading startup class");
    //反射的方式加载org.apache.catalina.startup.Catalina
    Class<?> startupClass = catalinaLoader.loadClass("org.apache.catalina.startup.Catalina");
    Object startupInstance = startupClass.getConstructor().newInstance();

    // 设置共享扩展类加载器
    if (log.isDebugEnabled())
        log.debug("Setting startup class properties");
    String methodName = "setParentClassLoader";
    Class<?> paramTypes[] = new Class[1];
    //设置父加载器
    paramTypes[0] = Class.forName("java.lang.ClassLoader");
    Object paramValues[] = new Object[1];
    paramValues[0] = sharedLoader;
    Method method =
        startupInstance.getClass().getMethod(methodName, paramTypes);
    method.invoke(startupInstance, paramValues);
    //把实例赋予catalinaDaemon
    catalinaDaemon = startupInstance;
}
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private void load(String[] arguments) throws Exception {

    // Call the load() method
    String methodName = "load";
    Object param[];
    Class<?> paramTypes[];
    if (arguments==null || arguments.length==0) {
        paramTypes = null;
        param = null;
    } else {
        paramTypes = new Class[1];
        paramTypes[0] = arguments.getClass();
        param = new Object[1];
        param[0] = arguments;
    }
    //反射执行了catalina的methodName（参数传过来）方法
    Method method =
        catalinaDaemon.getClass().getMethod(methodName, paramTypes);
    if (log.isDebugEnabled()) {
        log.debug("Calling startup class " + method);
    }
    method.invoke(catalinaDaemon, param);
}

/**
  * load新服务器信息
  */
public void load() {

    //看是否load过
    if (loaded) {
        return;
    }
    loaded = true;

    long t1 = System.nanoTime();
    //初始化目录
    initDirs();

    // Before digester - it may be needed
    //初始化命名空间
    initNaming();

    // 加载 解析 Server.xml文件，生成组件对象。
    Digester digester = createStartDigester();

    InputSource inputSource = null;
    InputStream inputStream = null;
    File file = null;
    try {
        try {
            file = configFile();
            inputStream = new FileInputStream(file);
            inputSource = new InputSource(file.toURI().toURL().toString());
        } catch (Exception e) {
            if (log.isDebugEnabled()) {
                log.debug(sm.getString("catalina.configFail", file), e);
            }
        }
        if (inputStream == null) {
            try {
                inputStream = getClass().getClassLoader()
                    .getResourceAsStream(getConfigFile());
                inputSource = new InputSource
                    (getClass().getClassLoader()
                      .getResource(getConfigFile()).toString());
            } catch (Exception e) {
                if (log.isDebugEnabled()) {
                    log.debug(sm.getString("catalina.configFail",
                            getConfigFile()), e);
                }
            }
        }

        // This should be included in catalina.jar
        // Alternative: don't bother with xml, just create it manually.
        if (inputStream == null) {
            try {
                inputStream = getClass().getClassLoader()
                        .getResourceAsStream("server-embed.xml");
                inputSource = new InputSource
                (getClass().getClassLoader()
                        .getResource("server-embed.xml").toString());
            } catch (Exception e) {
                if (log.isDebugEnabled()) {
                    log.debug(sm.getString("catalina.configFail",
                            "server-embed.xml"), e);
                }
            }
        }


        if (inputStream == null || inputSource == null) {
            if  (file == null) {
                log.warn(sm.getString("catalina.configFail",
                        getConfigFile() + "] or [server-embed.xml]"));
            } else {
                log.warn(sm.getString("catalina.configFail",
                        file.getAbsolutePath()));
                if (file.exists() && !file.canRead()) {
                    log.warn("Permissions incorrect, read permission is not allowed on the file.");
                }
            }
            return;
        }

        try {
            inputSource.setByteStream(inputStream);
            digester.push(this);
            digester.parse(inputSource);
        } catch (SAXParseException spe) {
            log.warn("Catalina.start using " + getConfigFile() + ": " +
                    spe.getMessage());
            return;
        } catch (Exception e) {
            log.warn("Catalina.start using " + getConfigFile() + ": " , e);
            return;
        }
    } finally {
        if (inputStream != null) {
            try {
                inputStream.close();
            } catch (IOException e) {
                // Ignore
            }
        }
    }
    //设置了工作目录和服务
    getServer().setCatalina(this);
    getServer().setCatalinaHome(Bootstrap.getCatalinaHomeFile());
    getServer().setCatalinaBase(Bootstrap.getCatalinaBaseFile());

    // Stream redirection
    initStreams();

    // Start the new server
    try {
        //初始化服务器
        getServer().init();
    } catch (LifecycleException e) {
        if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE")) {
            throw new java.lang.Error(e);
        } else {
            log.error("Catalina.start", e);
        }
    }

    long t2 = System.nanoTime();
    if(log.isInfoEnabled()) {
        log.info("Initialization processed in " + ((t2 - t1) / 1000000) + " ms");
    }
}

调用LifecyleBase方法初始化

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public final synchronized void init() throws LifecycleException {
    if (!state.equals(LifecycleState.NEW)) {
        invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
    }

    try {
        setStateInternal(LifecycleState.INITIALIZING, null, false);
        //真正的初始化容器方法
        initInternal();
        setStateInternal(LifecycleState.INITIALIZED, null, false);
    } catch (Throwable t) {
        handleSubClassException(t, "lifecycleBase.initFail", toString());
    }
}

initInternal();每个容器继承LifecycleMBeanBase。实现自己的初始化。

20200405112329

初始化各个容器组件

Server->Service->(Engine/Executor/Connector->ProtocolHandler->EndPoint->绑定协议)

这里没有一直初始化Context下去，到Engine就停止，后面的子容器都是在启动的时候初始化的。

初始化Server

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protected void initInternal() throws LifecycleException {

    super.initInternal();
    onameStringCache = register(new StringCache(), "type=StringCache");

    // Register the MBeanFactory 注册jMX 放到管理器
    MBeanFactory factory = new MBeanFactory();
    factory.setContainer(this);
    onameMBeanFactory = register(factory, "type=MBeanFactory");

    // Register the naming resources
    globalNamingResources.init();
    if (getCatalina() != null) {
        ClassLoader cl = getCatalina().getParentClassLoader();
        // Walk the class loader hierarchy. Stop at the system class loader.
        // This will add the shared (if present) and common class loaders
        while (cl != null && cl != ClassLoader.getSystemClassLoader()) {
            if (cl instanceof URLClassLoader) {
                URL[] urls = ((URLClassLoader) cl).getURLs();
                for (URL url : urls) {
                    if (url.getProtocol().equals("file")) {
                        try {
                            File f = new File (url.toURI());
                            if (f.isFile() &&
                                    f.getName().endsWith(".jar")) {
                                ExtensionValidator.addSystemResource(f);
                            }
                        } catch (URISyntaxException e) {
                            // Ignore
                        } catch (IOException e) {
                            // Ignore
                        }
                    }
                }
            }
            cl = cl.getParent();
        }
    }
    // 初始化我们定义的服务 可能有多个。
    for (int i = 0; i < services.length; i++) {
        services[i].init();
    }
}

这个方法又会初始化service

初始化Service

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@Override
protected void initInternal() throws LifecycleException {

    super.initInternal();

    //初始化 engine
    if (engine != null) {
        engine.init();
    }

    // Initialize any Executors 初始化线程池
    for (Executor executor : findExecutors()) {
        if (executor instanceof JmxEnabled) {
            ((JmxEnabled) executor).setDomain(getDomain());
        }
        executor.init();
    }

    // 初始化映射程序侦听器
    mapperListener.init();

    // Initialize our defined Connectors
    synchronized (connectorsLock) {
        for (Connector connector : connectors) {
            try {
                //初始化连接器
                connector.init();
            } catch (Exception e) {
                String message = sm.getString(
                        "standardService.connector.initFailed", connector);
                log.error(message, e);

                if (Boolean.getBoolean("org.apache.catalina.startup.EXIT_ON_INIT_FAILURE"))
                    throw new LifecycleException(message);
            }
        }
    }
}

初始化Service时，也会初始化线程池，Engine和Connector。

初始化Engine

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@Override
protected void initInternal() throws LifecycleException {
    // Ensure that a Realm is present before any attempt is made to start one. This will create the default NullRealm if necessary.
    getRealm();
    //这里个之前初始化容器不同，前面都是父容器初始化子容器，这里不同，不再初始化后面的容器，后面容器在启动中初始化。
    super.initInternal();
}

直接调用父类ContainerBase的方法

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@Override
protected void initInternal() throws LifecycleException {
    BlockingQueue<Runnable> startStopQueue = new LinkedBlockingQueue<>();
    startStopExecutor = new ThreadPoolExecutor(
            getStartStopThreadsInternal(),
            getStartStopThreadsInternal(), 10, TimeUnit.SECONDS,
            startStopQueue,
            new StartStopThreadFactory(getName() + "-startStop-"));
    startStopExecutor.allowCoreThreadTimeOut(true);
    super.initInternal();
}

初始化Connector

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//连接器初始化
@Override
protected void initInternal() throws LifecycleException {

    super.initInternal();

    // 初始化适配器
    adapter = new CoyoteAdapter(this);
    protocolHandler.setAdapter(adapter);

    // Make sure parseBodyMethodsSet has a default
    if (null == parseBodyMethodsSet) {
        setParseBodyMethods(getParseBodyMethods());
    }

    if (protocolHandler.isAprRequired() && !AprLifecycleListener.isInstanceCreated()) {
        throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprListener",
                getProtocolHandlerClassName()));
    }
    if (protocolHandler.isAprRequired() && !AprLifecycleListener.isAprAvailable()) {
        throw new LifecycleException(sm.getString("coyoteConnector.protocolHandlerNoAprLibrary",
                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());
        }
    }

    try {
        //protocolHandler初始化
        protocolHandler.init();
    } catch (Exception e) {
        throw new LifecycleException(
                sm.getString("coyoteConnector.protocolHandlerInitializationFailed"), e);
    }
}

这里同时初始化了适配器CoyoteAdapter和AbstractProtocol.ProtocolHandler

而ProtocolHandler又会初始化EndPoint监听器

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@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) {
        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);

    //监听器初始化 来监听protocolHandler
    endpoint.init();
}

后面就是绑定协议：

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public abstract void bind() throws Exception;
public abstract void unbind() throws Exception;
public abstract void startInternal() throws Exception;
public abstract void stopInternal() throws Exception;

public void init() throws Exception {
    if (bindOnInit) {
        bind();
        bindState = BindState.BOUND_ON_INIT;
    }
    if (this.domain != null) {
        // Register endpoint (as ThreadPool - historical name)
        oname = new ObjectName(domain + ":type=ThreadPool,name=\"" + getName() + "\"");
        Registry.getRegistry(null, null).registerComponent(this, oname, null);

        ObjectName socketPropertiesOname = new ObjectName(domain +
                ":type=ThreadPool,name=\"" + getName() + "\",subType=SocketProperties");
        socketProperties.setObjectName(socketPropertiesOname);
        Registry.getRegistry(null, null).registerComponent(socketProperties, socketPropertiesOname, null);

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

20200405112440

之后就是实例化ServerSocketl了。

启动服务

main方法中，启动daemon.start();其实是启动Catalina的start方法，之后启动服务：

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public void start() throws Exception {
    if (catalinaDaemon == null) {
        init();
    }
    //启动Catalina守护进程。
    Method method = catalinaDaemon.getClass().getMethod("start", (Class [])null);
    method.invoke(catalinaDaemon, (Object [])null);
}

//其实就是启动Catalina的start方法：
/**
  * Start a new server instance.
  * 启动服务器
  */
public void start() {

    if (getServer() == null) {
        load();
    }

    if (getServer() == null) {
        log.fatal("Cannot start server. Server instance is not configured.");
        return;
    }

    long t1 = System.nanoTime();

    // Start the new server
    try {
        getServer().start();
    } catch (LifecycleException e) {
        log.fatal(sm.getString("catalina.serverStartFail"), e);
        try {
            getServer().destroy();
        } catch (LifecycleException e1) {
            log.debug("destroy() failed for failed Server ", e1);
        }
        return;
    }

    long t2 = System.nanoTime();
    if(log.isInfoEnabled()) {
        log.info("Server startup in " + ((t2 - t1) / 1000000) + " ms");
    }

    // Register shutdown hook
    //为了安全关闭
    if (useShutdownHook) {
        if (shutdownHook == null) {
            shutdownHook = new CatalinaShutdownHook();
        }
        Runtime.getRuntime().addShutdownHook(shutdownHook);

        // If JULI is being used, disable JULI's shutdown hook since
        // shutdown hooks run in parallel and log messages may be lost
        // if JULI's hook completes before the CatalinaShutdownHook()
        LogManager logManager = LogManager.getLogManager();
        if (logManager instanceof ClassLoaderLogManager) {
            ((ClassLoaderLogManager) logManager).setUseShutdownHook(
                    false);
        }
    }

    if (await) {
        await();
        stop();
    }
}

服务启动，会调用LifecycleBean的start方法

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public final synchronized void start() throws LifecycleException {
    //启动后生命周期的不同状态，又有不同的操作。
    if (LifecycleState.STARTING_PREP.equals(state) || LifecycleState.STARTING.equals(state) ||
            LifecycleState.STARTED.equals(state)) {

        if (log.isDebugEnabled()) {
            Exception e = new LifecycleException();
            log.debug(sm.getString("lifecycleBase.alreadyStarted", toString()), e);
        } else if (log.isInfoEnabled()) {
            log.info(sm.getString("lifecycleBase.alreadyStarted", toString()));
        }

        return;
    }

    if (state.equals(LifecycleState.NEW)) {
        init();
    } else if (state.equals(LifecycleState.FAILED)) {
        stop();
    } else if (!state.equals(LifecycleState.INITIALIZED) &&
            !state.equals(LifecycleState.STOPPED)) {
        invalidTransition(Lifecycle.BEFORE_START_EVENT);
    }

    try {
        setStateInternal(LifecycleState.STARTING_PREP, null, false);
        //最终启动的方法。不同的实现，分别启动实现。
        startInternal();
        if (state.equals(LifecycleState.FAILED)) {
            // This is a 'controlled' failure. The component put itself into the
            // FAILED state so call stop() to complete the clean-up.
            stop();
        } else if (!state.equals(LifecycleState.STARTING)) {
            // Shouldn't be necessary but acts as a check that sub-classes are
            // doing what they are supposed to.
            invalidTransition(Lifecycle.AFTER_START_EVENT);
        } else {
            setStateInternal(LifecycleState.STARTED, null, false);
        }
    } catch (Throwable t) {
        // This is an 'uncontrolled' failure so put the component into the
        // FAILED state and throw an exception.
        handleSubClassException(t, "lifecycleBase.startFail", toString());
    }
}

启动子组件

启动server

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@Override
protected void startInternal() throws LifecycleException {
    //监听器做相应的处理
    fireLifecycleEvent(CONFIGURE_START_EVENT, null);
    //设置状态
    setState(LifecycleState.STARTING);

    globalNamingResources.start();

    // Start our defined Services
    synchronized (servicesLock) {
        for (int i = 0; i < services.length; i++) {
            services[i].start();
        }
    }
}

启动service

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protected void startInternal() throws LifecycleException {

    if(log.isInfoEnabled())
        log.info(sm.getString("standardService.start.name", this.name));
    setState(LifecycleState.STARTING);

    // engine启动
    if (engine != null) {
        synchronized (engine) {
            engine.start();
        }
    }

    //启动线程池
    synchronized (executors) {
        for (Executor executor: executors) {
            executor.start();
        }
    }

    //启动mapperListener监听器 主要用于处理映射关系
    mapperListener.start();

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

启动Engine

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@Override
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();
}

这里就不在启动子容器，而是执行父类方法。

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protected synchronized void startInternal() throws LifecycleException {

    // Start our subordinate components, if any
    logger = null;
    getLogger();
    //有集群启动集群
    Cluster cluster = getClusterInternal();
    if (cluster instanceof Lifecycle) {
        ((Lifecycle) cluster).start();
    }
    Realm realm = getRealmInternal();
    if (realm instanceof Lifecycle) {
        ((Lifecycle) realm).start();
    }

    // 启动子容器 使用Future同步执行
    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])));
    }

    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());
    }
    //直到所有的子组件启动完成

    // 启动我们管道中的阀门（包括基本阀门）pipeline
    if (pipeline instanceof Lifecycle) {
        ((Lifecycle) pipeline).start();
    }

    //设置生命周期
    setState(LifecycleState.STARTING);

    // Start our thread
    threadStart();
}

启动Connector

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public Connector(String protocol) {
    setProtocol(protocol);
    // 实例化协议处理程序
    ProtocolHandler p = null;
    try {
        //org.apache.coyote.http11.Http11NioProtocol
        Class<?> clazz = Class.forName(protocolHandlerClassName);
        p = (ProtocolHandler) clazz.getConstructor().newInstance();
    } catch (Exception e) {
        log.error(sm.getString(
                "coyoteConnector.protocolHandlerInstantiationFailed"), e);
    } finally {
        this.protocolHandler = p;
    }

    if (Globals.STRICT_SERVLET_COMPLIANCE) {
        uriCharset = StandardCharsets.ISO_8859_1;
    } else {
        uriCharset = StandardCharsets.UTF_8;
    }
}

连接器构造方法中实例化了一个ProtocolHandler协议处理器，用来处理请求。然后在启动方法中启动协议处理器。

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@Override
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);
    }
}

这些容器启动流程如下：
20200405225231

启动子容器

Host

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@Override
protected synchronized void startInternal() throws LifecycleException {

    // 错误处理
    String errorValve = getErrorReportValveClass();
    if ((errorValve != null) && (!errorValve.equals(""))) {
        try {
            boolean found = false;
            // Pipeline职责链
            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();
}

继续调用父类的startInternal

分层调用，子容器再掉父类startInternal，直到Context->Wrapper->没有子容器。结束

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//设置生命周期 后会激发监听器。
setState(LifecycleState.STARTING);

激活监听器后，回执行HostConfig中执行start

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public void start() {

    if (log.isDebugEnabled())
        log.debug(sm.getString("hostConfig.start"));

    //注册事件
    try {
        ObjectName hostON = host.getObjectName();
        oname = new ObjectName
            (hostON.getDomain() + ":type=Deployer,host=" + host.getName());
        Registry.getRegistry(null, null).registerComponent
            (this, oname, this.getClass().getName());
    } catch (Exception e) {
        log.warn(sm.getString("hostConfig.jmx.register", oname), e);
    }
    //主机处理
    if (!host.getAppBaseFile().isDirectory()) {
        log.error(sm.getString("hostConfig.appBase", host.getName(),
                host.getAppBaseFile().getPath()));
        host.setDeployOnStartup(false);
        host.setAutoDeploy(false);
    }

    //部署
    if (host.getDeployOnStartup())
        deployApps();

}

//为“应用程序根”目录中的任何目录或WAR文件部署应用程序。
protected void deployApps() {

    File appBase = host.getAppBaseFile();
    File configBase = host.getConfigBaseFile();
    String[] filteredAppPaths = filterAppPaths(appBase.list());
    //3中部署方式
    // 读取xml文件中Host <Context>
    deployDescriptors(configBase, configBase.list());
    // Deploy WARs
    deployWARs(appBase, filteredAppPaths);
    // Deploy expanded folders
    deployDirectories(appBase, filteredAppPaths);

}
//
protected void deployDirectories(File appBase, String[] files) {

    if (files == null)
        return;
    //启动一个线程池
    ExecutorService es = host.getStartStopExecutor();
    //运用同步的方式去部署。
    List<Future<?>> results = new ArrayList<>();

    for (int i = 0; i < files.length; i++) {

        if (files[i].equalsIgnoreCase("META-INF"))
            continue;
        if (files[i].equalsIgnoreCase("WEB-INF"))
            continue;
        File dir = new File(appBase, files[i]);
        if (dir.isDirectory()) {
            ContextName cn = new ContextName(files[i], false);

            if (isServiced(cn.getName()) || deploymentExists(cn.getName()))
                continue;

            results.add(es.submit(new DeployDirectory(this, cn, dir)));
        }
    }

    for (Future<?> result : results) {
        try {
            result.get();
        } catch (Exception e) {
            log.error(sm.getString(
                    "hostConfig.deployDir.threaded.error"), e);
        }
    }
}

//使用一个内部类来部署应用程序
private static class DeployDirectory implements Runnable {

    private HostConfig config;
    private ContextName cn;
    private File dir;

    public DeployDirectory(HostConfig config, ContextName cn, File dir) {
        this.config = config;
        this.cn = cn;
        this.dir = dir;
    }

    @Override
    public void run() {
        config.deployDirectory(cn, dir);
    }
}

//部署启动应用
protected void deployDirectory(ContextName cn, File dir) {
    long startTime = 0;
    // Deploy the application in this directory
    if( log.isInfoEnabled() ) {
        startTime = System.currentTimeMillis();
        log.info(sm.getString("hostConfig.deployDir",
                dir.getAbsolutePath()));
    }

    Context context = null;
    File xml = new File(dir, Constants.ApplicationContextXml);
    File xmlCopy =
            new File(host.getConfigBaseFile(), cn.getBaseName() + ".xml");


    DeployedApplication deployedApp;
    boolean copyThisXml = isCopyXML();
    boolean deployThisXML = isDeployThisXML(dir, cn);
    //拿到Context 开始部署。
    try {
        //实例化StandardContext
        if (deployThisXML && xml.exists()) {
            ///解析这个context节点  就是解析xml
            synchronized (digesterLock) {
                try {
                    context = (Context) digester.parse(xml);
                } catch (Exception e) {
                    log.error(sm.getString(
                            "hostConfig.deployDescriptor.error",
                            xml), e);
                    context = new FailedContext();
                } finally {
                    digester.reset();
                    if (context == null) {
                        context = new FailedContext();
                    }
                }
            }

            if (copyThisXml == false && context instanceof StandardContext) {
                // Host is using default value. Context may override it.
                copyThisXml = ((StandardContext) context).getCopyXML();
            }

            if (copyThisXml) {
                Files.copy(xml.toPath(), xmlCopy.toPath());
                context.setConfigFile(xmlCopy.toURI().toURL());
            } else {
                context.setConfigFile(xml.toURI().toURL());
            }
        } else if (!deployThisXML && xml.exists()) {
            // Block deployment as META-INF/context.xml may contain security
            // configuration necessary for a secure deployment.
            log.error(sm.getString("hostConfig.deployDescriptor.blocked",
                    cn.getPath(), xml, xmlCopy));
            context = new FailedContext();
        } else {
            context = (Context) Class.forName(contextClass).getConstructor().newInstance();
        }

        Class<?> clazz = Class.forName(host.getConfigClass());
        LifecycleListener listener = (LifecycleListener) clazz.getConstructor().newInstance();
        context.addLifecycleListener(listener);

        context.setName(cn.getName());
        context.setPath(cn.getPath());
        context.setWebappVersion(cn.getVersion());
        context.setDocBase(cn.getBaseName());
        //解析完成添加到Host中，进而把Context启动
        host.addChild(context);
    } catch (Throwable t) {
        ExceptionUtils.handleThrowable(t);
        log.error(sm.getString("hostConfig.deployDir.error",
                dir.getAbsolutePath()), t);
    } finally {
        deployedApp = new DeployedApplication(cn.getName(),
                xml.exists() && deployThisXML && copyThisXml);

        // Fake re-deploy resource to detect if a WAR is added at a later
        // point
        deployedApp.redeployResources.put(dir.getAbsolutePath() + ".war",
                Long.valueOf(0));
        deployedApp.redeployResources.put(dir.getAbsolutePath(),
                Long.valueOf(dir.lastModified()));
        if (deployThisXML && xml.exists()) {
            if (copyThisXml) {
                deployedApp.redeployResources.put(
                        xmlCopy.getAbsolutePath(),
                        Long.valueOf(xmlCopy.lastModified()));
            } else {
                deployedApp.redeployResources.put(
                        xml.getAbsolutePath(),
                        Long.valueOf(xml.lastModified()));
                // Fake re-deploy resource to detect if a context.xml file is
                // added at a later point
                deployedApp.redeployResources.put(
                        xmlCopy.getAbsolutePath(),
                        Long.valueOf(0));
            }
        } else {
            // Fake re-deploy resource to detect if a context.xml file is
            // added at a later point
            deployedApp.redeployResources.put(
                    xmlCopy.getAbsolutePath(),
                    Long.valueOf(0));
            if (!xml.exists()) {
                deployedApp.redeployResources.put(
                        xml.getAbsolutePath(),
                        Long.valueOf(0));
            }
        }
        addWatchedResources(deployedApp, dir.getAbsolutePath(), context);
        // Add the global redeploy resources (which are never deleted) at
        // the end so they don't interfere with the deletion process
        addGlobalRedeployResources(deployedApp);
    }

    deployed.put(cn.getName(), deployedApp);

    if( log.isInfoEnabled() ) {
        log.info(sm.getString("hostConfig.deployDir.finished",
                dir.getAbsolutePath(), Long.valueOf(System.currentTimeMillis() - startTime)));
    }
}

Context

前面context部署完成后启动,StandardContext类中的启动方法：

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@Override
protected synchronized void startInternal() throws LifecycleException {

    if(log.isDebugEnabled())
        log.debug("Starting " + getBaseName());

    // Send j2ee.state.starting notification
    //发布启动状态
    if (this.getObjectName() != null) {
        Notification notification = new Notification("j2ee.state.starting",
                this.getObjectName(), sequenceNumber.getAndIncrement());
        broadcaster.sendNotification(notification);
    }

    setConfigured(false);
    boolean ok = true;

    // Currently this is effectively a NO-OP but needs to be called to ensure the NamingResources follows the correct lifecycle
    //启动命名空间资源
    if (namingResources != null) {
        namingResources.start();
    }

    // Post work directory 工作目录
    postWorkDirectory();

    // 添加资源组件
    /**
     * 资源有4种:
     * Context.xml中的 <PrePresource></PrePresource>
     * WEB-INF/lib
     * Jar:<JarResource></JarResource>
     * post:<PostResource></PostResource>
     */
    if (getResources() == null) {   // (1) Required by Loader
        if (log.isDebugEnabled())
            log.debug("Configuring default Resources");

        try {
            setResources(new StandardRoot(this));
        } catch (IllegalArgumentException e) {
            log.error(sm.getString("standardContext.resourcesInit"), e);
            ok = false;
        }
    }
    if (ok) {
        //启动资源
        resourcesStart();
    }

    //加载webapp 加载器 父类是shareClassLoader
    if (getLoader() == null) {
        WebappLoader webappLoader = new WebappLoader();
        webappLoader.setDelegate(getDelegate());
        setLoader(webappLoader);
    }

    // An explicit cookie processor hasn't been specified; use the default
    if (cookieProcessor == null) {
        //初始化cookie
        cookieProcessor = new Rfc6265CookieProcessor();
    }

    // 初始化字符集映射器
    getCharsetMapper();

    // Validate required extensions
    boolean dependencyCheck = true;
    try {
        dependencyCheck = ExtensionValidator.validateApplication
            (getResources(), this);
    } catch (IOException ioe) {
        log.error(sm.getString("standardContext.extensionValidationError"), ioe);
        dependencyCheck = false;
    }

    //检查依赖
    if (!dependencyCheck) {
        // do not make application available if dependency check fails
        ok = false;
    }

    // 读取“catalina.useNaming”环境变量
    String useNamingProperty = System.getProperty("catalina.useNaming");
    if ((useNamingProperty != null)
        && (useNamingProperty.equals("false"))) {
        useNaming = false;
    }

    if (ok && isUseNaming()) {
        if (getNamingContextListener() == null) {
            NamingContextListener ncl = new NamingContextListener();
            ncl.setName(getNamingContextName());
            ncl.setExceptionOnFailedWrite(getJndiExceptionOnFailedWrite());
            addLifecycleListener(ncl);
            setNamingContextListener(ncl);
        }
    }

    // 标准容器启动
    if (log.isDebugEnabled())
        log.debug("Processing standard container startup");


    // Binding thread
    ClassLoader oldCCL = bindThread();

    try {
        if (ok) {
            // 启动我们的下属组件（如果有）
            Loader loader = getLoader();
            if (loader instanceof Lifecycle) {
                ((Lifecycle) loader).start();
            }

            // since the loader just started, the webapp classloader is now
            // created.
            //类加载器属性设置
            setClassLoaderProperty("clearReferencesRmiTargets",
                    getClearReferencesRmiTargets());
            setClassLoaderProperty("clearReferencesStopThreads",
                    getClearReferencesStopThreads());
            setClassLoaderProperty("clearReferencesStopTimerThreads",
                    getClearReferencesStopTimerThreads());
            setClassLoaderProperty("clearReferencesHttpClientKeepAliveThread",
                    getClearReferencesHttpClientKeepAliveThread());
            setClassLoaderProperty("clearReferencesObjectStreamClassCaches",
                    getClearReferencesObjectStreamClassCaches());
            setClassLoaderProperty("clearReferencesThreadLocals",
                    getClearReferencesThreadLocals());

            // By calling unbindThread and bindThread in a row, we setup the
            // current Thread CCL to be the webapp classloader
            unbindThread(oldCCL);
            oldCCL = bindThread();

            // Initialize logger again. Other components might have used it too early, so it should be reset.
            logger = null;
            getLogger();
            //域设置
            Realm realm = getRealmInternal();
            if(null != realm) {
                if (realm instanceof Lifecycle) {
                    ((Lifecycle) realm).start();
                }

                // Place the CredentialHandler into the ServletContext so
                // applications can have access to it. Wrap it in a "safe"
                // handler so application's can't modify it.
                CredentialHandler safeHandler = new CredentialHandler() {
                    @Override
                    public boolean matches(String inputCredentials, String storedCredentials) {
                        return getRealmInternal().getCredentialHandler().matches(inputCredentials, storedCredentials);
                    }

                    @Override
                    public String mutate(String inputCredentials) {
                        return getRealmInternal().getCredentialHandler().mutate(inputCredentials);
                    }
                };
                context.setAttribute(Globals.CREDENTIAL_HANDLER, safeHandler);
            }

            // 发送一个生命周期事件，之后，ContextConfig就会启动了  和之前Host套路一致,,调用ContextConfig的webConfig方法
            fireLifecycleEvent(Lifecycle.CONFIGURE_START_EVENT, null);

            // 启动子容器
            for (Container child : findChildren()) {
                if (!child.getState().isAvailable()) {
                    child.start();
                }
            }

            // 启动我们管道中的阀门（包括基本阀门），
            if (pipeline instanceof Lifecycle) {
                ((Lifecycle) pipeline).start();
            }

            // 获取群集管理器
            Manager contextManager = null;
            Manager manager = getManager();
            if (manager == null) {
                if (log.isDebugEnabled()) {
                    log.debug(sm.getString("standardContext.cluster.noManager",
                            Boolean.valueOf((getCluster() != null)),
                            Boolean.valueOf(distributable)));
                }
                if ((getCluster() != null) && distributable) {
                    try {
                        contextManager = getCluster().createManager(getName());
                    } catch (Exception ex) {
                        log.error("standardContext.clusterFail", ex);
                        ok = false;
                    }
                } else {
                    contextManager = new StandardManager();
                }
            }

            // Configure default manager if none was specified
            if (contextManager != null) {
                if (log.isDebugEnabled()) {
                    log.debug(sm.getString("standardContext.manager",
                            contextManager.getClass().getName()));
                }
                setManager(contextManager);
            }

            if (manager!=null && (getCluster() != null) && distributable) {
                //let the cluster know that there is a context that is distributable
                //and that it has its own manager
                getCluster().registerManager(manager);
            }
        }

        if (!getConfigured()) {
            log.error(sm.getString("standardContext.configurationFail"));
            ok = false;
        }

        // 获取资源，并且加入到上下文中
        if (ok) {
            getServletContext().setAttribute
                (Globals.RESOURCES_ATTR, getResources());

            if (getInstanceManager() == null) {
                javax.naming.Context context = null;
                if (isUseNaming() && getNamingContextListener() != null) {
                    context = getNamingContextListener().getEnvContext();
                }
                Map<String, Map<String, String>> injectionMap = buildInjectionMap(
                        getIgnoreAnnotations() ? new NamingResourcesImpl(): getNamingResources());
                setInstanceManager(new DefaultInstanceManager(context,
                        injectionMap, this, this.getClass().getClassLoader()));
            }
            getServletContext().setAttribute(
                    InstanceManager.class.getName(), getInstanceManager());
            InstanceManagerBindings.bind(getLoader().getClassLoader(), getInstanceManager());

            // 创建所需的上下文属性
            getServletContext().setAttribute(
                    JarScanner.class.getName(), getJarScanner());

            // Make the version info available
            getServletContext().setAttribute(Globals.WEBAPP_VERSION, getWebappVersion());
        }

        // Set up the context init params
        mergeParameters();

        // Call ServletContainerInitializers
        for (Map.Entry<ServletContainerInitializer, Set<Class<?>>> entry :
            initializers.entrySet()) {
            try {
                //创建application context
                entry.getKey().onStartup(entry.getValue(),
                        getServletContext());
            } catch (ServletException e) {
                log.error(sm.getString("standardContext.sciFail"), e);
                ok = false;
                break;
            }
        }

        // Configure and call application event listeners
        if (ok) {
            if (!listenerStart()) {
                log.error(sm.getString("standardContext.listenerFail"));
                ok = false;
            }
        }

        // Check constraints for uncovered HTTP methods
        // Needs to be after SCIs and listeners as they may programmatically
        // change constraints
        if (ok) {
            checkConstraintsForUncoveredMethods(findConstraints());
        }

        try {
            // Start manager
            Manager manager = getManager();
            if (manager instanceof Lifecycle) {
                ((Lifecycle) manager).start();
            }
        } catch(Exception e) {
            log.error(sm.getString("standardContext.managerFail"), e);
            ok = false;
        }

        // Configure and call application filters
        if (ok) {
            if (!filterStart()) {
                log.error(sm.getString("standardContext.filterFail"));
                ok = false;
            }
        }

        // Load and initialize all "load on startup" servlets
        if (ok) {
            if (!loadOnStartup(findChildren())){
                log.error(sm.getString("standardContext.servletFail"));
                ok = false;
            }
        }

        // Start ContainerBackgroundProcessor thread
        super.threadStart();
    } finally {
        // Unbinding thread
        unbindThread(oldCCL);
    }

    // Set available status depending upon startup success
    if (ok) {
        if (log.isDebugEnabled())
            log.debug("Starting completed");
    } else {
        log.error(sm.getString("standardContext.startFailed", getName()));
    }

    startTime=System.currentTimeMillis();

    // Send j2ee.state.running notification
    if (ok && (this.getObjectName() != null)) {
        Notification notification =
            new Notification("j2ee.state.running", this.getObjectName(),
                             sequenceNumber.getAndIncrement());
        broadcaster.sendNotification(notification);
    }
    getResources().gc();

    // Reinitializing if something went wrong
    if (!ok) {
        setState(LifecycleState.FAILED);
    } else {
        setState(LifecycleState.STARTING);
    }
}

上面设置生命周期状态后，启动监听器，会执行ContextConfig中的webConfig()方法：

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protected void webConfig() {
    //解析每个项目的web.xml  web3.0后有注解方式，所以有两种，有web.xml的情况，解析它，还要解析注解。
    WebXmlParser webXmlParser = new WebXmlParser(context.getXmlNamespaceAware(),
            context.getXmlValidation(), context.getXmlBlockExternal());

    Set<WebXml> defaults = new HashSet<>();
    defaults.add(getDefaultWebXmlFragment(webXmlParser));

    WebXml webXml = createWebXml();

    // 解析 web.xml
    InputSource contextWebXml = getContextWebXmlSource();
    if (!webXmlParser.parseWebXml(contextWebXml, webXml, false)) {
        ok = false;
    }

    ServletContext sContext = context.getServletContext();

    // 排序

    // Step 1. Identify all the JARs packaged with the application and those provided by the container. If any of the application JARs have a web-fragment.xml
    // it will be parsed at this point. web-fragment.xml files are ignored for container provided JARs.
    Map<String,WebXml> fragments = processJarsForWebFragments(webXml, webXmlParser);

    // Step 2. Order the fragments.
    Set<WebXml> orderedFragments = null;
    orderedFragments =
            WebXml.orderWebFragments(webXml, fragments, sContext);

    // Step 3. Look for ServletContainerInitializer implementations
    // 锁定servlet容器
    if (ok) {
        processServletContainerInitializers();
    }

    if  (!webXml.isMetadataComplete() || typeInitializerMap.size() > 0) {
        // Steps 4 & 5. 把web资源加载进来
        processClasses(webXml, orderedFragments);
    }

    if (!webXml.isMetadataComplete()) {
        // Step 6. Merge web-fragment.xml files into the main web.xml
        //将web-fragment.xml文件合并到主web.xml中
        // file.
        if (ok) {
            ok = webXml.merge(orderedFragments);
        }

        // Step 7. Apply global defaults Have to merge defaults before JSP conversion since defaults provide JSP servlet definition.
        webXml.merge(defaults);

        // Step 8. Convert explicitly mentioned jsps to servlets
        if (ok) {
            convertJsps(webXml);
        }

        // Step 9. Apply merged web.xml to Context
        if (ok) {
            configureContext(webXml);
        }
    } else {
        webXml.merge(defaults);
        convertJsps(webXml);
        configureContext(webXml);
    }

    if (context.getLogEffectiveWebXml()) {
        log.info("web.xml:\n" + webXml.toXml());
    }

    // Always need to look for static resources
    //查找打包在jar中的静态资源
    // Step 10. Look for static resources packaged in JARs
    if (ok) {
        // Spec does not define an order. Use ordered JARs followed by remaining JARs
        Set<WebXml> resourceJars = new LinkedHashSet<>();
        for (WebXml fragment : orderedFragments) {
            resourceJars.add(fragment);
        }
        for (WebXml fragment : fragments.values()) {
            if (!resourceJars.contains(fragment)) {
                resourceJars.add(fragment);
            }
        }
        processResourceJARs(resourceJars);
        // See also StandardContext.resourcesStart() for
        // WEB-INF/classes/META-INF/resources configuration
    }

    // Step 11. Apply the ServletContainerInitializer config to the
    // context
    if (ok) {
        for (Map.Entry<ServletContainerInitializer,
                Set<Class<?>>> entry :
                    initializerClassMap.entrySet()) {
            if (entry.getValue().isEmpty()) {
                context.addServletContainerInitializer(
                        entry.getKey(), null);
            } else {
                context.addServletContainerInitializer(
                        entry.getKey(), entry.getValue());
            }
        }
    }
}


protected void processClasses(WebXml webXml, Set<WebXml> orderedFragments) {
    // Step 4. Process /WEB-INF/classes for annotations and
    // @HandlesTypes matches
    Map<String, JavaClassCacheEntry> javaClassCache = new HashMap<>();

    if (ok) {
        ///WEB-INF/classes下所有资源
        WebResource[] webResources =
                context.getResources().listResources("/WEB-INF/classes");

        for (WebResource webResource : webResources) {
            // Skip the META-INF directory from any JARs that have been
            // expanded in to WEB-INF/classes (sometimes IDEs do this).
            if ("META-INF".equals(webResource.getName())) {
                continue;
            }
            //处理注解的资源
            processAnnotationsWebResource(webResource, webXml,
                    webXml.isMetadataComplete(), javaClassCache);
        }
    }

    // Step 5. Process JARs for annotations and
    // @HandlesTypes matches - only need to process those fragments we
    // are going to use (remember orderedFragments includes any
    // container fragments)
    if (ok) {
        processAnnotations(
                orderedFragments, webXml.isMetadataComplete(), javaClassCache);
    }

    // Cache, if used, is no longer required so clear it
    javaClassCache.clear();
}

Wrapper

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protected synchronized void startInternal() throws LifecycleException {

    // Send j2ee.state.starting notification 发送监听通知
    if (this.getObjectName() != null) {
        Notification notification = new Notification("j2ee.state.starting",
                                                    this.getObjectName(),
                                                    sequenceNumber++);
        broadcaster.sendNotification(notification);
    }

    // 执行父类方法
    super.startInternal();

    setAvailable(0L);

    // Send j2ee.state.running notification
    if (this.getObjectName() != null) {
        Notification notification =
            new Notification("j2ee.state.running", this.getObjectName(),
                            sequenceNumber++);
        broadcaster.sendNotification(notification);
    }

}

public synchronized void load() throws ServletException {
    instance = loadServlet();

    if (!instanceInitialized) {
        initServlet(instance);
    }

    if (isJspServlet) {
        StringBuilder oname = new StringBuilder(getDomain());

        oname.append(":type=JspMonitor");

        oname.append(getWebModuleKeyProperties());

        oname.append(",name=");
        oname.append(getName());

        oname.append(getJ2EEKeyProperties());

        try {
            jspMonitorON = new ObjectName(oname.toString());
            Registry.getRegistry(null, null).registerComponent(instance, jspMonitorON, null);
        } catch (Exception ex) {
            log.warn("Error registering JSP monitoring with jmx " + instance);
        }
    }
}

启动子容器流程如下：
20200405213810

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