Tomcat 系列篇九-介绍下 Tomcat 里的 ContainerBase

前面介绍过 Tomcat 的层次结构，

<Server>
    <Service>
        <Connector />
        <Connector />
        <Engine>
            <Host>
                <Context />
            </Host>
        </Engine>
    </Service>
</Server>

参考这个 xml，而对于这些组件中，有一类有相同的基类，也就是这次要介绍的 ContainerBase，

包括 engine，host，context 还有 wrapper ，都是同样的容器组件，
而他们共同实现的接口就是 Container ，
主要包含了

public static final String ADD_CHILD_EVENT = "addChild";


/**
 * The ContainerEvent event type sent when a valve is added
 * by <code>addValve()</code>, if this Container supports pipelines.
 */
public static final String ADD_VALVE_EVENT = "addValve";


/**
 * The ContainerEvent event type sent when a child container is removed
 * by <code>removeChild()</code>.
 */
public static final String REMOVE_CHILD_EVENT = "removeChild";


/**
 * The ContainerEvent event type sent when a valve is removed
 * by <code>removeValve()</code>, if this Container supports pipelines.
 */
public static final String REMOVE_VALVE_EVENT = "removeValve";

这几个事件类型，

public Pipeline getPipeline();

public Container getParent();

public void addChild(Container child);

public Container[] findChildren();

public int getStartStopThreads();

public void setStartStopThreads(int startStopThreads);

包括 pipeline 和获取 parent，添加 child 跟查找 child，然后设置线程池的线程数等
而对于 ContainerBase
也包含了 Lifecycle 的常规方法

@Override
protected void initInternal() throws LifecycleException {
    reconfigureStartStopExecutor(getStartStopThreads());
    super.initInternal();
}


private void reconfigureStartStopExecutor(int threads) {
    if (threads == 1) {
        // Use a fake executor
        if (!(startStopExecutor instanceof InlineExecutorService)) {
            startStopExecutor = new InlineExecutorService();
        }
    } else {
        // Delegate utility execution to the Service
        Server server = Container.getService(this).getServer();
        server.setUtilityThreads(threads);
        startStopExecutor = server.getUtilityExecutor();
    }
}

初始化方法主要就是之前讲过的线程池
后面就开始 startInternal

@Override
    protected synchronized void startInternal() throws LifecycleException {

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

        // Start our child containers, if any
        Container children[] = findChildren();
        List<Future<Void>> results = new ArrayList<>();
        for (Container child : children) {
            results.add(startStopExecutor.submit(new StartChild(child)));
        }

        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());
        }

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

        setState(LifecycleState.STARTING);

        // Start our thread
        if (backgroundProcessorDelay > 0) {
            monitorFuture = Container.getService(ContainerBase.this).getServer()
                    .getUtilityExecutor().scheduleWithFixedDelay(
                            new ContainerBackgroundProcessorMonitor(), 0, 60, TimeUnit.SECONDS);
        }
    }

这里包括了 cluster 的启动和 realm 的启动，然后将 child 子组件添加到线程池里启动，然后循环 get 结果，接下去就是 pipeline 的启动，设置开始中状态，后面是 ContainerBackgroundProcessor 的启动
然后是停止方法

@Override
    protected synchronized void stopInternal() throws LifecycleException {

        // Stop our thread
        if (monitorFuture != null) {
            monitorFuture.cancel(true);
            monitorFuture = null;
        }
        threadStop();

        setState(LifecycleState.STOPPING);

        // Stop the Valves in our pipeline (including the basic), if any
        if (pipeline instanceof Lifecycle &&
                ((Lifecycle) pipeline).getState().isAvailable()) {
            ((Lifecycle) pipeline).stop();
        }

        // Stop our child containers, if any
        Container children[] = findChildren();
        List<Future<Void>> results = new ArrayList<>();
        for (Container child : children) {
            results.add(startStopExecutor.submit(new StopChild(child)));
        }

        boolean fail = false;
        for (Future<Void> result : results) {
            try {
                result.get();
            } catch (Exception e) {
                log.error(sm.getString("containerBase.threadedStopFailed"), e);
                fail = true;
            }
        }
        if (fail) {
            throw new LifecycleException(
                    sm.getString("containerBase.threadedStopFailed"));
        }

        // Stop our subordinate components, if any
        Realm realm = getRealmInternal();
        if (realm instanceof Lifecycle) {
            ((Lifecycle) realm).stop();
        }
        Cluster cluster = getClusterInternal();
        if (cluster instanceof Lifecycle) {
            ((Lifecycle) cluster).stop();
        }
    }

也是类似的，只不过停止顺序和刚才开始的顺序反了一下