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

        // Set Catalina path
        setCatalinaHome();
        setCatalinaBase();

        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.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;

    }

    /**
     * Start a new server instance.
     */
    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.error("Catalina.start: ", e);
        }

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

        try {
            // Register shutdown hook
            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);
                }
            }
        } catch (Throwable t) {
            // This will fail on JDK 1.2. Ignoring, as Tomcat can run
            // fine without the shutdown hook.
        }

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

    }

    /**
     * Await and shutdown.
     */
    public void await() {

        getServer().await();

    }

1. 创建socket连接的服务端对象ServerSocket；
2. 循环等待接收客户端发出的命令，如果接收到的命令与SHUTDOWN匹配（由于使用了equals，所以shutdown命令必须是大写的），那么退出循环等待。

    public void await() {
        // Negative values - don't wait on port - tomcat is embedded or we just don't like ports gja
        if( port == -2 ) {
            // undocumented yet - for embedding apps that are around, alive.
            return;
        }
        if( port==-1 ) {
            while( true ) {
                try {
                    Thread.sleep( 10000 );
                } catch( InterruptedException ex ) {
                }
                if( stopAwait ) return;
            }
        }
        
        // Set up a server socket to wait on
        ServerSocket serverSocket = null;
        try {
            serverSocket =
                new ServerSocket(port, 1,
                                 InetAddress.getByName(address));
        } catch (IOException e) {
            log.error("StandardServer.await: create[" + address
                               + ":" + port
                               + "]: ", e);
            System.exit(1);
        }

        // Loop waiting for a connection and a valid command
        while (true) {

            // Wait for the next connection
            Socket socket = null;
            InputStream stream = null;
            try {
                socket = serverSocket.accept();
                socket.setSoTimeout(10 * 1000);  // Ten seconds
                stream = socket.getInputStream();
            } catch (AccessControlException ace) {
                log.warn("StandardServer.accept security exception: "
                                   + ace.getMessage(), ace);
                continue;
            } catch (IOException e) {
                log.error("StandardServer.await: accept: ", e);
                System.exit(1);
            }

            // Read a set of characters from the socket
            StringBuilder command = new StringBuilder();
            int expected = 1024; // Cut off to avoid DoS attack
            while (expected < shutdown.length()) {
                if (random == null)
                    random = new Random();
                expected += (random.nextInt() % 1024);
            }
            while (expected > 0) {
                int ch = -1;
                try {
                    ch = stream.read();
                } catch (IOException e) {
                    log.warn("StandardServer.await: read: ", e);
                    ch = -1;
                }
                if (ch < 32)  // Control character or EOF terminates loop
                    break;
                command.append((char) ch);
                expected--;
            }

            // Close the socket now that we are done with it
            try {
                socket.close();
            } catch (IOException e) {
                // Ignore
            }

            // Match against our command string
            boolean match = command.toString().equals(shutdown);
            if (match) {
                log.info(sm.getString("standardServer.shutdownViaPort"));
                break;
            } else
                log.warn("StandardServer.await: Invalid command '" +
                                   command.toString() + "' received");

        }

        // Close the server socket and return
        try {
            serverSocket.close();
        } catch (IOException e) {
            // Ignore
        }

    }

sh shutdown.sh

os400=false
case "`uname`" in
OS400*) os400=true;;
esac

# resolve links - $0 may be a softlink
PRG="$0"

while [ -h "$PRG" ] ; do
  ls=`ls -ld "$PRG"`
  link=`expr "$ls" : '.*-> \(.*\)$'`
  if expr "$link" : '/.*' > /dev/null; then
    PRG="$link"
  else
    PRG=`dirname "$PRG"`/"$link"
  fi
done

PRGDIR=`dirname "$PRG"`
EXECUTABLE=catalina.sh

# Check that target executable exists
if $os400; then
  # -x will Only work on the os400 if the files are:
  # 1. owned by the user
  # 2. owned by the PRIMARY group of the user
  # this will not work if the user belongs in secondary groups
  eval
else
  if [ ! -x "$PRGDIR"/"$EXECUTABLE" ]; then
    echo "Cannot find $PRGDIR/$EXECUTABLE"
    echo "The file is absent or does not have execute permission"
    echo "This file is needed to run this program"
    exit 1
  fi
fi

exec "$PRGDIR"/"$EXECUTABLE" stop "$@"

• PRGDIR：当前shell脚本所在的路径；
• EXECUTABLE：脚本catalina.sh。

elif [ "$1" = "stop" ] ; then

  #省略参数校验脚本

  eval "\"$_RUNJAVA\"" $LOGGING_MANAGER $JAVA_OPTS \
    -Djava.endorsed.dirs="\"$JAVA_ENDORSED_DIRS\"" -classpath "\"$CLASSPATH\"" \
    -Dcatalina.base="\"$CATALINA_BASE\"" \
    -Dcatalina.home="\"$CATALINA_HOME\"" \
    -Djava.io.tmpdir="\"$CATALINA_TMPDIR\"" \
    org.apache.catalina.startup.Bootstrap "$@" stop

   /**
     * Stop the standalone server.
     */
    public void stopServer(String[] arguments)
        throws Exception {

        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("stopServer", paramTypes);
        method.invoke(catalinaDaemon, param);

    }

1. 创建Digester解析server.xml文件（此处只解析标签），以构造出Server容器（此时Server容器的子容器没有被实例化）；
2. 从实例化的Server容器获取Server的socket监听端口和地址，然后创建Socket对象连接启动Tomcat时创建的ServerSocket，最后向ServerSocket发送SHUTDOWN命令。根据代码清单9的内容，ServerSocket循环等待接收到SHUTDOWN命令后，最终调用stop方法停止Tomcat。

    public void stopServer() {
        stopServer(null);
    }

    public void stopServer(String[] arguments) {

        if (arguments != null) {
            arguments(arguments);
        }

        if( getServer() == null ) {
            // Create and execute our Digester
            Digester digester = createStopDigester();
            digester.setClassLoader(Thread.currentThread().getContextClassLoader());
            File file = configFile();
            try {
                InputSource is =
                    new InputSource("file://" + file.getAbsolutePath());
                FileInputStream fis = new FileInputStream(file);
                is.setByteStream(fis);
                digester.push(this);
                digester.parse(is);
                fis.close();
            } catch (Exception e) {
                log.error("Catalina.stop: ", e);
                System.exit(1);
            }
        }

        // Stop the existing server
        try {
            if (getServer().getPort()>0) { 
                Socket socket = new Socket(getServer().getAddress(),
                        getServer().getPort());
                OutputStream stream = socket.getOutputStream();
                String shutdown = getServer().getShutdown();
                for (int i = 0; i < shutdown.length(); i++)
                    stream.write(shutdown.charAt(i));
                stream.flush();
                stream.close();
                socket.close();
            } else {
                log.error(sm.getString("catalina.stopServer"));
                System.exit(1);
            }
        } catch (IOException e) {
            log.error("Catalina.stop: ", e);
            System.exit(1);
        }

    }

1. 将启动过程中添加的关闭钩子移除。Tomcat启动过程辛辛苦苦添加的关闭钩子为什么又要去掉呢？因为关闭钩子是为了在JVM异常退出后，进行资源的回收工作。主动停止Tomcat时调用的stop方法里已经包含了资源回收的内容，所以不再需要这个钩子了。
2. 停止Server容器。有关容器的停止内容，请阅读《Tomcat7.0源码分析——生命周期管理》一文。

    /**
     * Stop an existing server instance.
     */
    public void stop() {

        try {
            // Remove the ShutdownHook first so that server.stop() 
            // doesn't get invoked twice
            if (useShutdownHook) {
                Runtime.getRuntime().removeShutdownHook(shutdownHook);

                // If JULI is being used, re-enable JULI's shutdown to ensure
                // log messages are not lost jiaan
                LogManager logManager = LogManager.getLogManager();
                if (logManager instanceof ClassLoaderLogManager) {
                    ((ClassLoaderLogManager) logManager).setUseShutdownHook(
                            true);
                }
            }
        } catch (Throwable t) {
            // This will fail on JDK 1.2. Ignoring, as Tomcat can run
            // fine without the shutdown hook.
        }

        // Shut down the server
        try {
            getServer().stop();
        } catch (LifecycleException e) {
            log.error("Catalina.stop", e);
        }

    }

总结

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