/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.core;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.io.File;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import javax.management.ObjectName;

import org.apache.catalina.AccessLog;
import org.apache.catalina.Cluster;
import org.apache.catalina.Container;
import org.apache.catalina.ContainerEvent;
import org.apache.catalina.ContainerListener;
import org.apache.catalina.Context;
import org.apache.catalina.Engine;
import org.apache.catalina.Globals;
import org.apache.catalina.Host;
import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.Loader;
import org.apache.catalina.Pipeline;
import org.apache.catalina.Realm;
import org.apache.catalina.Server;
import org.apache.catalina.Valve;
import org.apache.catalina.Wrapper;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.catalina.util.ContextName;
import org.apache.catalina.util.LifecycleMBeanBase;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.ExceptionUtils;
import org.apache.tomcat.util.MultiThrowable;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.threads.InlineExecutorService;


Abstract implementation of the Container interface, providing common
functionality required by nearly every implementation.  Classes extending
this base class must may implement a replacement for invoke().

All subclasses of this abstract base class will include support for a
Pipeline object that defines the processing to be performed for each request
received by the invoke() method of this class, utilizing the
"Chain of Responsibility" design pattern.  A subclass should encapsulate its
own processing functionality as a Valve, and configure this
Valve into the pipeline by calling setBasic().

This implementation fires property change events, per the JavaBeans design
pattern, for changes in singleton properties.  In addition, it fires the
following ContainerEvent events to listeners who register
themselves with addContainerListener():

  
ContainerEvents fired by this implementation
  

    
Type
    
Data
    
Description
  
  

    
addChild
    
Container
    
Child container added to this Container.
  
  

    
pipeline.addValve
    
Valve
    
Valve added to this Container.
  
  

    
removeChild
    
Container
    
Child container removed from this Container.
  
  

    
pipeline.removeValve
    
Valve
    
Valve removed from this Container.
  
  

    
start
    
null
    
Container was started.
  
  

    
stop
    
null
    
Container was stopped.
  

Subclasses that fire additional events should document them in the
class comments of the implementation class.
Author:
Craig R. McClanahan/**
 * Abstract implementation of the <b>Container</b> interface, providing common
 * functionality required by nearly every implementation.  Classes extending
 * this base class must may implement a replacement for <code>invoke()</code>.
 * <p>
 * All subclasses of this abstract base class will include support for a
 * Pipeline object that defines the processing to be performed for each request
 * received by the <code>invoke()</code> method of this class, utilizing the
 * "Chain of Responsibility" design pattern.  A subclass should encapsulate its
 * own processing functionality as a <code>Valve</code>, and configure this
 * Valve into the pipeline by calling <code>setBasic()</code>.
 * <p>
 * This implementation fires property change events, per the JavaBeans design
 * pattern, for changes in singleton properties.  In addition, it fires the
 * following <code>ContainerEvent</code> events to listeners who register
 * themselves with <code>addContainerListener()</code>:
 * <table border=1>
 *   <caption>ContainerEvents fired by this implementation</caption>
 *   <tr>
 *     <th>Type</th>
 *     <th>Data</th>
 *     <th>Description</th>
 *   </tr>
 *   <tr>
 *     <td><code>addChild</code></td>
 *     <td><code>Container</code></td>
 *     <td>Child container added to this Container.</td>
 *   </tr>
 *   <tr>
 *     <td><code>{@link #getPipeline() pipeline}.addValve</code></td>
 *     <td><code>Valve</code></td>
 *     <td>Valve added to this Container.</td>
 *   </tr>
 *   <tr>
 *     <td><code>removeChild</code></td>
 *     <td><code>Container</code></td>
 *     <td>Child container removed from this Container.</td>
 *   </tr>
 *   <tr>
 *     <td><code>{@link #getPipeline() pipeline}.removeValve</code></td>
 *     <td><code>Valve</code></td>
 *     <td>Valve removed from this Container.</td>
 *   </tr>
 *   <tr>
 *     <td><code>start</code></td>
 *     <td><code>null</code></td>
 *     <td>Container was started.</td>
 *   </tr>
 *   <tr>
 *     <td><code>stop</code></td>
 *     <td><code>null</code></td>
 *     <td>Container was stopped.</td>
 *   </tr>
 * </table>
 * Subclasses that fire additional events should document them in the
 * class comments of the implementation class.
 *
 * @author Craig R. McClanahan
 */
public abstract class ContainerBase extends LifecycleMBeanBase
        implements Container {

    private static final Log log = LogFactory.getLog(ContainerBase.class);

    
Perform addChild with the permissions of this class.
addChild can be called with the XML parser on the stack,
this allows the XML parser to have fewer privileges than
Tomcat.
/**
     * Perform addChild with the permissions of this class.
     * addChild can be called with the XML parser on the stack,
     * this allows the XML parser to have fewer privileges than
     * Tomcat.
     */
    protected class PrivilegedAddChild implements PrivilegedAction<Void> {

        private final Container child;

        PrivilegedAddChild(Container child) {
            this.child = child;
        }

        @Override
        public Void run() {
            addChildInternal(child);
            return null;
        }

    }


    // ----------------------------------------------------- Instance Variables


    
The child Containers belonging to this Container, keyed by name.
/**
     * The child Containers belonging to this Container, keyed by name.
     */
    protected final HashMap<String, Container> children = new HashMap<>();


    
The processor delay for this component.
/**
     * The processor delay for this component.
     */
    protected int backgroundProcessorDelay = -1;


    
The future allowing control of the background processor.
/**
     * The future allowing control of the background processor.
     */
    protected ScheduledFuture<?> backgroundProcessorFuture;
    protected ScheduledFuture<?> monitorFuture;

    
The container event listeners for this Container. Implemented as a
CopyOnWriteArrayList since listeners may invoke methods to add/remove
themselves or other listeners and with a ReadWriteLock that would trigger
a deadlock.
/**
     * The container event listeners for this Container. Implemented as a
     * CopyOnWriteArrayList since listeners may invoke methods to add/remove
     * themselves or other listeners and with a ReadWriteLock that would trigger
     * a deadlock.
     */
    protected final List<ContainerListener> listeners = new CopyOnWriteArrayList<>();

    
The Logger implementation with which this Container is associated.
/**
     * The Logger implementation with which this Container is associated.
     */
    protected Log logger = null;


    
Associated logger name.
/**
     * Associated logger name.
     */
    protected String logName = null;


    
The cluster with which this Container is associated.
/**
     * The cluster with which this Container is associated.
     */
    protected Cluster cluster = null;
    private final ReadWriteLock clusterLock = new ReentrantReadWriteLock();


    
The human-readable name of this Container.
/**
     * The human-readable name of this Container.
     */
    protected String name = null;


    
The parent Container to which this Container is a child.
/**
     * The parent Container to which this Container is a child.
     */
    protected Container parent = null;


    
The parent class loader to be configured when we install a Loader.
/**
     * The parent class loader to be configured when we install a Loader.
     */
    protected ClassLoader parentClassLoader = null;


    
The Pipeline object with which this Container is associated.
/**
     * The Pipeline object with which this Container is associated.
     */
    protected final Pipeline pipeline = new StandardPipeline(this);


    
The Realm with which this Container is associated.
/**
     * The Realm with which this Container is associated.
     */
    private volatile Realm realm = null;


    
Lock used to control access to the Realm.
/**
     * Lock used to control access to the Realm.
     */
    private final ReadWriteLock realmLock = new ReentrantReadWriteLock();


    
The string manager for this package.
/**
     * The string manager for this package.
     */
    protected static final StringManager sm =
        StringManager.getManager(Constants.Package);


    
Will children be started automatically when they are added.
/**
     * Will children be started automatically when they are added.
     */
    protected boolean startChildren = true;

    
The property change support for this component.
/**
     * The property change support for this component.
     */
    protected final PropertyChangeSupport support =
            new PropertyChangeSupport(this);


    
The access log to use for requests normally handled by this container
that have been handled earlier in the processing chain.
/**
     * The access log to use for requests normally handled by this container
     * that have been handled earlier in the processing chain.
     */
    protected volatile AccessLog accessLog = null;
    private volatile boolean accessLogScanComplete = false;


    
The number of threads available to process start and stop events for any
children associated with this container.
/**
     * The number of threads available to process start and stop events for any
     * children associated with this container.
     */
    private int startStopThreads = 1;
    protected ExecutorService startStopExecutor;


    // ------------------------------------------------------------- Properties

    @Override
    public int getStartStopThreads() {
        return startStopThreads;
    }

    @Override
    public void setStartStopThreads(int startStopThreads) {
        int oldStartStopThreads = this.startStopThreads;
        this.startStopThreads = startStopThreads;

        // Use local copies to ensure thread safety
        if (oldStartStopThreads != startStopThreads && startStopExecutor != null) {
            reconfigureStartStopExecutor(getStartStopThreads());
        }
    }


    
Get the delay between the invocation of the backgroundProcess method on
this container and its children. Child containers will not be invoked
if their delay value is not negative (which would mean they are using
their own thread). Setting this to a positive value will cause
a thread to be spawn. After waiting the specified amount of time,
the thread will invoke the executePeriodic method on this container
and all its children.
/**
     * Get the delay between the invocation of the backgroundProcess method on
     * this container and its children. Child containers will not be invoked
     * if their delay value is not negative (which would mean they are using
     * their own thread). Setting this to a positive value will cause
     * a thread to be spawn. After waiting the specified amount of time,
     * the thread will invoke the executePeriodic method on this container
     * and all its children.
     */
    @Override
    public int getBackgroundProcessorDelay() {
        return backgroundProcessorDelay;
    }


    
Set the delay between the invocation of the execute method on this
container and its children.
Params:
delay – The delay in seconds between the invocation of
             backgroundProcess methods/**
     * Set the delay between the invocation of the execute method on this
     * container and its children.
     *
     * @param delay The delay in seconds between the invocation of
     *              backgroundProcess methods
     */
    @Override
    public void setBackgroundProcessorDelay(int delay) {
        backgroundProcessorDelay = delay;
    }


    
Return the Logger for this Container.
/**
     * Return the Logger for this Container.
     */
    @Override
    public Log getLogger() {
        if (logger != null)
            return logger;
        logger = LogFactory.getLog(getLogName());
        return logger;
    }


    
Returns:
the abbreviated name of this container for logging messages/**
     * @return the abbreviated name of this container for logging messages
     */
    @Override
    public String getLogName() {

        if (logName != null) {
            return logName;
        }
        String loggerName = null;
        Container current = this;
        while (current != null) {
            String name = current.getName();
            if ((name == null) || (name.equals(""))) {
                name = "/";
            } else if (name.startsWith("##")) {
                name = "/" + name;
            }
            loggerName = "[" + name + "]"
                + ((loggerName != null) ? ("." + loggerName) : "");
            current = current.getParent();
        }
        logName = ContainerBase.class.getName() + "." + loggerName;
        return logName;

    }


    
Return the Cluster with which this Container is associated.  If there is
no associated Cluster, return the Cluster associated with our parent
Container (if any); otherwise return null.
/**
     * Return the Cluster with which this Container is associated.  If there is
     * no associated Cluster, return the Cluster associated with our parent
     * Container (if any); otherwise return <code>null</code>.
     */
    @Override
    public Cluster getCluster() {
        Lock readLock = clusterLock.readLock();
        readLock.lock();
        try {
            if (cluster != null)
                return cluster;

            if (parent != null)
                return parent.getCluster();

            return null;
        } finally {
            readLock.unlock();
        }
    }


    /*
     * Provide access to just the cluster component attached to this container.
     */
    protected Cluster getClusterInternal() {
        Lock readLock = clusterLock.readLock();
        readLock.lock();
        try {
            return cluster;
        } finally {
            readLock.unlock();
        }
    }


    
Set the Cluster with which this Container is associated.
Params:
cluster – The newly associated Cluster/**
     * Set the Cluster with which this Container is associated.
     *
     * @param cluster The newly associated Cluster
     */
    @Override
    public void setCluster(Cluster cluster) {

        Cluster oldCluster = null;
        Lock writeLock = clusterLock.writeLock();
        writeLock.lock();
        try {
            // Change components if necessary
            oldCluster = this.cluster;
            if (oldCluster == cluster)
                return;
            this.cluster = cluster;

            // Stop the old component if necessary
            if (getState().isAvailable() && (oldCluster != null) &&
                (oldCluster instanceof Lifecycle)) {
                try {
                    ((Lifecycle) oldCluster).stop();
                } catch (LifecycleException e) {
                    log.error(sm.getString("containerBase.cluster.stop"), e);
                }
            }

            // Start the new component if necessary
            if (cluster != null)
                cluster.setContainer(this);

            if (getState().isAvailable() && (cluster != null) &&
                (cluster instanceof Lifecycle)) {
                try {
                    ((Lifecycle) cluster).start();
                } catch (LifecycleException e) {
                    log.error(sm.getString("containerBase.cluster.start"), e);
                }
            }
        } finally {
            writeLock.unlock();
        }

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


    
Return a name string (suitable for use by humans) that describes this
Container.  Within the set of child containers belonging to a particular
parent, Container names must be unique.
/**
     * Return a name string (suitable for use by humans) that describes this
     * Container.  Within the set of child containers belonging to a particular
     * parent, Container names must be unique.
     */
    @Override
    public String getName() {
        return name;
    }


    
Set a name string (suitable for use by humans) that describes this
Container.  Within the set of child containers belonging to a particular
parent, Container names must be unique.
Params:
name – New name of this container
Throws:
IllegalStateException – if this Container has already been
 added to the children of a parent Container (after which the name
 may not be changed)/**
     * Set a name string (suitable for use by humans) that describes this
     * Container.  Within the set of child containers belonging to a particular
     * parent, Container names must be unique.
     *
     * @param name New name of this container
     *
     * @exception IllegalStateException if this Container has already been
     *  added to the children of a parent Container (after which the name
     *  may not be changed)
     */
    @Override
    public void setName(String name) {
        if (name == null) {
            throw new IllegalArgumentException(sm.getString("containerBase.nullName"));
        }
        String oldName = this.name;
        this.name = name;
        support.firePropertyChange("name", oldName, this.name);
    }


    
Return if children of this container will be started automatically when
they are added to this container.
Returns:
true if the children will be started/**
     * Return if children of this container will be started automatically when
     * they are added to this container.
     *
     * @return <code>true</code> if the children will be started
     */
    public boolean getStartChildren() {
        return startChildren;
    }


    
Set if children of this container will be started automatically when
they are added to this container.
Params:
startChildren – New value of the startChildren flag/**
     * Set if children of this container will be started automatically when
     * they are added to this container.
     *
     * @param startChildren New value of the startChildren flag
     */
    public void setStartChildren(boolean startChildren) {

        boolean oldStartChildren = this.startChildren;
        this.startChildren = startChildren;
        support.firePropertyChange("startChildren", oldStartChildren, this.startChildren);
    }


    
Return the Container for which this Container is a child, if there is
one.  If there is no defined parent, return null.
/**
     * Return the Container for which this Container is a child, if there is
     * one.  If there is no defined parent, return <code>null</code>.
     */
    @Override
    public Container getParent() {
        return parent;
    }


    
Set the parent Container to which this Container is being added as a
child.  This Container may refuse to become attached to the specified
Container by throwing an exception.
Params:
container – Container to which this Container is being added
 as a child
Throws:
IllegalArgumentException – if this Container refuses to become
 attached to the specified Container/**
     * Set the parent Container to which this Container is being added as a
     * child.  This Container may refuse to become attached to the specified
     * Container by throwing an exception.
     *
     * @param container Container to which this Container is being added
     *  as a child
     *
     * @exception IllegalArgumentException if this Container refuses to become
     *  attached to the specified Container
     */
    @Override
    public void setParent(Container container) {

        Container oldParent = this.parent;
        this.parent = container;
        support.firePropertyChange("parent", oldParent, this.parent);

    }


    
Return the parent class loader (if any) for this web application.
This call is meaningful only after a Loader has
been configured.
/**
     * Return the parent class loader (if any) for this web application.
     * This call is meaningful only <strong>after</strong> a Loader has
     * been configured.
     */
    @Override
    public ClassLoader getParentClassLoader() {
        if (parentClassLoader != null)
            return parentClassLoader;
        if (parent != null) {
            return parent.getParentClassLoader();
        }
        return ClassLoader.getSystemClassLoader();
    }


    
Set the parent class loader (if any) for this web application.
This call is meaningful only before a Loader has
been configured, and the specified value (if non-null) should be
passed as an argument to the class loader constructor.
Params:
parent – The new parent class loader/**
     * Set the parent class loader (if any) for this web application.
     * This call is meaningful only <strong>before</strong> a Loader has
     * been configured, and the specified value (if non-null) should be
     * passed as an argument to the class loader constructor.
     *
     *
     * @param parent The new parent class loader
     */
    @Override
    public void setParentClassLoader(ClassLoader parent) {
        ClassLoader oldParentClassLoader = this.parentClassLoader;
        this.parentClassLoader = parent;
        support.firePropertyChange("parentClassLoader", oldParentClassLoader,
                                   this.parentClassLoader);

    }


    
Return the Pipeline object that manages the Valves associated with
this Container.
/**
     * Return the Pipeline object that manages the Valves associated with
     * this Container.
     */
    @Override
    public Pipeline getPipeline() {
        return this.pipeline;
    }


    
Return the Realm with which this Container is associated.  If there is
no associated Realm, return the Realm associated with our parent
Container (if any); otherwise return null.
/**
     * Return the Realm with which this Container is associated.  If there is
     * no associated Realm, return the Realm associated with our parent
     * Container (if any); otherwise return <code>null</code>.
     */
    @Override
    public Realm getRealm() {

        Lock l = realmLock.readLock();
        l.lock();
        try {
            if (realm != null)
                return realm;
            if (parent != null)
                return parent.getRealm();
            return null;
        } finally {
            l.unlock();
        }
    }


    protected Realm getRealmInternal() {
        Lock l = realmLock.readLock();
        l.lock();
        try {
            return realm;
        } finally {
            l.unlock();
        }
    }

    
Set the Realm with which this Container is associated.
Params:
realm – The newly associated Realm/**
     * Set the Realm with which this Container is associated.
     *
     * @param realm The newly associated Realm
     */
    @Override
    public void setRealm(Realm realm) {

        Lock l = realmLock.writeLock();
        l.lock();
        try {
            // Change components if necessary
            Realm oldRealm = this.realm;
            if (oldRealm == realm)
                return;
            this.realm = realm;

            // Stop the old component if necessary
            if (getState().isAvailable() && (oldRealm != null) &&
                (oldRealm instanceof Lifecycle)) {
                try {
                    ((Lifecycle) oldRealm).stop();
                } catch (LifecycleException e) {
                    log.error(sm.getString("containerBase.realm.stop"), e);
                }
            }

            // Start the new component if necessary
            if (realm != null)
                realm.setContainer(this);
            if (getState().isAvailable() && (realm != null) &&
                (realm instanceof Lifecycle)) {
                try {
                    ((Lifecycle) realm).start();
                } catch (LifecycleException e) {
                    log.error(sm.getString("containerBase.realm.start"), e);
                }
            }

            // Report this property change to interested listeners
            support.firePropertyChange("realm", oldRealm, this.realm);
        } finally {
            l.unlock();
        }

    }


    // ------------------------------------------------------ Container Methods


    
Add a new child Container to those associated with this Container,
if supported.  Prior to adding this Container to the set of children,
the child's setParent() method must be called, with this
Container as an argument.  This method may thrown an
IllegalArgumentException if this Container chooses not
to be attached to the specified Container, in which case it is not added
Params:
child – New child Container to be added
Throws:
IllegalArgumentException – if this exception is thrown by
 the setParent() method of the child Container
IllegalArgumentException – if the new child does not have
 a name unique from that of existing children of this Container
IllegalStateException – if this Container does not support
 child Containers/**
     * Add a new child Container to those associated with this Container,
     * if supported.  Prior to adding this Container to the set of children,
     * the child's <code>setParent()</code> method must be called, with this
     * Container as an argument.  This method may thrown an
     * <code>IllegalArgumentException</code> if this Container chooses not
     * to be attached to the specified Container, in which case it is not added
     *
     * @param child New child Container to be added
     *
     * @exception IllegalArgumentException if this exception is thrown by
     *  the <code>setParent()</code> method of the child Container
     * @exception IllegalArgumentException if the new child does not have
     *  a name unique from that of existing children of this Container
     * @exception IllegalStateException if this Container does not support
     *  child Containers
     */
    @Override
    public void addChild(Container child) {
        if (Globals.IS_SECURITY_ENABLED) {
            PrivilegedAction<Void> dp =
                new PrivilegedAddChild(child);
            AccessController.doPrivileged(dp);
        } else {
            addChildInternal(child);
        }
    }

    private void addChildInternal(Container child) {

        if (log.isDebugEnabled()) {
            log.debug("Add child " + child + " " + this);
        }

        synchronized(children) {
            if (children.get(child.getName()) != null)
                throw new IllegalArgumentException(
                        sm.getString("containerBase.child.notUnique", child.getName()));
            child.setParent(this);  // May throw IAE
            children.put(child.getName(), child);
        }

        fireContainerEvent(ADD_CHILD_EVENT, child);

        // Start child
        // Don't do this inside sync block - start can be a slow process and
        // locking the children object can cause problems elsewhere
        try {
            if ((getState().isAvailable() ||
                    LifecycleState.STARTING_PREP.equals(getState())) &&
                    startChildren) {
                child.start();
            }
        } catch (LifecycleException e) {
            throw new IllegalStateException(sm.getString("containerBase.child.start"), e);
        }
    }


    
Add a container event listener to this component.
Params:
listener – The listener to add/**
     * Add a container event listener to this component.
     *
     * @param listener The listener to add
     */
    @Override
    public void addContainerListener(ContainerListener listener) {
        listeners.add(listener);
    }


    
Add a property change listener to this component.
Params:
listener – The listener to add/**
     * Add a property change listener to this component.
     *
     * @param listener The listener to add
     */
    @Override
    public void addPropertyChangeListener(PropertyChangeListener listener) {
        support.addPropertyChangeListener(listener);
    }


    
Return the child Container, associated with this Container, with
the specified name (if any); otherwise, return null
Params:
name – Name of the child Container to be retrieved/**
     * Return the child Container, associated with this Container, with
     * the specified name (if any); otherwise, return <code>null</code>
     *
     * @param name Name of the child Container to be retrieved
     */
    @Override
    public Container findChild(String name) {
        if (name == null) {
            return null;
        }
        synchronized (children) {
            return children.get(name);
        }
    }


    
Return the set of children Containers associated with this Container.
If this Container has no children, a zero-length array is returned.
/**
     * Return the set of children Containers associated with this Container.
     * If this Container has no children, a zero-length array is returned.
     */
    @Override
    public Container[] findChildren() {
        synchronized (children) {
            Container results[] = new Container[children.size()];
            return children.values().toArray(results);
        }
    }


    
Return the set of container listeners associated with this Container.
If this Container has no registered container listeners, a zero-length
array is returned.
/**
     * Return the set of container listeners associated with this Container.
     * If this Container has no registered container listeners, a zero-length
     * array is returned.
     */
    @Override
    public ContainerListener[] findContainerListeners() {
        ContainerListener[] results =
            new ContainerListener[0];
        return listeners.toArray(results);
    }


    
Remove an existing child Container from association with this parent
Container.
Params:
child – Existing child Container to be removed/**
     * Remove an existing child Container from association with this parent
     * Container.
     *
     * @param child Existing child Container to be removed
     */
    @Override
    public void removeChild(Container child) {

        if (child == null) {
            return;
        }

        try {
            if (child.getState().isAvailable()) {
                child.stop();
            }
        } catch (LifecycleException e) {
            log.error(sm.getString("containerBase.child.stop"), e);
        }

        boolean destroy = false;
        try {
            // child.destroy() may have already been called which would have
            // triggered this call. If that is the case, no need to destroy the
            // child again.
            if (!LifecycleState.DESTROYING.equals(child.getState())) {
                child.destroy();
                destroy = true;
            }
        } catch (LifecycleException e) {
            log.error(sm.getString("containerBase.child.destroy"), e);
        }

        if (!destroy) {
            fireContainerEvent(REMOVE_CHILD_EVENT, child);
        }

        synchronized(children) {
            if (children.get(child.getName()) == null)
                return;
            children.remove(child.getName());
        }

    }


    
Remove a container event listener from this component.
Params:
listener – The listener to remove/**
     * Remove a container event listener from this component.
     *
     * @param listener The listener to remove
     */
    @Override
    public void removeContainerListener(ContainerListener listener) {
        listeners.remove(listener);
    }


    
Remove a property change listener from this component.
Params:
listener – The listener to remove/**
     * Remove a property change listener from this component.
     *
     * @param listener The listener to remove
     */
    @Override
    public void removePropertyChangeListener(PropertyChangeListener listener) {

        support.removePropertyChangeListener(listener);

    }


    @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();
        }
    }


    
Start this component and implement the requirements of LifecycleBase.startInternal(). 
Throws:
LifecycleException – if this component detects a fatal error
 that prevents this component from being used/**
     * 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
        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);
        }
    }


    
Stop this component and implement the requirements of LifecycleBase.stopInternal(). 
Throws:
LifecycleException – if this component detects a fatal error
 that prevents this component from being used/**
     * Stop this component and implement the requirements
     * of {@link org.apache.catalina.util.LifecycleBase#stopInternal()}.
     *
     * @exception LifecycleException if this component detects a fatal error
     *  that prevents this component from being used
     */
    @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();
        }
    }

    @Override
    protected void destroyInternal() throws LifecycleException {

        Realm realm = getRealmInternal();
        if (realm instanceof Lifecycle) {
            ((Lifecycle) realm).destroy();
        }
        Cluster cluster = getClusterInternal();
        if (cluster instanceof Lifecycle) {
            ((Lifecycle) cluster).destroy();
        }

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

        // Remove children now this container is being destroyed
        for (Container child : findChildren()) {
            removeChild(child);
        }

        // Required if the child is destroyed directly.
        if (parent != null) {
            parent.removeChild(this);
        }

        // If init fails, this may be null
        if (startStopExecutor != null) {
            startStopExecutor.shutdownNow();
        }

        super.destroyInternal();
    }


    
Check this container for an access log and if none is found, look to the
parent. If there is no parent and still none is found, use the NoOp
access log.
/**
     * Check this container for an access log and if none is found, look to the
     * parent. If there is no parent and still none is found, use the NoOp
     * access log.
     */
    @Override
    public void logAccess(Request request, Response response, long time,
            boolean useDefault) {

        boolean logged = false;

        if (getAccessLog() != null) {
            getAccessLog().log(request, response, time);
            logged = true;
        }

        if (getParent() != null) {
            // No need to use default logger once request/response has been logged
            // once
            getParent().logAccess(request, response, time, (useDefault && !logged));
        }
    }

    @Override
    public AccessLog getAccessLog() {

        if (accessLogScanComplete) {
            return accessLog;
        }

        AccessLogAdapter adapter = null;
        Valve valves[] = getPipeline().getValves();
        for (Valve valve : valves) {
            if (valve instanceof AccessLog) {
                if (adapter == null) {
                    adapter = new AccessLogAdapter((AccessLog) valve);
                } else {
                    adapter.add((AccessLog) valve);
                }
            }
        }
        if (adapter != null) {
            accessLog = adapter;
        }
        accessLogScanComplete = true;
        return accessLog;
    }

    // ------------------------------------------------------- Pipeline Methods


    
Convenience method, intended for use by the digester to simplify the process of adding Valves to containers. See Pipeline.addValve(Valve) for full details. Components other than the digester should use getPipeline().addValve(Valve) in case a future implementation provides an alternative method for the digester to use. 
Params:
valve – Valve to be added
Throws:
IllegalArgumentException – if this Container refused to
 accept the specified Valve
IllegalArgumentException – if the specified Valve refuses to be
 associated with this Container
IllegalStateException – if the specified Valve is already
 associated with a different Container/**
     * Convenience method, intended for use by the digester to simplify the
     * process of adding Valves to containers. See
     * {@link Pipeline#addValve(Valve)} for full details. Components other than
     * the digester should use {@link #getPipeline()}.{@link #addValve(Valve)} in case a
     * future implementation provides an alternative method for the digester to
     * use.
     *
     * @param valve Valve to be added
     *
     * @exception IllegalArgumentException if this Container refused to
     *  accept the specified Valve
     * @exception IllegalArgumentException if the specified Valve refuses to be
     *  associated with this Container
     * @exception IllegalStateException if the specified Valve is already
     *  associated with a different Container
     */
    public synchronized void addValve(Valve valve) {

        pipeline.addValve(valve);
    }


    
Execute a periodic task, such as reloading, etc. This method will be
invoked inside the classloading context of this container. Unexpected
throwables will be caught and logged.
/**
     * Execute a periodic task, such as reloading, etc. This method will be
     * invoked inside the classloading context of this container. Unexpected
     * throwables will be caught and logged.
     */
    @Override
    public void backgroundProcess() {

        if (!getState().isAvailable())
            return;

        Cluster cluster = getClusterInternal();
        if (cluster != null) {
            try {
                cluster.backgroundProcess();
            } catch (Exception e) {
                log.warn(sm.getString("containerBase.backgroundProcess.cluster",
                        cluster), e);
            }
        }
        Realm realm = getRealmInternal();
        if (realm != null) {
            try {
                realm.backgroundProcess();
            } catch (Exception e) {
                log.warn(sm.getString("containerBase.backgroundProcess.realm", realm), e);
            }
        }
        Valve current = pipeline.getFirst();
        while (current != null) {
            try {
                current.backgroundProcess();
            } catch (Exception e) {
                log.warn(sm.getString("containerBase.backgroundProcess.valve", current), e);
            }
            current = current.getNext();
        }
        fireLifecycleEvent(Lifecycle.PERIODIC_EVENT, null);
    }


    @Override
    public File getCatalinaBase() {

        if (parent == null) {
            return null;
        }

        return parent.getCatalinaBase();
    }


    @Override
    public File getCatalinaHome() {

        if (parent == null) {
            return null;
        }

        return parent.getCatalinaHome();
    }


    // ------------------------------------------------------ Protected Methods

    
Notify all container event listeners that a particular event has
occurred for this Container.  The default implementation performs
this notification synchronously using the calling thread.
Params:
type – Event type
data – Event data/**
     * Notify all container event listeners that a particular event has
     * occurred for this Container.  The default implementation performs
     * this notification synchronously using the calling thread.
     *
     * @param type Event type
     * @param data Event data
     */
    @Override
    public void fireContainerEvent(String type, Object data) {

        if (listeners.size() < 1)
            return;

        ContainerEvent event = new ContainerEvent(this, type, data);
        // Note for each uses an iterator internally so this is safe
        for (ContainerListener listener : listeners) {
            listener.containerEvent(event);
        }
    }


    // -------------------- JMX and Registration  --------------------

    @Override
    protected String getDomainInternal() {

        Container p = this.getParent();
        if (p == null) {
            return null;
        } else {
            return p.getDomain();
        }
    }


    @Override
    public String getMBeanKeyProperties() {
        Container c = this;
        StringBuilder keyProperties = new StringBuilder();
        int containerCount = 0;

        // Work up container hierarchy, add a component to the name for
        // each container
        while (!(c instanceof Engine)) {
            if (c instanceof Wrapper) {
                keyProperties.insert(0, ",servlet=");
                keyProperties.insert(9, c.getName());
            } else if (c instanceof Context) {
                keyProperties.insert(0, ",context=");
                ContextName cn = new ContextName(c.getName(), false);
                keyProperties.insert(9,cn.getDisplayName());
            } else if (c instanceof Host) {
                keyProperties.insert(0, ",host=");
                keyProperties.insert(6, c.getName());
            } else if (c == null) {
                // May happen in unit testing and/or some embedding scenarios
                keyProperties.append(",container");
                keyProperties.append(containerCount++);
                keyProperties.append("=null");
                break;
            } else {
                // Should never happen...
                keyProperties.append(",container");
                keyProperties.append(containerCount++);
                keyProperties.append('=');
                keyProperties.append(c.getName());
            }
            c = c.getParent();
        }
        return keyProperties.toString();
    }

    public ObjectName[] getChildren() {
        List<ObjectName> names = new ArrayList<>(children.size());
        for (Container next : children.values()) {
            if (next instanceof ContainerBase) {
                names.add(next.getObjectName());
            }
        }
        return names.toArray(new ObjectName[0]);
    }


    // -------------------- Background Thread --------------------

    
Start the background thread that will periodically check for
session timeouts.
/**
     * Start the background thread that will periodically check for
     * session timeouts.
     */
    protected void threadStart() {
        if (backgroundProcessorDelay > 0
                && (getState().isAvailable() || LifecycleState.STARTING_PREP.equals(getState()))
                && (backgroundProcessorFuture == null || backgroundProcessorFuture.isDone())) {
            if (backgroundProcessorFuture != null && backgroundProcessorFuture.isDone()) {
                // There was an error executing the scheduled task, get it and log it
                try {
                    backgroundProcessorFuture.get();
                } catch (InterruptedException | ExecutionException e) {
                    log.error(sm.getString("containerBase.backgroundProcess.error"), e);
                }
            }
            backgroundProcessorFuture = Container.getService(this).getServer().getUtilityExecutor()
                    .scheduleWithFixedDelay(new ContainerBackgroundProcessor(),
                            backgroundProcessorDelay, backgroundProcessorDelay,
                            TimeUnit.SECONDS);
        }
    }


    
Stop the background thread that is periodically checking for
session timeouts.
/**
     * Stop the background thread that is periodically checking for
     * session timeouts.
     */
    protected void threadStop() {
        if (backgroundProcessorFuture != null) {
            backgroundProcessorFuture.cancel(true);
            backgroundProcessorFuture = null;
        }
    }


    @Override
    public final String toString() {
        StringBuilder sb = new StringBuilder();
        Container parent = getParent();
        if (parent != null) {
            sb.append(parent.toString());
            sb.append('.');
        }
        sb.append(this.getClass().getSimpleName());
        sb.append('[');
        sb.append(getName());
        sb.append(']');
        return sb.toString();
    }

    // ------------------------------- ContainerBackgroundProcessor Inner Class

    protected class ContainerBackgroundProcessorMonitor implements Runnable {
        @Override
        public void run() {
            if (getState().isAvailable()) {
                threadStart();
            }
        }
    }

    
Private runnable class to invoke the backgroundProcess method
of this container and its children after a fixed delay.
/**
     * Private runnable class to invoke the backgroundProcess method
     * of this container and its children after a fixed delay.
     */
    protected class ContainerBackgroundProcessor implements Runnable {

        @Override
        public void run() {
            processChildren(ContainerBase.this);
        }

        protected void processChildren(Container container) {
            ClassLoader originalClassLoader = null;

            try {
                if (container instanceof Context) {
                    Loader loader = ((Context) container).getLoader();
                    // Loader will be null for FailedContext instances
                    if (loader == null) {
                        return;
                    }

                    // Ensure background processing for Contexts and Wrappers
                    // is performed under the web app's class loader
                    originalClassLoader = ((Context) container).bind(false, null);
                }
                container.backgroundProcess();
                Container[] children = container.findChildren();
                for (Container child : children) {
                    if (child.getBackgroundProcessorDelay() <= 0) {
                        processChildren(child);
                    }
                }
            } catch (Throwable t) {
                ExceptionUtils.handleThrowable(t);
                log.error(sm.getString("containerBase.backgroundProcess.error"), t);
            } finally {
                if (container instanceof Context) {
                    ((Context) container).unbind(false, originalClassLoader);
                }
            }
        }
    }


    // ---------------------------- Inner classes used with start/stop Executor

    private static class StartChild implements Callable<Void> {

        private Container child;

        public StartChild(Container child) {
            this.child = child;
        }

        @Override
        public Void call() throws LifecycleException {
            child.start();
            return null;
        }
    }

    private static class StopChild implements Callable<Void> {

        private Container child;

        public StopChild(Container child) {
            this.child = child;
        }

        @Override
        public Void call() throws LifecycleException {
            if (child.getState().isAvailable()) {
                child.stop();
            }
            return null;
        }
    }

}