Tomcat源码分析(二)-Tomcat的启动流程以及分析

整个Tomcat的启动图：

 

Bootstrap类：

  /**
     * Main method and entry point when starting Tomcat via the provided
     * scripts.
     *
     * @param args Command line arguments to be processed
     */
    public static void main(String args[]) {

        if (daemon == null) {
            // Don't set daemon until init() has completed
            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();
            } 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);
        }

    }

   Bootstrap类：
   /**
     * Initialize daemon.
     */
    public void init() throws Exception {

        initClassLoaders();

        Thread.currentThread().setContextClassLoader(catalinaLoader);

        SecurityClassLoad.securityClassLoad(catalinaLoader);

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

        // Set the shared extensions class loader
        if (log.isDebugEnabled())
            log.debug("Setting startup class properties");
        String methodName = "setParentClassLoader";
        Class<?> paramTypes[] = new Class[1];
        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);

        catalinaDaemon = startupInstance;

    }

 

当运行到 command是"start"时 代码如下：

 if (command.equals("start")) {
                daemon.setAwait(true);
                daemon.load(args);
                daemon.start();
            } 

 /**
     * Start the Catalina daemon.
     */
    public void start()
        throws Exception {
        if( catalinaDaemon==null ) init();

        Method method = catalinaDaemon.getClass().getMethod("start", (Class [] )null);
        method.invoke(catalinaDaemon, (Object [])null);

    }

通过Method反射调用了catalinaDaemon的start方法。而catalinaDaemon对象在init()初始化的时候通过

 catalinaDaemon = startupInstance;已经赋值。而startupInstance正是org.apache.catalina.startup.Catalina类。

所以就相当于 (Catalina)catalinaDaemon.start()方法。

daemon.setAwait(true); setAwait方法设置Server启动完成后是否进入等待状态的标志。

 daemon.load(args); load方法用于加载配置文件,创建并初始化Server.

   /**
     * Load daemon.
     */
    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;
        }
        Method method =
            catalinaDaemon.getClass().getMethod(methodName, paramTypes);
        if (log.isDebugEnabled())
            log.debug("Calling startup class " + method);
        method.invoke(catalinaDaemon, param);

    }

通过反射调用了Catalina类的load方法。

1、Catalina类load方法：

  /**
     * Start a new server instance.
     */
    public void load() {

        if (loaded) {
            return;
        }
        loaded = true;

        long t1 = System.nanoTime();

        initDirs();

        // Before digester - it may be needed
        initNaming();

        // Create and execute our Digester
        Digester digester = createStartDigester();

        InputSource inputSource = null;
        InputStream inputStream = null;
        File file = null;
        try {
            try {
                file = configFile(); //路径conf/server.xml
                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.w