tomcat源码分析系列之启动---暗度陈仓

    前面我们分析了tomcat是如何启动的，但我们好像并没有看到我们期待发生的诸如在什么地方启动了服务，什么地方启动了监听，好像只是做了些加载资源、设置环境变量等鸡毛蒜皮的事，这到底是怎么回事？我们回顾一下前面提到的一个函数：解析server.xml的函数

 protected Digester createStartDigester() {
        long t1=System.currentTimeMillis();
        // Initialize the digester
        Digester digester = new Digester();
        digester.setValidating(false);
        digester.setRulesValidation(true);
        HashMap<Class<?>, List<String>> fakeAttributes =
            new HashMap<Class<?>, List<String>>();
        ArrayList<String> attrs = new ArrayList<String>();
        attrs.add("className");
        fakeAttributes.put(Object.class, attrs);
        digester.setFakeAttributes(fakeAttributes);
        digester.setClassLoader(StandardServer.class.getClassLoader());

        // Configure the actions we will be using
        digester.addObjectCreate("Server",
                                 "org.apache.catalina.core.StandardServer",
                                 "className");
        digester.addSetProperties("Server");
        digester.addSetNext("Server",
                            "setServer",
                            "org.apache.catalina.Server");

        digester.addObjectCreate("Server/GlobalNamingResources",
                                 "org.apache.catalina.deploy.NamingResources");
        digester.addSetProperties("Server/GlobalNamingResources");
        digester.addSetNext("Server/GlobalNamingResources",
                            "setGlobalNamingResources",
                            "org.apache.catalina.deploy.NamingResources");

        digester.addObjectCreate("Server/Listener",
                                 null, // MUST be specified in the element
                                 "className");
        digester.addSetProperties("Server/Listener");
        digester.addSetNext("Server/Listener",
                            "addLifecycleListener",
                            "org.apache.catalina.LifecycleListener");

        digester.addObjectCreate("Server/Service",
                                 "org.apache.catalina.core.StandardService",
                                 "className");
        digester.addSetProperties("Server/Service");
        digester.addSetNext("Server/Service",
                            "addService",
                            "org.apache.catalina.Service");

        digester.addObjectCreate("Server/Service/Listener",
                                 null, // MUST be specified in the element
                                 "className");
        digester.addSetProperties("Server/Service/Listener");
        digester.addSetNext("Server/Service/Listener",
                            "addLifecycleListener",
                            "org.apache.catalina.LifecycleListener");

        //Executor
        digester.addObjectCreate("Server/Service/Executor",
                         "org.apache.catalina.core.StandardThreadExecutor",
                         "className");
        digester.addSetProperties("Server/Service/Executor");

        digester.addSetNext("Server/Service/Executor",
                            "addExecutor",
                            "org.apache.catalina.Executor");


        digester.addRule("Server/Service/Connector",
                         new ConnectorCreateRule());
        digester.addRule("Server/Service/Connector",
                         new SetAllPropertiesRule(new String[]{"executor"}));
        digester.addSetNext("Server/Service/Connector",
                            "addConnector",
                            "org.apache.catalina.connector.Connector");


        digester.addObjectCreate("Server/Service/Connector/Listener",
                                 null, // MUST be specified in the element
                                 "className");
        digester.addSetProperties("Server/Service/Connector/Listener");
        digester.addSetNext("Server/Service/Connector/Listener",
                            "addLifecycleListener",
                            "org.apache.catalina.LifecycleListener");

        // Add RuleSets for nested elements
        digester.addRuleSet(new NamingRuleSet("Server/GlobalNamingResources/"));
        digester.addRuleSet(new EngineRuleSet("Server/Service/"));
        digester.addRuleSet(new HostRuleSet("Server/Service/Engine/"));
        digester.addRuleSet(new ContextRuleSet("Server/Service/Engine/Host/"));
        digester.addRuleSet(new ClusterRuleSet("Server/Service/Engine/Host/Cluster/"));
        digester.addRuleSet(new NamingRuleSet("Server/Service/Engine/Host/Context/"));

        // When the 'engine' is found, set the parentClassLoader.
        digester.addRule("Server/Service/Engine",
                         new SetParentClassLoaderRule(parentClassLoader));
        digester.addRuleSet(new ClusterRuleSet("Server/Service/Engine/Cluster/"));

        long t2=System.currentTimeMillis();
        if (log.isDebugEnabled())
            log.debug("Digester for server.xml created " + ( t2-t1 ));
        return (digester);

    }

    在前面我们并没有详细去看这个函数，只是知道它解析了server.xml文件，现在我们深入这个方法看一下。这个方法里反复调用了下面三个方法：

addObjectCreate，addSetProperties，addSetNext

 我们看一下这三个方法到底做了些什么。

/**
     * Add an "object create" rule for the specified parameters.
     *添加一个“创建对象”的规则
     * @param pattern Element matching pattern 匹配模式
     * @param className Default Java class name to be created 默认要实例的java类
     * @param attributeName Attribute name that optionally overrides
     *  the default Java class name to be created
     * @see ObjectCreateRule 
     */
    public void addObjectCreate(String pattern, String className,
                                String attributeName) {

        addRule(pattern,
                new ObjectCreateRule(className, attributeName));

    }

 这个方法就是定义了一个创建对象的规则：匹配的规则（遇到server.xml里什么样的表达式），默认要实例化的类名，默认的一个属性名（xml配置属性）。就是说如果server.xml里遇到跟规则相匹配的项，如果没有设定指定attributeName属性的值，则使用这里设置的默认的类。

/**
     * Add a "set properties" rule for the specified parameters.
     *
     * @param pattern Element matching pattern
     * @see SetPropertiesRule
     */
    public void addSetProperties(String pattern) {

        addRule(pattern,
                new SetPropertiesRule());

    }

 定义了一个调用setter方法的规则：把这个值设置给谁

/**
     * Add a "set next" rule for the specified parameters.
     *
     * @param pattern Element matching pattern
     * @param methodName Method name to call on the parent element
     * @param paramType Java class name of the expected parameter type
     *  (if you wish to use a primitive type, specify the corresponding
     *  Java wrapper class instead, such as <code>java.lang.Boolean</code>
     *  for a <code>boolean</code> parameter)
     * @see SetNextRule
     */
    public void addSetNext(String pattern, String methodName,
                           String paramType) {

        addRule(pattern,
                new SetNextRule(methodName, paramType));

    }

 这个方法很关键，第一个参数依旧是匹配的规则，第二个参数是要调用父元素的方法名，第三个参数是方法需要的参数类型。看到这个我们或许明白了点。我们再回头看下前面提到的方法：

digester.addObjectCreate("Server",
                                 "org.apache.catalina.core.StandardServer",
                                 "className");
        digester.addSetProperties("Server");
        digester.addSetNext("Server",
                            "setServer",
                            "org.apache.catalina.Server");

 上面这几句话就是说，遇到Server，如果没有设置className属性，就实例化org.apache.catalina.core.StandardServer的一个对象（如果设置了className,就使用设置的Class），把这个对象赋值给Catalina的server属性（调用server的setter方法）。

 

digester.addObjectCreate("Server/GlobalNamingResources",
                                 "org.apache.catalina.deploy.NamingResources");
        digester.addSetProperties("Server/GlobalNamingResources");
        digester.addSetNext("Server/GlobalNamingResources",
                            "setGlobalNamingResources",
                            "org.apache.catalina.deploy.NamingResources");

匹配到server的下级节点： GlobalNamingResources，就创建一个org.apache.catalina.deploy.NamingResources的实例，调用server的setGlobalNamingResources方法。其他的类似，再次不一一赘述。但有一个方法我们不能漏掉：StandardServer下的addService方法（StandardService下的addExecutor方法、StandardServic下的addConnector方法与它类似）：

/**
     * Add a new Service to the set of defined Services.
     *
     * @param service The Service to be added
     */
    @Override
    public void addService(Service service) {

        service.setServer(this);

        synchronized (services) {
            Service results[] = new Service[services.length + 1];
            System.arraycopy(services, 0, results, 0, services.length);
            results[services.length] = service;
            services = results;

            if (getState().isAvailable()) {
                try {
                    service.start();
                } catch (LifecycleException e) {
                    // Ignore
                }
            }

            // Report this property change to interested listeners
            support.firePropertyChange("service", null, service);
        }

    }

 这个方法除了调用setter外，还做了一件重要的事情： service.start();这个start方法属于Lifecycle接口，在LifecycleBase里实现，

@Override
    public final synchronized void init() throws LifecycleException {
        if (!state.equals(LifecycleState.NEW)) {
            invalidTransition(Lifecycle.BEFORE_INIT_EVENT);
        }
        setStateInternal(LifecycleState.INITIALIZING, null, false);

        try {
            initInternal();
        } catch (LifecycleException e) {
            setStateInternal(LifecycleState.FAILED, null, false);
            throw e;
        }

        setStateInternal(LifecycleState.INITIALIZED, null, false);
    }
    
    
    protected abstract void initInternal() throws LifecycleException;
    
    /**
     * {@inheritDoc}
     */
    @Override
    public final synchronized void start() throws LifecycleException {
        
        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.INITIALIZED) &&
                !state.equals(LifecycleState.STOPPED)) {
            invalidTransition(Lifecycle.BEFORE_START_EVENT);
        }

        setStateInternal(LifecycleState.STARTING_PREP, null, false);

        try {
            startInternal();
        } catch (LifecycleException e) {
            setStateInternal(LifecycleState.FAILED, null, false);
            throw e;
        }

        if (state.equals(LifecycleState.FAILED) ||
                state.equals(LifecycleState.MUST_STOP)) {
            stop();
        } else {
            // Shouldn't be necessary but acts as a check that sub-classes are
            // doing what they are supposed to.
            if (!state.equals(LifecycleState.STARTING)) {
                invalidTransition(Lifecycle.AFTER_START_EVENT);
            }
            
            setStateInternal(LifecycleState.STARTED, null, false);
        }
    }


    /**
     * Sub-classes must ensure that the state is changed to
     * {@link LifecycleState#STARTING} during the execution of this method.
     * Changing state will trigger the {@link Lifecycle#START_EVENT} event.
     * 
     * If a component fails to start it may either throw a
     * {@link LifecycleException} which will cause it's parent to fail to start
     * or it can place itself in the error state in which case {@link #stop()}
     * will be called on the failed component but the parent component will
     * continue to start normally.
     * 
     * @throws LifecycleException
     */
    protected abstract void startInternal() throws LifecycleException;

  LifecycleBase的start方法是一个典型的Template Method 模式。在分析这个之前，我先看一下类关系图：

LifecycleBase最后又调用个实现类里的initInternal和startInternal方法，所以我们只需要看具体类里的这两个方法就可以了。

StandardService里的initInternal

/**
     * Invoke a pre-startup initialization. This is used to allow connectors
     * to bind to restricted ports under Unix operating environments.
     */
    @Override
    protected void initInternal() throws LifecycleException {

        super.initInternal();
        
        if (container != null) {
            container.init();
        }

        // Initialize any Executors
        for (Executor executor : findExecutors()) {
            if (executor instanceof LifecycleMBeanBase) {
                ((LifecycleMBeanBase) executor).setDomain(getDomain());
            }
            executor.init();
        }

        // Initialize our defined Connectors
        synchronized (connectors) {
            for (Connector connector : connectors) {
                try {
                    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);
                }
            }
        }
    }
    

 startInternal

/**
     * Start nested components ({@link Executor}s, {@link Connector}s and
     * {@link Container}s) 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 void startInternal() throws LifecycleException {

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

        // Start our defined Container first
        if (container != null) {
            synchronized (container) {
                container.start();
            }
        }

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

        // Start our defined Connectors second
        synchronized (connectors) {
            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);
                }
            }
        }
    }

 init和start的顺序都是这样的：Catalina->Server->Service.Service里启动了Container、Executor、Connector

ContainerBase的startInternal方法：

/**
     * 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 subordinate components, if any
        if ((loader != null) && (loader instanceof Lifecycle))
            ((Lifecycle) loader).start();
        logger = null;
        getLogger();
        if ((logger != null) && (logger instanceof Lifecycle))
            ((Lifecycle) logger).start();
        if ((manager != null) && (manager instanceof Lifecycle))
            ((Lifecycle) manager).start();
        if ((cluster != null) && (cluster instanceof Lifecycle))
            ((Lifecycle) cluster).start();
        if ((realm != null) && (realm instanceof Lifecycle))
            ((Lifecycle) realm).start();
        if ((resources != null) && (resources instanceof Lifecycle))
            ((Lifecycle) resources).start();

        // Start our child containers, if any
        Container children[] = findChildren();
        for (int i = 0; i < children.length; i++) {
            children[i].start();
        }

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


        setState(LifecycleState.STARTING);

        // Start our thread
        threadStart();

    }

  Conector的initInternal和startInternal方法

 @Override
    protected void initInternal() throws LifecycleException {

        super.initInternal();
        
        // Initialize adapter
        adapter = new CoyoteAdapter(this);
        protocolHandler.setAdapter(adapter);

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

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

        // Initialize mapper listener
        mapperListener.init();
    }


    /**
     * Begin processing requests via this Connector.
     *
     * @exception LifecycleException if a fatal startup error occurs
     */
    @Override
    protected void startInternal() throws LifecycleException {

        // Validate settings before starting
        if (getPort() < 1) {
            throw new LifecycleException(sm.getString(
                    "coyoteConnector.invalidPort", Integer.valueOf(getPort())));
        }

        setState(LifecycleState.STARTING);

        try {
            protocolHandler.start();
        } catch (Exception e) {
            String errPrefix = "";
            if(this.service != null) {
                errPrefix += "service.getName(): \"" + this.service.getName() + "\"; ";
            }

            throw new LifecycleException
                (errPrefix + " " + sm.getString
                 ("coyoteConnector.protocolHandlerStartFailed"), e);
        }

        mapperListener.start();
    }

 从上面的代码我们可以看出，父容器在启动时会把下面所有的组件都启动起来。Connector在启动的时候调用了protocolHandler.start();这个protocolHandler会是什么呢？它是Http11Protocol的实例，这个类就是http1.1 协议的一个实现类，就是真正解析、处理请求的地方。接下来我们会去分析一下这个类以及由它引申出来的内容。