/*
 * 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.loader;

import java.io.File;
import java.io.FilePermission;
import java.io.IOException;
import java.io.InputStream;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.ref.Reference;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.AccessControlException;
import java.security.AccessController;
import java.security.CodeSource;
import java.security.Permission;
import java.security.PermissionCollection;
import java.security.Policy;
import java.security.PrivilegedAction;
import java.security.ProtectionDomain;
import java.security.cert.Certificate;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.ConcurrentModificationException;
import java.util.Date;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.jar.Attributes;
import java.util.jar.Attributes.Name;
import java.util.jar.Manifest;

import org.apache.catalina.Container;
import org.apache.catalina.Globals;
import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleListener;
import org.apache.catalina.LifecycleState;
import org.apache.catalina.WebResource;
import org.apache.catalina.WebResourceRoot;
import org.apache.catalina.webresources.TomcatURLStreamHandlerFactory;
import org.apache.juli.WebappProperties;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.InstrumentableClassLoader;
import org.apache.tomcat.util.ExceptionUtils;
import org.apache.tomcat.util.IntrospectionUtils;
import org.apache.tomcat.util.compat.JreCompat;
import org.apache.tomcat.util.res.StringManager;
import org.apache.tomcat.util.security.PermissionCheck;

Specialized web application class loader.

This class loader is a full reimplementation of the
URLClassLoader from the JDK. It is designed to be fully
compatible with a normal URLClassLoader, although its internal
behavior may be completely different.

IMPLEMENTATION NOTE - By default, this class loader follows
the delegation model required by the specification. The system class
loader will be queried first, then the local repositories, and only then
delegation to the parent class loader will occur. This allows the web
application to override any shared class except the classes from J2SE.
Special handling is provided from the JAXP XML parser interfaces, the JNDI
interfaces, and the classes from the servlet API, which are never loaded
from the webapp repositories. The delegate property
allows an application to modify this behavior to move the parent class loader
ahead of the local repositories.

IMPLEMENTATION NOTE - Due to limitations in Jasper
compilation technology, any repository which contains classes from
the servlet API will be ignored by the class loader.

IMPLEMENTATION NOTE - The class loader generates source
URLs which include the full JAR URL when a class is loaded from a JAR file,
which allows setting security permission at the class level, even when a
class is contained inside a JAR.

IMPLEMENTATION NOTE - Local repositories are searched in
the order they are added via the initial constructor.

IMPLEMENTATION NOTE - No check for sealing violations or
security is made unless a security manager is present.

IMPLEMENTATION NOTE - As of 8.0, this class loader implements InstrumentableClassLoader, permitting web application classes to instrument other classes in the same web application. It does not permit instrumentation of system or container classes or classes in other web apps. 
Author:
Remy Maucherat, Craig R. McClanahan/**
 * Specialized web application class loader.
 * <p>
 * This class loader is a full reimplementation of the
 * <code>URLClassLoader</code> from the JDK. It is designed to be fully
 * compatible with a normal <code>URLClassLoader</code>, although its internal
 * behavior may be completely different.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - By default, this class loader follows
 * the delegation model required by the specification. The system class
 * loader will be queried first, then the local repositories, and only then
 * delegation to the parent class loader will occur. This allows the web
 * application to override any shared class except the classes from J2SE.
 * Special handling is provided from the JAXP XML parser interfaces, the JNDI
 * interfaces, and the classes from the servlet API, which are never loaded
 * from the webapp repositories. The <code>delegate</code> property
 * allows an application to modify this behavior to move the parent class loader
 * ahead of the local repositories.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - Due to limitations in Jasper
 * compilation technology, any repository which contains classes from
 * the servlet API will be ignored by the class loader.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - The class loader generates source
 * URLs which include the full JAR URL when a class is loaded from a JAR file,
 * which allows setting security permission at the class level, even when a
 * class is contained inside a JAR.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - Local repositories are searched in
 * the order they are added via the initial constructor.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - No check for sealing violations or
 * security is made unless a security manager is present.
 * <p>
 * <strong>IMPLEMENTATION NOTE</strong> - As of 8.0, this class
 * loader implements {@link InstrumentableClassLoader}, permitting web
 * application classes to instrument other classes in the same web
 * application. It does not permit instrumentation of system or container
 * classes or classes in other web apps.
 *
 * @author Remy Maucherat
 * @author Craig R. McClanahan
 */
public abstract class WebappClassLoaderBase extends URLClassLoader
        implements Lifecycle, InstrumentableClassLoader, WebappProperties, PermissionCheck {

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

    
List of ThreadGroup names to ignore when scanning for web application
started threads that need to be shut down.
/**
     * List of ThreadGroup names to ignore when scanning for web application
     * started threads that need to be shut down.
     */
    private static final List<String> JVM_THREAD_GROUP_NAMES = new ArrayList<>();

    private static final String JVM_THREAD_GROUP_SYSTEM = "system";

    private static final String CLASS_FILE_SUFFIX = ".class";

    static {
        if (!JreCompat.isGraalAvailable()) {
            ClassLoader.registerAsParallelCapable();
        }
        JVM_THREAD_GROUP_NAMES.add(JVM_THREAD_GROUP_SYSTEM);
        JVM_THREAD_GROUP_NAMES.add("RMI Runtime");
    }

    protected class PrivilegedFindClassByName implements PrivilegedAction<Class<?>> {

        private final String name;

        PrivilegedFindClassByName(String name) {
            this.name = name;
        }

        @Override
        public Class<?> run() {
            return findClassInternal(name);
        }
    }


    protected static final class PrivilegedGetClassLoader implements PrivilegedAction<ClassLoader> {

        private final Class<?> clazz;

        public PrivilegedGetClassLoader(Class<?> clazz){
            this.clazz = clazz;
        }

        @Override
        public ClassLoader run() {
            return clazz.getClassLoader();
        }
    }


    protected final class PrivilegedJavaseGetResource implements PrivilegedAction<URL> {

        private final String name;

        public PrivilegedJavaseGetResource(String name) {
            this.name = name;
        }

        @Override
        public URL run() {
            return javaseClassLoader.getResource(name);
        }
    }


    // ------------------------------------------------------- Static Variables

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


    // ----------------------------------------------------------- Constructors

    
Construct a new ClassLoader with no defined repositories and no
parent ClassLoader.
/**
     * Construct a new ClassLoader with no defined repositories and no
     * parent ClassLoader.
     */
    protected WebappClassLoaderBase() {

        super(new URL[0]);

        ClassLoader p = getParent();
        if (p == null) {
            p = getSystemClassLoader();
        }
        this.parent = p;

        ClassLoader j = String.class.getClassLoader();
        if (j == null) {
            j = getSystemClassLoader();
            while (j.getParent() != null) {
                j = j.getParent();
            }
        }
        this.javaseClassLoader = j;

        securityManager = System.getSecurityManager();
        if (securityManager != null) {
            refreshPolicy();
        }
    }


    
Construct a new ClassLoader with no defined repositories and the given
parent ClassLoader.
 Method is used via reflection - see WebappLoader.createClassLoader() 
Params:
parent – Our parent class loader/**
     * Construct a new ClassLoader with no defined repositories and the given
     * parent ClassLoader.
     * <p>
     * Method is used via reflection -
     * see {@link WebappLoader#createClassLoader()}
     *
     * @param parent Our parent class loader
     */
    protected WebappClassLoaderBase(ClassLoader parent) {

        super(new URL[0], parent);

        ClassLoader p = getParent();
        if (p == null) {
            p = getSystemClassLoader();
        }
        this.parent = p;

        ClassLoader j = String.class.getClassLoader();
        if (j == null) {
            j = getSystemClassLoader();
            while (j.getParent() != null) {
                j = j.getParent();
            }
        }
        this.javaseClassLoader = j;

        securityManager = System.getSecurityManager();
        if (securityManager != null) {
            refreshPolicy();
        }
    }


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

    
Associated web resources for this webapp.
/**
     * Associated web resources for this webapp.
     */
    protected WebResourceRoot resources = null;


    
The cache of ResourceEntry for classes and resources we have loaded,
keyed by resource path, not binary name. Path is used as the key since
resources may be requested by binary name (classes) or path (other
resources such as property files) and the mapping from binary name to
path is unambiguous but the reverse mapping is ambiguous.
/**
     * The cache of ResourceEntry for classes and resources we have loaded,
     * keyed by resource path, not binary name. Path is used as the key since
     * resources may be requested by binary name (classes) or path (other
     * resources such as property files) and the mapping from binary name to
     * path is unambiguous but the reverse mapping is ambiguous.
     */
    protected final Map<String, ResourceEntry> resourceEntries =
            new ConcurrentHashMap<>();


    
Should this class loader delegate to the parent class loader
before searching its own repositories (i.e. the
usual Java2 delegation model)?  If set to false,
this class loader will search its own repositories first, and
delegate to the parent only if the class or resource is not
found locally. Note that the default, false, is
the behavior called for by the servlet specification.
/**
     * Should this class loader delegate to the parent class loader
     * <strong>before</strong> searching its own repositories (i.e. the
     * usual Java2 delegation model)?  If set to <code>false</code>,
     * this class loader will search its own repositories first, and
     * delegate to the parent only if the class or resource is not
     * found locally. Note that the default, <code>false</code>, is
     * the behavior called for by the servlet specification.
     */
    protected boolean delegate = false;


    private final Map<String,Long> jarModificationTimes = new HashMap<>();


    
A list of read File Permission's required if this loader is for a web
application context.
/**
     * A list of read File Permission's required if this loader is for a web
     * application context.
     */
    protected final ArrayList<Permission> permissionList = new ArrayList<>();


    
The PermissionCollection for each CodeSource for a web
application context.
/**
     * The PermissionCollection for each CodeSource for a web
     * application context.
     */
    protected final HashMap<String, PermissionCollection> loaderPC = new HashMap<>();


    
Instance of the SecurityManager installed.
/**
     * Instance of the SecurityManager installed.
     */
    protected final SecurityManager securityManager;


    
The parent class loader.
/**
     * The parent class loader.
     */
    protected final ClassLoader parent;


    
The bootstrap class loader used to load the JavaSE classes. In some
implementations this class loader is always null and in those cases ClassLoader.getParent() will be called recursively on the system class loader and the last non-null result used. /**
     * The bootstrap class loader used to load the JavaSE classes. In some
     * implementations this class loader is always <code>null</code> and in
     * those cases {@link ClassLoader#getParent()} will be called recursively on
     * the system class loader and the last non-null result used.
     */
    private ClassLoader javaseClassLoader;


    
Enables the RMI Target memory leak detection to be controlled. This is
necessary since the detection can only work on Java 9 if some of the
modularity checks are disabled.
/**
     * Enables the RMI Target memory leak detection to be controlled. This is
     * necessary since the detection can only work on Java 9 if some of the
     * modularity checks are disabled.
     */
    private boolean clearReferencesRmiTargets = true;

    
Should Tomcat attempt to terminate threads that have been started by the
web application? Stopping threads is performed via the deprecated (for
good reason) Thread.stop() method and is likely to result in
instability. As such, enabling this should be viewed as an option of last
resort in a development environment and is not recommended in a
production environment. If not specified, the default value of
false will be used.
/**
     * Should Tomcat attempt to terminate threads that have been started by the
     * web application? Stopping threads is performed via the deprecated (for
     * good reason) <code>Thread.stop()</code> method and is likely to result in
     * instability. As such, enabling this should be viewed as an option of last
     * resort in a development environment and is not recommended in a
     * production environment. If not specified, the default value of
     * <code>false</code> will be used.
     */
    private boolean clearReferencesStopThreads = false;

    
Should Tomcat attempt to terminate any TimerThreads that have been started by the web application? If not specified, the default value of false will be used.
/**
     * Should Tomcat attempt to terminate any {@link java.util.TimerThread}s
     * that have been started by the web application? If not specified, the
     * default value of <code>false</code> will be used.
     */
    private boolean clearReferencesStopTimerThreads = false;

    
Should Tomcat call LogFactory.release(ClassLoader) when the class loader is stopped? If not specified, the default value of true is used. Changing the default setting is likely to
lead to memory leaks and other issues.
/**
     * Should Tomcat call
     * {@link org.apache.juli.logging.LogFactory#release(ClassLoader)}
     * when the class loader is stopped? If not specified, the default value
     * of <code>true</code> is used. Changing the default setting is likely to
     * lead to memory leaks and other issues.
     */
    private boolean clearReferencesLogFactoryRelease = true;

    
If an HttpClient keep-alive timer thread has been started by this web application and is still running, should Tomcat change the context class loader from the current ClassLoader to ClassLoader.getParent() to prevent a memory leak? Note that the keep-alive timer thread will stop on its own once the keep-alives all expire however, on a busy system that might not happen for some time. /**
     * If an HttpClient keep-alive timer thread has been started by this web
     * application and is still running, should Tomcat change the context class
     * loader from the current {@link ClassLoader} to
     * {@link ClassLoader#getParent()} to prevent a memory leak? Note that the
     * keep-alive timer thread will stop on its own once the keep-alives all
     * expire however, on a busy system that might not happen for some time.
     */
    private boolean clearReferencesHttpClientKeepAliveThread = true;

    
Should Tomcat attempt to clear references to classes loaded by this class
loader from the ObjectStreamClass caches?
/**
     * Should Tomcat attempt to clear references to classes loaded by this class
     * loader from the ObjectStreamClass caches?
     */
    private boolean clearReferencesObjectStreamClassCaches = true;

    
Should Tomcat attempt to clear references to classes loaded by this class
loader from ThreadLocals?
/**
     * Should Tomcat attempt to clear references to classes loaded by this class
     * loader from ThreadLocals?
     */
    private boolean clearReferencesThreadLocals = true;

    
Should Tomcat skip the memory leak checks when the web application is
stopped as part of the process of shutting down the JVM?
/**
     * Should Tomcat skip the memory leak checks when the web application is
     * stopped as part of the process of shutting down the JVM?
     */
    private boolean skipMemoryLeakChecksOnJvmShutdown = false;

    
Holds the class file transformers decorating this class loader. The
CopyOnWriteArrayList is thread safe. It is expensive on writes, but
those should be rare. It is very fast on reads, since synchronization
is not actually used. Importantly, the ClassLoader will never block
iterating over the transformers while loading a class.
/**
     * Holds the class file transformers decorating this class loader. The
     * CopyOnWriteArrayList is thread safe. It is expensive on writes, but
     * those should be rare. It is very fast on reads, since synchronization
     * is not actually used. Importantly, the ClassLoader will never block
     * iterating over the transformers while loading a class.
     */
    private final List<ClassFileTransformer> transformers = new CopyOnWriteArrayList<>();


    
Flag that indicates that addURL(URL) has been called which creates a requirement to check the super class when searching for resources. /**
     * Flag that indicates that {@link #addURL(URL)} has been called which
     * creates a requirement to check the super class when searching for
     * resources.
     */
    private boolean hasExternalRepositories = false;


    
Repositories managed by this class rather than the super class.
/**
     * Repositories managed by this class rather than the super class.
     */
    private List<URL> localRepositories = new ArrayList<>();


    private volatile LifecycleState state = LifecycleState.NEW;


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

    
Returns:
associated resources./**
     * @return associated resources.
     */
    public WebResourceRoot getResources() {
        return this.resources;
    }


    
Set associated resources.
Params:
resources – the resources from which the classloader will
    load the classes/**
     * Set associated resources.
     * @param resources the resources from which the classloader will
     *     load the classes
     */
    public void setResources(WebResourceRoot resources) {
        this.resources = resources;
    }


    
Returns:
the context name for this class loader./**
     * @return the context name for this class loader.
     */
    public String getContextName() {
        if (resources == null) {
            return "Unknown";
        } else {
            return resources.getContext().getBaseName();
        }
    }


    
Return the "delegate first" flag for this class loader.
Returns:
true if the class lookup will delegate to
  the parent first. The default in Tomcat is false./**
     * Return the "delegate first" flag for this class loader.
     * @return <code>true</code> if the class lookup will delegate to
     *   the parent first. The default in Tomcat is <code>false</code>.
     */
    public boolean getDelegate() {
        return this.delegate;
    }


    
Set the "delegate first" flag for this class loader.
If this flag is true, this class loader delegates
to the parent class loader
before searching its own repositories, as
in an ordinary (non-servlet) chain of Java class loaders.
If set to false (the default),
this class loader will search its own repositories first, and
delegate to the parent only if the class or resource is not
found locally, as per the servlet specification.
Params:
delegate – The new "delegate first" flag/**
     * Set the "delegate first" flag for this class loader.
     * If this flag is true, this class loader delegates
     * to the parent class loader
     * <strong>before</strong> searching its own repositories, as
     * in an ordinary (non-servlet) chain of Java class loaders.
     * If set to <code>false</code> (the default),
     * this class loader will search its own repositories first, and
     * delegate to the parent only if the class or resource is not
     * found locally, as per the servlet specification.
     *
     * @param delegate The new "delegate first" flag
     */
    public void setDelegate(boolean delegate) {
        this.delegate = delegate;
    }


    
If there is a Java SecurityManager create a read permission for the
target of the given URL as appropriate.
Params:
url – URL for a file or directory on local system/**
     * If there is a Java SecurityManager create a read permission for the
     * target of the given URL as appropriate.
     *
     * @param url URL for a file or directory on local system
     */
    void addPermission(URL url) {
        if (url == null) {
            return;
        }
        if (securityManager != null) {
            String protocol = url.getProtocol();
            if ("file".equalsIgnoreCase(protocol)) {
                URI uri;
                File f;
                String path;
                try {
                    uri = url.toURI();
                    f = new File(uri);
                    path = f.getCanonicalPath();
                } catch (IOException | URISyntaxException e) {
                    log.warn(sm.getString(
                            "webappClassLoader.addPermissionNoCanonicalFile",
                            url.toExternalForm()));
                    return;
                }
                if (f.isFile()) {
                    // Allow the file to be read
                    addPermission(new FilePermission(path, "read"));
                } else if (f.isDirectory()) {
                    addPermission(new FilePermission(path, "read"));
                    addPermission(new FilePermission(
                            path + File.separator + "-", "read"));
                } else {
                    // File does not exist - ignore (shouldn't happen)
                }
            } else {
                // Unsupported URL protocol
                log.warn(sm.getString(
                        "webappClassLoader.addPermissionNoProtocol",
                        protocol, url.toExternalForm()));
            }
        }
    }


    
If there is a Java SecurityManager create a Permission.
Params:
permission – The permission/**
     * If there is a Java SecurityManager create a Permission.
     *
     * @param permission The permission
     */
    void addPermission(Permission permission) {
        if ((securityManager != null) && (permission != null)) {
            permissionList.add(permission);
        }
    }


    public boolean getClearReferencesRmiTargets() {
        return this.clearReferencesRmiTargets;
    }


    public void setClearReferencesRmiTargets(boolean clearReferencesRmiTargets) {
        this.clearReferencesRmiTargets = clearReferencesRmiTargets;
    }


    
Returns:
the clearReferencesStopThreads flag for this Context./**
     * @return the clearReferencesStopThreads flag for this Context.
     */
    public boolean getClearReferencesStopThreads() {
        return this.clearReferencesStopThreads;
    }


    
Set the clearReferencesStopThreads feature for this Context.
Params:
clearReferencesStopThreads – The new flag value/**
     * Set the clearReferencesStopThreads feature for this Context.
     *
     * @param clearReferencesStopThreads The new flag value
     */
    public void setClearReferencesStopThreads(
            boolean clearReferencesStopThreads) {
        this.clearReferencesStopThreads = clearReferencesStopThreads;
    }


    
Returns:
the clearReferencesStopTimerThreads flag for this Context./**
     * @return the clearReferencesStopTimerThreads flag for this Context.
     */
    public boolean getClearReferencesStopTimerThreads() {
        return this.clearReferencesStopTimerThreads;
    }


    
Set the clearReferencesStopTimerThreads feature for this Context.
Params:
clearReferencesStopTimerThreads – The new flag value/**
     * Set the clearReferencesStopTimerThreads feature for this Context.
     *
     * @param clearReferencesStopTimerThreads The new flag value
     */
    public void setClearReferencesStopTimerThreads(
            boolean clearReferencesStopTimerThreads) {
        this.clearReferencesStopTimerThreads = clearReferencesStopTimerThreads;
    }


    
Returns:
the clearReferencesLogFactoryRelease flag for this Context./**
     * @return the clearReferencesLogFactoryRelease flag for this Context.
     */
    public boolean getClearReferencesLogFactoryRelease() {
        return this.clearReferencesLogFactoryRelease;
    }


    
Set the clearReferencesLogFactoryRelease feature for this Context.
Params:
clearReferencesLogFactoryRelease – The new flag value/**
     * Set the clearReferencesLogFactoryRelease feature for this Context.
     *
     * @param clearReferencesLogFactoryRelease The new flag value
     */
    public void setClearReferencesLogFactoryRelease(
            boolean clearReferencesLogFactoryRelease) {
        this.clearReferencesLogFactoryRelease =
            clearReferencesLogFactoryRelease;
    }


    
Returns:
the clearReferencesHttpClientKeepAliveThread flag for this
Context./**
     * @return the clearReferencesHttpClientKeepAliveThread flag for this
     * Context.
     */
    public boolean getClearReferencesHttpClientKeepAliveThread() {
        return this.clearReferencesHttpClientKeepAliveThread;
    }


    
Set the clearReferencesHttpClientKeepAliveThread feature for this
Context.
Params:
clearReferencesHttpClientKeepAliveThread – The new flag value/**
     * Set the clearReferencesHttpClientKeepAliveThread feature for this
     * Context.
     *
     * @param clearReferencesHttpClientKeepAliveThread The new flag value
     */
    public void setClearReferencesHttpClientKeepAliveThread(
            boolean clearReferencesHttpClientKeepAliveThread) {
        this.clearReferencesHttpClientKeepAliveThread =
            clearReferencesHttpClientKeepAliveThread;
    }


    public boolean getClearReferencesObjectStreamClassCaches() {
        return clearReferencesObjectStreamClassCaches;
    }


    public void setClearReferencesObjectStreamClassCaches(
            boolean clearReferencesObjectStreamClassCaches) {
        this.clearReferencesObjectStreamClassCaches = clearReferencesObjectStreamClassCaches;
    }


    public boolean getClearReferencesThreadLocals() {
        return clearReferencesThreadLocals;
    }


    public void setClearReferencesThreadLocals(boolean clearReferencesThreadLocals) {
        this.clearReferencesThreadLocals = clearReferencesThreadLocals;
    }


    public boolean getSkipMemoryLeakChecksOnJvmShutdown() {
        return skipMemoryLeakChecksOnJvmShutdown;
    }


    public void setSkipMemoryLeakChecksOnJvmShutdown(boolean skipMemoryLeakChecksOnJvmShutdown) {
        this.skipMemoryLeakChecksOnJvmShutdown = skipMemoryLeakChecksOnJvmShutdown;
    }


    // ------------------------------------------------------- Reloader Methods

    
Adds the specified class file transformer to this class loader. The
transformer will then be able to modify the bytecode of any classes
loaded by this class loader after the invocation of this method.
Params:
transformer – The transformer to add to the class loader/**
     * Adds the specified class file transformer to this class loader. The
     * transformer will then be able to modify the bytecode of any classes
     * loaded by this class loader after the invocation of this method.
     *
     * @param transformer The transformer to add to the class loader
     */
    @Override
    public void addTransformer(ClassFileTransformer transformer) {

        if (transformer == null) {
            throw new IllegalArgumentException(sm.getString(
                    "webappClassLoader.addTransformer.illegalArgument", getContextName()));
        }

        if (this.transformers.contains(transformer)) {
            // if the same instance of this transformer was already added, bail out
            log.warn(sm.getString("webappClassLoader.addTransformer.duplicate",
                    transformer, getContextName()));
            return;
        }
        this.transformers.add(transformer);

        log.info(sm.getString("webappClassLoader.addTransformer", transformer, getContextName()));
    }

    
Removes the specified class file transformer from this class loader.
It will no longer be able to modify the byte code of any classes
loaded by the class loader after the invocation of this method.
However, any classes already modified by this transformer will
remain transformed.
Params:
transformer – The transformer to remove/**
     * Removes the specified class file transformer from this class loader.
     * It will no longer be able to modify the byte code of any classes
     * loaded by the class loader after the invocation of this method.
     * However, any classes already modified by this transformer will
     * remain transformed.
     *
     * @param transformer The transformer to remove
     */
    @Override
    public void removeTransformer(ClassFileTransformer transformer) {

        if (transformer == null) {
            return;
        }

        if (this.transformers.remove(transformer)) {
            log.info(sm.getString("webappClassLoader.removeTransformer",
                    transformer, getContextName()));
        }
    }

    protected void copyStateWithoutTransformers(WebappClassLoaderBase base) {
        base.resources = this.resources;
        base.delegate = this.delegate;
        base.state = LifecycleState.NEW;
        base.clearReferencesStopThreads = this.clearReferencesStopThreads;
        base.clearReferencesStopTimerThreads = this.clearReferencesStopTimerThreads;
        base.clearReferencesLogFactoryRelease = this.clearReferencesLogFactoryRelease;
        base.clearReferencesHttpClientKeepAliveThread = this.clearReferencesHttpClientKeepAliveThread;
        base.jarModificationTimes.putAll(this.jarModificationTimes);
        base.permissionList.addAll(this.permissionList);
        base.loaderPC.putAll(this.loaderPC);
    }

    
Have one or more classes or resources been modified so that a reload
is appropriate?
Returns:
true if there's been a modification/**
     * Have one or more classes or resources been modified so that a reload
     * is appropriate?
     * @return <code>true</code> if there's been a modification
     */
    public boolean modified() {

        if (log.isDebugEnabled())
            log.debug("modified()");

        for (Entry<String,ResourceEntry> entry : resourceEntries.entrySet()) {
            long cachedLastModified = entry.getValue().lastModified;
            long lastModified = resources.getClassLoaderResource(
                    entry.getKey()).getLastModified();
            if (lastModified != cachedLastModified) {
                if( log.isDebugEnabled() )
                    log.debug(sm.getString("webappClassLoader.resourceModified",
                            entry.getKey(),
                            new Date(cachedLastModified),
                            new Date(lastModified)));
                return true;
            }
        }

        // Check if JARs have been added or removed
        WebResource[] jars = resources.listResources("/WEB-INF/lib");
        // Filter out non-JAR resources

        int jarCount = 0;
        for (WebResource jar : jars) {
            if (jar.getName().endsWith(".jar") && jar.isFile() && jar.canRead()) {
                jarCount++;
                Long recordedLastModified = jarModificationTimes.get(jar.getName());
                if (recordedLastModified == null) {
                    // Jar has been added
                    log.info(sm.getString("webappClassLoader.jarsAdded",
                            resources.getContext().getName()));
                    return true;
                }
                if (recordedLastModified.longValue() != jar.getLastModified()) {
                    // Jar has been changed
                    log.info(sm.getString("webappClassLoader.jarsModified",
                            resources.getContext().getName()));
                    return true;
                }
            }
        }

        if (jarCount < jarModificationTimes.size()){
            log.info(sm.getString("webappClassLoader.jarsRemoved",
                    resources.getContext().getName()));
            return true;
        }


        // No classes have been modified
        return false;
    }


    @Override
    public String toString() {

        StringBuilder sb = new StringBuilder(this.getClass().getSimpleName());
        sb.append("\r\n  context: ");
        sb.append(getContextName());
        sb.append("\r\n  delegate: ");
        sb.append(delegate);
        sb.append("\r\n");
        if (this.parent != null) {
            sb.append("----------> Parent Classloader:\r\n");
            sb.append(this.parent.toString());
            sb.append("\r\n");
        }
        if (this.transformers.size() > 0) {
            sb.append("----------> Class file transformers:\r\n");
            for (ClassFileTransformer transformer : this.transformers) {
                sb.append(transformer).append("\r\n");
            }
        }
        return sb.toString();
    }


    // ---------------------------------------------------- ClassLoader Methods


    // Note: exposed for use by tests
    protected final Class<?> doDefineClass(String name, byte[] b, int off, int len,
            ProtectionDomain protectionDomain) {
        return super.defineClass(name, b, off, len, protectionDomain);
    }

    
Find the specified class in our local repositories, if possible.  If
not found, throw ClassNotFoundException.
Params:
name – The binary name of the class to be loaded
Throws:
ClassNotFoundException – if the class was not found/**
     * Find the specified class in our local repositories, if possible.  If
     * not found, throw <code>ClassNotFoundException</code>.
     *
     * @param name The binary name of the class to be loaded
     *
     * @exception ClassNotFoundException if the class was not found
     */
    @Override
    public Class<?> findClass(String name) throws ClassNotFoundException {

        if (log.isDebugEnabled())
            log.debug("    findClass(" + name + ")");

        checkStateForClassLoading(name);

        // (1) Permission to define this class when using a SecurityManager
        if (securityManager != null) {
            int i = name.lastIndexOf('.');
            if (i >= 0) {
                try {
                    if (log.isTraceEnabled())
                        log.trace("      securityManager.checkPackageDefinition");
                    securityManager.checkPackageDefinition(name.substring(0,i));
                } catch (Exception se) {
                    if (log.isTraceEnabled())
                        log.trace("      -->Exception-->ClassNotFoundException", se);
                    throw new ClassNotFoundException(name, se);
                }
            }
        }

        // Ask our superclass to locate this class, if possible
        // (throws ClassNotFoundException if it is not found)
        Class<?> clazz = null;
        try {
            if (log.isTraceEnabled())
                log.trace("      findClassInternal(" + name + ")");
            try {
                if (securityManager != null) {
                    PrivilegedAction<Class<?>> dp =
                        new PrivilegedFindClassByName(name);
                    clazz = AccessController.doPrivileged(dp);
                } else {
                    clazz = findClassInternal(name);
                }
            } catch(AccessControlException ace) {
                log.warn(sm.getString("webappClassLoader.securityException", name,
                        ace.getMessage()), ace);
                throw new ClassNotFoundException(name, ace);
            } catch (RuntimeException e) {
                if (log.isTraceEnabled())
                    log.trace("      -->RuntimeException Rethrown", e);
                throw e;
            }
            if ((clazz == null) && hasExternalRepositories) {
                try {
                    clazz = super.findClass(name);
                } catch(AccessControlException ace) {
                    log.warn(sm.getString("webappClassLoader.securityException", name,
                            ace.getMessage()), ace);
                    throw new ClassNotFoundException(name, ace);
                } catch (RuntimeException e) {
                    if (log.isTraceEnabled())
                        log.trace("      -->RuntimeException Rethrown", e);
                    throw e;
                }
            }
            if (clazz == null) {
                if (log.isDebugEnabled())
                    log.debug("    --> Returning ClassNotFoundException");
                throw new ClassNotFoundException(name);
            }
        } catch (ClassNotFoundException e) {
            if (log.isTraceEnabled())
                log.trace("    --> Passing on ClassNotFoundException");
            throw e;
        }

        // Return the class we have located
        if (log.isTraceEnabled())
            log.debug("      Returning class " + clazz);

        if (log.isTraceEnabled()) {
            ClassLoader cl;
            if (Globals.IS_SECURITY_ENABLED){
                cl = AccessController.doPrivileged(
                    new PrivilegedGetClassLoader(clazz));
            } else {
                cl = clazz.getClassLoader();
            }
            log.debug("      Loaded by " + cl.toString());
        }
        return clazz;

    }


    
Find the specified resource in our local repository, and return a
URL referring to it, or null if this resource
cannot be found.
Params:
name – Name of the resource to be found/**
     * Find the specified resource in our local repository, and return a
     * <code>URL</code> referring to it, or <code>null</code> if this resource
     * cannot be found.
     *
     * @param name Name of the resource to be found
     */
    @Override
    public URL findResource(final String name) {

        if (log.isDebugEnabled())
            log.debug("    findResource(" + name + ")");

        checkStateForResourceLoading(name);

        URL url = null;

        String path = nameToPath(name);

        WebResource resource = resources.getClassLoaderResource(path);
        if (resource.exists()) {
            url = resource.getURL();
            trackLastModified(path, resource);
        }

        if ((url == null) && hasExternalRepositories) {
            url = super.findResource(name);
        }

        if (log.isDebugEnabled()) {
            if (url != null)
                log.debug("    --> Returning '" + url.toString() + "'");
            else
                log.debug("    --> Resource not found, returning null");
        }
        return url;
    }


    private void trackLastModified(String path, WebResource resource) {
        if (resourceEntries.containsKey(path)) {
            return;
        }
        ResourceEntry entry = new ResourceEntry();
        entry.lastModified = resource.getLastModified();
        synchronized(resourceEntries) {
            resourceEntries.putIfAbsent(path, entry);
        }
    }


    
Return an enumeration of URLs representing all of the
resources with the given name.  If no resources with this name are
found, return an empty enumeration.
Params:
name – Name of the resources to be found
Throws:
IOException – if an input/output error occurs/**
     * Return an enumeration of <code>URLs</code> representing all of the
     * resources with the given name.  If no resources with this name are
     * found, return an empty enumeration.
     *
     * @param name Name of the resources to be found
     *
     * @exception IOException if an input/output error occurs
     */
    @Override
    public Enumeration<URL> findResources(String name) throws IOException {

        if (log.isDebugEnabled())
            log.debug("    findResources(" + name + ")");

        checkStateForResourceLoading(name);

        LinkedHashSet<URL> result = new LinkedHashSet<>();

        String path = nameToPath(name);

        WebResource[] webResources = resources.getClassLoaderResources(path);
        for (WebResource webResource : webResources) {
            if (webResource.exists()) {
                result.add(webResource.getURL());
            }
        }

        // Adding the results of a call to the superclass
        if (hasExternalRepositories) {
            Enumeration<URL> otherResourcePaths = super.findResources(name);
            while (otherResourcePaths.hasMoreElements()) {
                result.add(otherResourcePaths.nextElement());
            }
        }

        return Collections.enumeration(result);
    }


    
Find the resource with the given name.  A resource is some data
(images, audio, text, etc.) that can be accessed by class code in a
way that is independent of the location of the code.  The name of a
resource is a "/"-separated path name that identifies the resource.
If the resource cannot be found, return null.

This method searches according to the following algorithm, returning
as soon as it finds the appropriate URL.  If the resource cannot be
found, returns null.

If the delegate property is set to true,
    call the getResource() method of the parent class
    loader, if any.
Call findResource() to find this resource in our
    locally defined repositories.
Call the getResource() method of the parent class
    loader, if any.

Params:
name – Name of the resource to return a URL for/**
     * Find the resource with the given name.  A resource is some data
     * (images, audio, text, etc.) that can be accessed by class code in a
     * way that is independent of the location of the code.  The name of a
     * resource is a "/"-separated path name that identifies the resource.
     * If the resource cannot be found, return <code>null</code>.
     * <p>
     * This method searches according to the following algorithm, returning
     * as soon as it finds the appropriate URL.  If the resource cannot be
     * found, returns <code>null</code>.
     * <ul>
     * <li>If the <code>delegate</code> property is set to <code>true</code>,
     *     call the <code>getResource()</code> method of the parent class
     *     loader, if any.</li>
     * <li>Call <code>findResource()</code> to find this resource in our
     *     locally defined repositories.</li>
     * <li>Call the <code>getResource()</code> method of the parent class
     *     loader, if any.</li>
     * </ul>
     *
     * @param name Name of the resource to return a URL for
     */
    @Override
    public URL getResource(String name) {

        if (log.isDebugEnabled())
            log.debug("getResource(" + name + ")");

        checkStateForResourceLoading(name);

        URL url = null;

        boolean delegateFirst = delegate || filter(name, false);

        // (1) Delegate to parent if requested
        if (delegateFirst) {
            if (log.isDebugEnabled())
                log.debug("  Delegating to parent classloader " + parent);
            url = parent.getResource(name);
            if (url != null) {
                if (log.isDebugEnabled())
                    log.debug("  --> Returning '" + url.toString() + "'");
                return url;
            }
        }

        // (2) Search local repositories
        url = findResource(name);
        if (url != null) {
            if (log.isDebugEnabled())
                log.debug("  --> Returning '" + url.toString() + "'");
            return url;
        }

        // (3) Delegate to parent unconditionally if not already attempted
        if (!delegateFirst) {
            url = parent.getResource(name);
            if (url != null) {
                if (log.isDebugEnabled())
                    log.debug("  --> Returning '" + url.toString() + "'");
                return url;
            }
        }

        // (4) Resource was not found
        if (log.isDebugEnabled())
            log.debug("  --> Resource not found, returning null");
        return null;

    }


    @Override
    public Enumeration<URL> getResources(String name) throws IOException {

        Enumeration<URL> parentResources = getParent().getResources(name);
        Enumeration<URL> localResources = findResources(name);

        // Need to combine these enumerations. The order in which the
        // Enumerations are combined depends on how delegation is configured
        boolean delegateFirst = delegate || filter(name, false);

        if (delegateFirst) {
            return new CombinedEnumeration(parentResources, localResources);
        } else {
            return new CombinedEnumeration(localResources, parentResources);
        }
    }


    
Find the resource with the given name, and return an input stream
that can be used for reading it.  The search order is as described
for getResource(), after checking to see if the resource
data has been previously cached.  If the resource cannot be found,
return null.
Params:
name – Name of the resource to return an input stream for/**
     * Find the resource with the given name, and return an input stream
     * that can be used for reading it.  The search order is as described
     * for <code>getResource()</code>, after checking to see if the resource
     * data has been previously cached.  If the resource cannot be found,
     * return <code>null</code>.
     *
     * @param name Name of the resource to return an input stream for
     */
    @Override
    public InputStream getResourceAsStream(String name) {

        if (log.isDebugEnabled())
            log.debug("getResourceAsStream(" + name + ")");

        checkStateForResourceLoading(name);

        InputStream stream = null;

        boolean delegateFirst = delegate || filter(name, false);

        // (1) Delegate to parent if requested
        if (delegateFirst) {
            if (log.isDebugEnabled())
                log.debug("  Delegating to parent classloader " + parent);
            stream = parent.getResourceAsStream(name);
            if (stream != null) {
                if (log.isDebugEnabled())
                    log.debug("  --> Returning stream from parent");
                return stream;
            }
        }

        // (2) Search local repositories
        if (log.isDebugEnabled())
            log.debug("  Searching local repositories");
        String path = nameToPath(name);
        WebResource resource = resources.getClassLoaderResource(path);
        if (resource.exists()) {
            stream = resource.getInputStream();
            trackLastModified(path, resource);
        }
        try {
            if (hasExternalRepositories && stream == null) {
                URL url = super.findResource(name);
                if (url != null) {
                    stream = url.openStream();
                }
            }
        } catch (IOException e) {
            // Ignore
        }
        if (stream != null) {
            if (log.isDebugEnabled())
                log.debug("  --> Returning stream from local");
            return stream;
        }

        // (3) Delegate to parent unconditionally
        if (!delegateFirst) {
            if (log.isDebugEnabled())
                log.debug("  Delegating to parent classloader unconditionally " + parent);
            stream = parent.getResourceAsStream(name);
            if (stream != null) {
                if (log.isDebugEnabled())
                    log.debug("  --> Returning stream from parent");
                return stream;
            }
        }

        // (4) Resource was not found
        if (log.isDebugEnabled())
            log.debug("  --> Resource not found, returning null");
        return null;
    }


    
Load the class with the specified name.  This method searches for
classes in the same manner as loadClass(String, boolean)
with false as the second argument.
Params:
name – The binary name of the class to be loaded
Throws:
ClassNotFoundException – if the class was not found/**
     * Load the class with the specified name.  This method searches for
     * classes in the same manner as <code>loadClass(String, boolean)</code>
     * with <code>false</code> as the second argument.
     *
     * @param name The binary name of the class to be loaded
     *
     * @exception ClassNotFoundException if the class was not found
     */
    @Override
    public Class<?> loadClass(String name) throws ClassNotFoundException {
        return loadClass(name, false);
    }


    
Load the class with the specified name, searching using the following
algorithm until it finds and returns the class.  If the class cannot
be found, returns ClassNotFoundException.

Call findLoadedClass(String) to check if the
    class has already been loaded.  If it has, the same
    Class object is returned.
If the delegate property is set to true,
    call the loadClass() method of the parent class
    loader, if any.
Call findClass() to find this class in our locally
    defined repositories.
Call the loadClass() method of our parent
    class loader, if any.

If the class was found using the above steps, and the
resolve flag is true, this method will then
call resolveClass(Class) on the resulting Class object.
Params:
name – The binary name of the class to be loaded
resolve – If true then resolve the class
Throws:
ClassNotFoundException – if the class was not found/**
     * Load the class with the specified name, searching using the following
     * algorithm until it finds and returns the class.  If the class cannot
     * be found, returns <code>ClassNotFoundException</code>.
     * <ul>
     * <li>Call <code>findLoadedClass(String)</code> to check if the
     *     class has already been loaded.  If it has, the same
     *     <code>Class</code> object is returned.</li>
     * <li>If the <code>delegate</code> property is set to <code>true</code>,
     *     call the <code>loadClass()</code> method of the parent class
     *     loader, if any.</li>
     * <li>Call <code>findClass()</code> to find this class in our locally
     *     defined repositories.</li>
     * <li>Call the <code>loadClass()</code> method of our parent
     *     class loader, if any.</li>
     * </ul>
     * If the class was found using the above steps, and the
     * <code>resolve</code> flag is <code>true</code>, this method will then
     * call <code>resolveClass(Class)</code> on the resulting Class object.
     *
     * @param name The binary name of the class to be loaded
     * @param resolve If <code>true</code> then resolve the class
     *
     * @exception ClassNotFoundException if the class was not found
     */
    @Override
    public Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {

        synchronized (JreCompat.isGraalAvailable() ? this : getClassLoadingLock(name)) {
            if (log.isDebugEnabled())
                log.debug("loadClass(" + name + ", " + resolve + ")");
            Class<?> clazz = null;

            // Log access to stopped class loader
            checkStateForClassLoading(name);

            // (0) Check our previously loaded local class cache
            clazz = findLoadedClass0(name);
            if (clazz != null) {
                if (log.isDebugEnabled())
                    log.debug("  Returning class from cache");
                if (resolve)
                    resolveClass(clazz);
                return clazz;
            }

            // (0.1) Check our previously loaded class cache
            clazz = JreCompat.isGraalAvailable() ? null : findLoadedClass(name);
            if (clazz != null) {
                if (log.isDebugEnabled())
                    log.debug("  Returning class from cache");
                if (resolve)
                    resolveClass(clazz);
                return clazz;
            }

            // (0.2) Try loading the class with the system class loader, to prevent
            //       the webapp from overriding Java SE classes. This implements
            //       SRV.10.7.2
            String resourceName = binaryNameToPath(name, false);

            ClassLoader javaseLoader = getJavaseClassLoader();
            boolean tryLoadingFromJavaseLoader;
            try {
                // Use getResource as it won't trigger an expensive
                // ClassNotFoundException if the resource is not available from
                // the Java SE class loader. However (see
                // https://bz.apache.org/bugzilla/show_bug.cgi?id=58125 for
                // details) when running under a security manager in rare cases
                // this call may trigger a ClassCircularityError.
                // See https://bz.apache.org/bugzilla/show_bug.cgi?id=61424 for
                // details of how this may trigger a StackOverflowError
                // Given these reported errors, catch Throwable to ensure any
                // other edge cases are also caught
                URL url;
                if (securityManager != null) {
                    PrivilegedAction<URL> dp = new PrivilegedJavaseGetResource(resourceName);
                    url = AccessController.doPrivileged(dp);
                } else {
                    url = javaseLoader.getResource(resourceName);
                }
                tryLoadingFromJavaseLoader = (url != null);
            } catch (Throwable t) {
                // Swallow all exceptions apart from those that must be re-thrown
                ExceptionUtils.handleThrowable(t);
                // The getResource() trick won't work for this class. We have to
                // try loading it directly and accept that we might get a
                // ClassNotFoundException.
                tryLoadingFromJavaseLoader = true;
            }

            if (tryLoadingFromJavaseLoader) {
                try {
                    clazz = javaseLoader.loadClass(name);
                    if (clazz != null) {
                        if (resolve)
                            resolveClass(clazz);
                        return clazz;
                    }
                } catch (ClassNotFoundException e) {
                    // Ignore
                }
            }

            // (0.5) Permission to access this class when using a SecurityManager
            if (securityManager != null) {
                int i = name.lastIndexOf('.');
                if (i >= 0) {
                    try {
                        securityManager.checkPackageAccess(name.substring(0,i));
                    } catch (SecurityException se) {
                        String error = sm.getString("webappClassLoader.restrictedPackage", name);
                        log.info(error, se);
                        throw new ClassNotFoundException(error, se);
                    }
                }
            }

            boolean delegateLoad = delegate || filter(name, true);

            // (1) Delegate to our parent if requested
            if (delegateLoad) {
                if (log.isDebugEnabled())
                    log.debug("  Delegating to parent classloader1 " + parent);
                try {
                    clazz = Class.forName(name, false, parent);
                    if (clazz != null) {
                        if (log.isDebugEnabled())
                            log.debug("  Loading class from parent");
                        if (resolve)
                            resolveClass(clazz);
                        return clazz;
                    }
                } catch (ClassNotFoundException e) {
                    // Ignore
                }
            }

            // (2) Search local repositories
            if (log.isDebugEnabled())
                log.debug("  Searching local repositories");
            try {
                clazz = findClass(name);
                if (clazz != null) {
                    if (log.isDebugEnabled())
                        log.debug("  Loading class from local repository");
                    if (resolve)
                        resolveClass(clazz);
                    return clazz;
                }
            } catch (ClassNotFoundException e) {
                // Ignore
            }

            // (3) Delegate to parent unconditionally
            if (!delegateLoad) {
                if (log.isDebugEnabled())
                    log.debug("  Delegating to parent classloader at end: " + parent);
                try {
                    clazz = Class.forName(name, false, parent);
                    if (clazz != null) {
                        if (log.isDebugEnabled())
                            log.debug("  Loading class from parent");
                        if (resolve)
                            resolveClass(clazz);
                        return clazz;
                    }
                } catch (ClassNotFoundException e) {
                    // Ignore
                }
            }
        }

        throw new ClassNotFoundException(name);
    }


    protected void checkStateForClassLoading(String className) throws ClassNotFoundException {
        // It is not permitted to load new classes once the web application has
        // been stopped.
        try {
            checkStateForResourceLoading(className);
        } catch (IllegalStateException ise) {
            throw new ClassNotFoundException(ise.getMessage(), ise);
        }
    }


    protected void checkStateForResourceLoading(String resource) throws IllegalStateException {
        // It is not permitted to load resources once the web application has
        // been stopped.
        if (!state.isAvailable()) {
            String msg = sm.getString("webappClassLoader.stopped", resource);
            IllegalStateException ise = new IllegalStateException(msg);
            log.info(msg, ise);
            throw ise;
        }
    }

    
Get the Permissions for a CodeSource.  If this instance
of WebappClassLoaderBase is for a web application context,
add read FilePermission for the appropriate resources.
Params:
codeSource – where the code was loaded from
Returns:
PermissionCollection for CodeSource/**
     * Get the Permissions for a CodeSource.  If this instance
     * of WebappClassLoaderBase is for a web application context,
     * add read FilePermission for the appropriate resources.
     *
     * @param codeSource where the code was loaded from
     * @return PermissionCollection for CodeSource
     */
    @Override
    protected PermissionCollection getPermissions(CodeSource codeSource) {
        String codeUrl = codeSource.getLocation().toString();
        PermissionCollection pc;
        if ((pc = loaderPC.get(codeUrl)) == null) {
            pc = super.getPermissions(codeSource);
            if (pc != null) {
                for (Permission p : permissionList) {
                    pc.add(p);
                }
                loaderPC.put(codeUrl,pc);
            }
        }
        return pc;
    }


    @Override
    public boolean check(Permission permission) {
        if (!Globals.IS_SECURITY_ENABLED) {
            return true;
        }
        Policy currentPolicy = Policy.getPolicy();
        if (currentPolicy != null) {
            URL contextRootUrl = resources.getResource("/").getCodeBase();
            CodeSource cs = new CodeSource(contextRootUrl, (Certificate[]) null);
            PermissionCollection pc = currentPolicy.getPermissions(cs);
            if (pc.implies(permission)) {
                return true;
            }
        }
        return false;
    }


    
{@inheritDoc}
 Note that list of URLs returned by this method may not be complete. The web application class loader accesses class loader resources via the WebResourceRoot which supports the arbitrary mapping of additional files, directories and contents of JAR files under WEB-INF/classes. Any such resources will not be included in the URLs returned here. /**
     * {@inheritDoc}
     * <p>
     * Note that list of URLs returned by this method may not be complete. The
     * web application class loader accesses class loader resources via the
     * {@link WebResourceRoot} which supports the arbitrary mapping of
     * additional files, directories and contents of JAR files under
     * WEB-INF/classes. Any such resources will not be included in the URLs
     * returned here.
     */
    @Override
    public URL[] getURLs() {
        ArrayList<URL> result = new ArrayList<>();
        result.addAll(localRepositories);
        result.addAll(Arrays.asList(super.getURLs()));
        return result.toArray(new URL[0]);
    }


    // ------------------------------------------------------ Lifecycle Methods


    
Add a lifecycle event listener to this component.
Params:
listener – The listener to add/**
     * Add a lifecycle event listener to this component.
     *
     * @param listener The listener to add
     */
    @Override
    public void addLifecycleListener(LifecycleListener listener) {
        // NOOP
    }


    
Get the lifecycle listeners associated with this lifecycle. If this
Lifecycle has no listeners registered, a zero-length array is returned.
/**
     * Get the lifecycle listeners associated with this lifecycle. If this
     * Lifecycle has no listeners registered, a zero-length array is returned.
     */
    @Override
    public LifecycleListener[] findLifecycleListeners() {
        return new LifecycleListener[0];
    }


    
Remove a lifecycle event listener from this component.
Params:
listener – The listener to remove/**
     * Remove a lifecycle event listener from this component.
     *
     * @param listener The listener to remove
     */
    @Override
    public void removeLifecycleListener(LifecycleListener listener) {
        // NOOP
    }


    
Obtain the current state of the source component.
Returns:
The current state of the source component./**
     * Obtain the current state of the source component.
     *
     * @return The current state of the source component.
     */
    @Override
    public LifecycleState getState() {
        return state;
    }


    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public String getStateName() {
        return getState().toString();
    }


    @Override
    public void init() {
        state = LifecycleState.INITIALIZED;
    }


    
Start the class loader.
Throws:
LifecycleException – if a lifecycle error occurs/**
     * Start the class loader.
     *
     * @exception LifecycleException if a lifecycle error occurs
     */
    @Override
    public void start() throws LifecycleException {

        state = LifecycleState.STARTING_PREP;

        WebResource[] classesResources = resources.getResources("/WEB-INF/classes");
        for (WebResource classes : classesResources) {
            if (classes.isDirectory() && classes.canRead()) {
                localRepositories.add(classes.getURL());
            }
        }
        WebResource[] jars = resources.listResources("/WEB-INF/lib");
        for (WebResource jar : jars) {
            if (jar.getName().endsWith(".jar") && jar.isFile() && jar.canRead()) {
                localRepositories.add(jar.getURL());
                jarModificationTimes.put(
                        jar.getName(), Long.valueOf(jar.getLastModified()));
            }
        }

        state = LifecycleState.STARTED;
    }


    
Stop the class loader.
Throws:
LifecycleException – if a lifecycle error occurs/**
     * Stop the class loader.
     *
     * @exception LifecycleException if a lifecycle error occurs
     */
    @Override
    public void stop() throws LifecycleException {

        state = LifecycleState.STOPPING_PREP;

        // Clearing references should be done before setting started to
        // false, due to possible side effects
        clearReferences();

        state = LifecycleState.STOPPING;

        resourceEntries.clear();
        jarModificationTimes.clear();
        resources = null;

        permissionList.clear();
        loaderPC.clear();

        state = LifecycleState.STOPPED;
    }


    @Override
    public void destroy() {
        state = LifecycleState.DESTROYING;

        try {
            super.close();
        } catch (IOException ioe) {
            log.warn(sm.getString("webappClassLoader.superCloseFail"), ioe);
        }
        state = LifecycleState.DESTROYED;
    }


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

    protected ClassLoader getJavaseClassLoader() {
        return javaseClassLoader;
    }

    protected void setJavaseClassLoader(ClassLoader classLoader) {
        if (classLoader == null) {
            throw new IllegalArgumentException(
                    sm.getString("webappClassLoader.javaseClassLoaderNull"));
        }
        javaseClassLoader = classLoader;
    }

    
Clear references.
/**
     * Clear references.
     */
    protected void clearReferences() {

        // If the JVM is shutting down, skip the memory leak checks
        if (skipMemoryLeakChecksOnJvmShutdown
            && !resources.getContext().getParent().getState().isAvailable()) {
            // During reloading / redeployment the parent is expected to be
            // available. Parent is not available so this might be a JVM
            // shutdown.
            try {
                Thread dummyHook = new Thread();
                Runtime.getRuntime().addShutdownHook(dummyHook);
                Runtime.getRuntime().removeShutdownHook(dummyHook);
            } catch (IllegalStateException ise) {
                return;
            }
        }

        if (!JreCompat.isGraalAvailable()) {
            // De-register any remaining JDBC drivers
            clearReferencesJdbc();
        }

        // Stop any threads the web application started
        clearReferencesThreads();

        // Clear any references retained in the serialization caches
        if (clearReferencesObjectStreamClassCaches && !JreCompat.isGraalAvailable()) {
            clearReferencesObjectStreamClassCaches();
        }

        // Check for leaks triggered by ThreadLocals loaded by this class loader
        if (clearReferencesThreadLocals && !JreCompat.isGraalAvailable()) {
            checkThreadLocalsForLeaks();
        }

        // Clear RMI Targets loaded by this class loader
        if (clearReferencesRmiTargets) {
            clearReferencesRmiTargets();
        }

         // Clear the IntrospectionUtils cache.
        IntrospectionUtils.clear();

        // Clear the classloader reference in common-logging
        if (clearReferencesLogFactoryRelease) {
            org.apache.juli.logging.LogFactory.release(this);
        }

        // Clear the classloader reference in the VM's bean introspector
        java.beans.Introspector.flushCaches();

        // Clear any custom URLStreamHandlers
        TomcatURLStreamHandlerFactory.release(this);
    }


    
Deregister any JDBC drivers registered by the webapp that the webapp
forgot. This is made unnecessary complex because a) DriverManager
checks the class loader of the calling class (it would be much easier
if it checked the context class loader) b) using reflection would
create a dependency on the DriverManager implementation which can,
and has, changed.
We can't just create an instance of JdbcLeakPrevention as it will be
loaded by the common class loader (since it's .class file is in the
$CATALINA_HOME/lib directory). This would fail DriverManager's check
on the class loader of the calling class. So, we load the bytes via
our parent class loader but define the class with this class loader
so the JdbcLeakPrevention looks like a webapp class to the
DriverManager.
If only apps cleaned up after themselves...
/**
     * Deregister any JDBC drivers registered by the webapp that the webapp
     * forgot. This is made unnecessary complex because a) DriverManager
     * checks the class loader of the calling class (it would be much easier
     * if it checked the context class loader) b) using reflection would
     * create a dependency on the DriverManager implementation which can,
     * and has, changed.
     *
     * We can't just create an instance of JdbcLeakPrevention as it will be
     * loaded by the common class loader (since it's .class file is in the
     * $CATALINA_HOME/lib directory). This would fail DriverManager's check
     * on the class loader of the calling class. So, we load the bytes via
     * our parent class loader but define the class with this class loader
     * so the JdbcLeakPrevention looks like a webapp class to the
     * DriverManager.
     *
     * If only apps cleaned up after themselves...
     */
    private final void clearReferencesJdbc() {
        // We know roughly how big the class will be (~ 1K) so allow 2k as a
        // starting point
        byte[] classBytes = new byte[2048];
        int offset = 0;
        try (InputStream is = getResourceAsStream(
                "org/apache/catalina/loader/JdbcLeakPrevention.class")) {
            int read = is.read(classBytes, offset, classBytes.length-offset);
            while (read > -1) {
                offset += read;
                if (offset == classBytes.length) {
                    // Buffer full - double size
                    byte[] tmp = new byte[classBytes.length * 2];
                    System.arraycopy(classBytes, 0, tmp, 0, classBytes.length);
                    classBytes = tmp;
                }
                read = is.read(classBytes, offset, classBytes.length-offset);
            }
            Class<?> lpClass =
                defineClass("org.apache.catalina.loader.JdbcLeakPrevention",
                    classBytes, 0, offset, this.getClass().getProtectionDomain());
            Object obj = lpClass.getConstructor().newInstance();
            @SuppressWarnings("unchecked")
            List<String> driverNames = (List<String>) obj.getClass().getMethod(
                    "clearJdbcDriverRegistrations").invoke(obj);
            for (String name : driverNames) {
                log.warn(sm.getString("webappClassLoader.clearJdbc",
                        getContextName(), name));
            }
        } catch (Exception e) {
            // So many things to go wrong above...
            Throwable t = ExceptionUtils.unwrapInvocationTargetException(e);
            ExceptionUtils.handleThrowable(t);
            log.warn(sm.getString(
                    "webappClassLoader.jdbcRemoveFailed", getContextName()), t);
        }
    }


    @SuppressWarnings("deprecation") // thread.stop()
    private void clearReferencesThreads() {
        Thread[] threads = getThreads();
        List<Thread> threadsToStop = new ArrayList<>();

        // Iterate over the set of threads
        for (Thread thread : threads) {
            if (thread != null) {
                ClassLoader ccl = thread.getContextClassLoader();
                if (ccl == this) {
                    // Don't warn about this thread
                    if (thread == Thread.currentThread()) {
                        continue;
                    }

                    final String threadName = thread.getName();

                    // JVM controlled threads
                    ThreadGroup tg = thread.getThreadGroup();
                    if (tg != null && JVM_THREAD_GROUP_NAMES.contains(tg.getName())) {
                        // HttpClient keep-alive threads
                        if (clearReferencesHttpClientKeepAliveThread &&
                                threadName.equals("Keep-Alive-Timer")) {
                            thread.setContextClassLoader(parent);
                            log.debug(sm.getString("webappClassLoader.checkThreadsHttpClient"));
                        }

                        // Don't warn about remaining JVM controlled threads
                        continue;
                    }

                    // Skip threads that have already died
                    if (!thread.isAlive()) {
                        continue;
                    }

                    // TimerThread can be stopped safely so treat separately
                    // "java.util.TimerThread" in Sun/Oracle JDK
                    // "java.util.Timer$TimerImpl" in Apache Harmony and in IBM JDK
                    if (thread.getClass().getName().startsWith("java.util.Timer") &&
                            clearReferencesStopTimerThreads) {
                        clearReferencesStopTimerThread(thread);
                        continue;
                    }

                    if (isRequestThread(thread)) {
                        log.warn(sm.getString("webappClassLoader.stackTraceRequestThread",
                                getContextName(), threadName, getStackTrace(thread)));
                    } else {
                        log.warn(sm.getString("webappClassLoader.stackTrace",
                                getContextName(), threadName, getStackTrace(thread)));
                    }

                    // Don't try and stop the threads unless explicitly
                    // configured to do so
                    if (!clearReferencesStopThreads) {
                        continue;
                    }

                    // If the thread has been started via an executor, try
                    // shutting down the executor
                    boolean usingExecutor = false;
                    try {

                        // Runnable wrapped by Thread
                        // "target" in Sun/Oracle JDK
                        // "runnable" in IBM JDK
                        // "action" in Apache Harmony
                        Object target = null;
                        for (String fieldName : new String[] { "target", "runnable", "action" }) {
                            try {
                                Field targetField = thread.getClass().getDeclaredField(fieldName);
                                targetField.setAccessible(true);
                                target = targetField.get(thread);
                                break;
                            } catch (NoSuchFieldException nfe) {
                                continue;
                            }
                        }

                        // "java.util.concurrent" code is in public domain,
                        // so all implementations are similar
                        if (target != null && target.getClass().getCanonicalName() != null &&
                                target.getClass().getCanonicalName().equals(
                                        "java.util.concurrent.ThreadPoolExecutor.Worker")) {
                            Field executorField = target.getClass().getDeclaredField("this$0");
                            executorField.setAccessible(true);
                            Object executor = executorField.get(target);
                            if (executor instanceof ThreadPoolExecutor) {
                                ((ThreadPoolExecutor) executor).shutdownNow();
                                usingExecutor = true;
                            }
                        }
                    } catch (SecurityException | NoSuchFieldException | IllegalArgumentException |
                            IllegalAccessException e) {
                        log.warn(sm.getString("webappClassLoader.stopThreadFail",
                                thread.getName(), getContextName()), e);
                    }

                    // Stopping an executor automatically interrupts the
                    // associated threads. For non-executor threads, interrupt
                    // them here.
                    if (!usingExecutor && !thread.isInterrupted()) {
                        thread.interrupt();
                    }

                    // Threads are expected to take a short time to stop after
                    // being interrupted. Make a note of all threads that are
                    // expected to stop to enable them to be checked at the end
                    // of this method.
                    threadsToStop.add(thread);
                }
            }
        }

        // If thread stopping is enabled, threads should have been stopped above
        // when the executor was shut down or the thread was interrupted but
        // that depends on the thread correctly handling the interrupt. Check
        // each thread and if any are still running give all threads up to a
        // total of 2 seconds to shutdown.
        int count = 0;
        for (Thread t : threadsToStop) {
            while (t.isAlive() && count < 100) {
                try {
                    Thread.sleep(20);
                } catch (InterruptedException e) {
                    // Quit the while loop
                    break;
                }
                count++;
            }
            if (t.isAlive()) {
                // This method is deprecated and for good reason. This is
                // very risky code but is the only option at this point.
                // A *very* good reason for apps to do this clean-up
                // themselves.
                t.stop();
            }
        }
    }


    /*
     * Look at a threads stack trace to see if it is a request thread or not. It
     * isn't perfect, but it should be good-enough for most cases.
     */
    private boolean isRequestThread(Thread thread) {

        StackTraceElement[] elements = thread.getStackTrace();

        if (elements == null || elements.length == 0) {
            // Must have stopped already. Too late to ignore it. Assume not a
            // request processing thread.
            return false;
        }

        // Step through the methods in reverse order looking for calls to any
        // CoyoteAdapter method. All request threads will have this unless
        // Tomcat has been heavily modified - in which case there isn't much we
        // can do.
        for (int i = 0; i < elements.length; i++) {
            StackTraceElement element = elements[elements.length - (i+1)];
            if ("org.apache.catalina.connector.CoyoteAdapter".equals(
                    element.getClassName())) {
                return true;
            }
        }
        return false;
    }


    private void clearReferencesStopTimerThread(Thread thread) {

        // Need to get references to:
        // in Sun/Oracle JDK:
        // - newTasksMayBeScheduled field (in java.util.TimerThread)
        // - queue field
        // - queue.clear()
        // in IBM JDK, Apache Harmony:
        // - cancel() method (in java.util.Timer$TimerImpl)

        try {

            try {
                Field newTasksMayBeScheduledField =
                    thread.getClass().getDeclaredField("newTasksMayBeScheduled");
                newTasksMayBeScheduledField.setAccessible(true);
                Field queueField = thread.getClass().getDeclaredField("queue");
                queueField.setAccessible(true);

                Object queue = queueField.get(thread);

                Method clearMethod = queue.getClass().getDeclaredMethod("clear");
                clearMethod.setAccessible(true);

                synchronized(queue) {
                    newTasksMayBeScheduledField.setBoolean(thread, false);
                    clearMethod.invoke(queue);
                    // In case queue was already empty. Should only be one
                    // thread waiting but use notifyAll() to be safe.
                    queue.notifyAll();
                }

            }catch (NoSuchFieldException nfe){
                Method cancelMethod = thread.getClass().getDeclaredMethod("cancel");
                synchronized(thread) {
                    cancelMethod.setAccessible(true);
                    cancelMethod.invoke(thread);
                }
            }

            log.warn(sm.getString("webappClassLoader.warnTimerThread",
                    getContextName(), thread.getName()));

        } catch (Exception e) {
            // So many things to go wrong above...
            Throwable t = ExceptionUtils.unwrapInvocationTargetException(e);
            ExceptionUtils.handleThrowable(t);
            log.warn(sm.getString(
                    "webappClassLoader.stopTimerThreadFail",
                    thread.getName(), getContextName()), t);
        }
    }

    private void checkThreadLocalsForLeaks() {
        Thread[] threads = getThreads();

        try {
            // Make the fields in the Thread class that store ThreadLocals
            // accessible
            Field threadLocalsField =
                Thread.class.getDeclaredField("threadLocals");
            threadLocalsField.setAccessible(true);
            Field inheritableThreadLocalsField =
                Thread.class.getDeclaredField("inheritableThreadLocals");
            inheritableThreadLocalsField.setAccessible(true);
            // Make the underlying array of ThreadLoad.ThreadLocalMap.Entry objects
            // accessible
            Class<?> tlmClass = Class.forName("java.lang.ThreadLocal$ThreadLocalMap");
            Field tableField = tlmClass.getDeclaredField("table");
            tableField.setAccessible(true);
            Method expungeStaleEntriesMethod = tlmClass.getDeclaredMethod("expungeStaleEntries");
            expungeStaleEntriesMethod.setAccessible(true);

            for (Thread thread : threads) {
                Object threadLocalMap;
                if (thread != null) {

                    // Clear the first map
                    threadLocalMap = threadLocalsField.get(thread);
                    if (null != threadLocalMap) {
                        expungeStaleEntriesMethod.invoke(threadLocalMap);
                        checkThreadLocalMapForLeaks(threadLocalMap, tableField);
                    }

                    // Clear the second map
                    threadLocalMap = inheritableThreadLocalsField.get(thread);
                    if (null != threadLocalMap) {
                        expungeStaleEntriesMethod.invoke(threadLocalMap);
                        checkThreadLocalMapForLeaks(threadLocalMap, tableField);
                    }
                }
            }
        } catch (Throwable t) {
            JreCompat jreCompat = JreCompat.getInstance();
            if (jreCompat.isInstanceOfInaccessibleObjectException(t)) {
                // Must be running on Java 9 without the necessary command line
                // options.
                String currentModule = JreCompat.getInstance().getModuleName(this.getClass());
                log.warn(sm.getString("webappClassLoader.addExportsThreadLocal", currentModule));
            } else {
                ExceptionUtils.handleThrowable(t);
                log.warn(sm.getString(
                        "webappClassLoader.checkThreadLocalsForLeaksFail",
                        getContextName()), t);
            }
        }
    }


    
Analyzes the given thread local map object. Also pass in the field that
points to the internal table to save re-calculating it on every
call to this method.
/**
     * Analyzes the given thread local map object. Also pass in the field that
     * points to the internal table to save re-calculating it on every
     * call to this method.
     */
    private void checkThreadLocalMapForLeaks(Object map,
            Field internalTableField) throws IllegalAccessException,
            NoSuchFieldException {
        if (map != null) {
            Object[] table = (Object[]) internalTableField.get(map);
            if (table != null) {
                for (Object obj : table) {
                    if (obj != null) {
                        boolean keyLoadedByWebapp = false;
                        boolean valueLoadedByWebapp = false;
                        // Check the key
                        Object key = ((Reference<?>) obj).get();
                        if (this.equals(key) || loadedByThisOrChild(key)) {
                            keyLoadedByWebapp = true;
                        }
                        // Check the value
                        Field valueField =
                                obj.getClass().getDeclaredField("value");
                        valueField.setAccessible(true);
                        Object value = valueField.get(obj);
                        if (this.equals(value) || loadedByThisOrChild(value)) {
                            valueLoadedByWebapp = true;
                        }
                        if (keyLoadedByWebapp || valueLoadedByWebapp) {
                            Object[] args = new Object[5];
                            args[0] = getContextName();
                            if (key != null) {
                                args[1] = getPrettyClassName(key.getClass());
                                try {
                                    args[2] = key.toString();
                                } catch (Exception e) {
                                    log.warn(sm.getString(
                                            "webappClassLoader.checkThreadLocalsForLeaks.badKey",
                                            args[1]), e);
                                    args[2] = sm.getString(
                                            "webappClassLoader.checkThreadLocalsForLeaks.unknown");
                                }
                            }
                            if (value != null) {
                                args[3] = getPrettyClassName(value.getClass());
                                try {
                                    args[4] = value.toString();
                                } catch (Exception e) {
                                    log.warn(sm.getString(
                                            "webappClassLoader.checkThreadLocalsForLeaks.badValue",
                                            args[3]), e);
                                    args[4] = sm.getString(
                                            "webappClassLoader.checkThreadLocalsForLeaks.unknown");
                                }
                            }
                            if (valueLoadedByWebapp) {
                                log.error(sm.getString(
                                        "webappClassLoader.checkThreadLocalsForLeaks",
                                        args));
                            } else if (value == null) {
                                if (log.isDebugEnabled()) {
                                    log.debug(sm.getString(
                                            "webappClassLoader.checkThreadLocalsForLeaksNull",
                                            args));
                                }
                            } else {
                                if (log.isDebugEnabled()) {
                                    log.debug(sm.getString(
                                            "webappClassLoader.checkThreadLocalsForLeaksNone",
                                            args));
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    private String getPrettyClassName(Class<?> clazz) {
        String name = clazz.getCanonicalName();
        if (name==null){
            name = clazz.getName();
        }
        return name;
    }

    private String getStackTrace(Thread thread) {
        StringBuilder builder = new StringBuilder();
        for (StackTraceElement ste : thread.getStackTrace()) {
            builder.append("\n ").append(ste);
        }
        return builder.toString();
    }

    
Params:
o – object to test, may be null
Returns:
true if o has been loaded by the current classloader
or one of its descendants./**
     * @param o object to test, may be null
     * @return <code>true</code> if o has been loaded by the current classloader
     * or one of its descendants.
     */
    private boolean loadedByThisOrChild(Object o) {
        if (o == null) {
            return false;
        }

        Class<?> clazz;
        if (o instanceof Class) {
            clazz = (Class<?>) o;
        } else {
            clazz = o.getClass();
        }

        ClassLoader cl = clazz.getClassLoader();
        while (cl != null) {
            if (cl == this) {
                return true;
            }
            cl = cl.getParent();
        }

        if (o instanceof Collection<?>) {
            Iterator<?> iter = ((Collection<?>) o).iterator();
            try {
                while (iter.hasNext()) {
                    Object entry = iter.next();
                    if (loadedByThisOrChild(entry)) {
                        return true;
                    }
                }
            } catch (ConcurrentModificationException e) {
                log.warn(sm.getString(
                        "webappClassLoader.loadedByThisOrChildFail", clazz.getName(), getContextName()),
                        e);
            }
        }
        return false;
    }

    /*
     * Get the set of current threads as an array.
     */
    private Thread[] getThreads() {
        // Get the current thread group
        ThreadGroup tg = Thread.currentThread().getThreadGroup();
        // Find the root thread group
        try {
            while (tg.getParent() != null) {
                tg = tg.getParent();
            }
        } catch (SecurityException se) {
            String msg = sm.getString(
                    "webappClassLoader.getThreadGroupError", tg.getName());
            if (log.isDebugEnabled()) {
                log.debug(msg, se);
            } else {
                log.warn(msg);
            }
        }

        int threadCountGuess = tg.activeCount() + 50;
        Thread[] threads = new Thread[threadCountGuess];
        int threadCountActual = tg.enumerate(threads);
        // Make sure we don't miss any threads
        while (threadCountActual == threadCountGuess) {
            threadCountGuess *=2;
            threads = new Thread[threadCountGuess];
            // Note tg.enumerate(Thread[]) silently ignores any threads that
            // can't fit into the array
            threadCountActual = tg.enumerate(threads);
        }

        return threads;
    }


    
This depends on the internals of the Sun JVM so it does everything by
reflection.
/**
     * This depends on the internals of the Sun JVM so it does everything by
     * reflection.
     */
    private void clearReferencesRmiTargets() {
        try {
            // Need access to the ccl field of sun.rmi.transport.Target to find
            // the leaks
            Class<?> objectTargetClass =
                Class.forName("sun.rmi.transport.Target");
            Field cclField = objectTargetClass.getDeclaredField("ccl");
            cclField.setAccessible(true);
            // Need access to the stub field to report the leaks
            Field stubField = objectTargetClass.getDeclaredField("stub");
            stubField.setAccessible(true);

            // Clear the objTable map
            Class<?> objectTableClass = Class.forName("sun.rmi.transport.ObjectTable");
            Field objTableField = objectTableClass.getDeclaredField("objTable");
            objTableField.setAccessible(true);
            Object objTable = objTableField.get(null);
            if (objTable == null) {
                return;
            }
            Field tableLockField = objectTableClass.getDeclaredField("tableLock");
            tableLockField.setAccessible(true);
            Object tableLock = tableLockField.get(null);

            synchronized (tableLock) {
                // Iterate over the values in the table
                if (objTable instanceof Map<?,?>) {
                    Iterator<?> iter = ((Map<?,?>) objTable).values().iterator();
                    while (iter.hasNext()) {
                        Object obj = iter.next();
                        Object cclObject = cclField.get(obj);
                        if (this == cclObject) {
                            iter.remove();
                            Object stubObject = stubField.get(obj);
                            log.error(sm.getString("webappClassLoader.clearRmi",
                                    stubObject.getClass().getName(), stubObject));
                        }
                    }
                }

                // Clear the implTable map
                Field implTableField = objectTableClass.getDeclaredField("implTable");
                implTableField.setAccessible(true);
                Object implTable = implTableField.get(null);
                if (implTable == null) {
                    return;
                }

                // Iterate over the values in the table
                if (implTable instanceof Map<?,?>) {
                    Iterator<?> iter = ((Map<?,?>) implTable).values().iterator();
                    while (iter.hasNext()) {
                        Object obj = iter.next();
                        Object cclObject = cclField.get(obj);
                        if (this == cclObject) {
                            iter.remove();
                        }
                    }
                }
            }
        } catch (ClassNotFoundException e) {
            log.info(sm.getString("webappClassLoader.clearRmiInfo",
                    getContextName()), e);
        } catch (SecurityException | NoSuchFieldException | IllegalArgumentException |
                IllegalAccessException e) {
            log.warn(sm.getString("webappClassLoader.clearRmiFail",
                    getContextName()), e);
        } catch (Exception e) {
            JreCompat jreCompat = JreCompat.getInstance();
            if (jreCompat.isInstanceOfInaccessibleObjectException(e)) {
                // Must be running on Java 9 without the necessary command line
                // options.
                String currentModule = JreCompat.getInstance().getModuleName(this.getClass());
                log.warn(sm.getString("webappClassLoader.addExportsRmi", currentModule));
            } else {
                // Re-throw all other exceptions
                throw e;
            }
        }
    }


    private void clearReferencesObjectStreamClassCaches() {
        try {
            Class<?> clazz = Class.forName("java.io.ObjectStreamClass$Caches");
            clearCache(clazz, "localDescs");
            clearCache(clazz, "reflectors");
        } catch (ReflectiveOperationException | SecurityException | ClassCastException e) {
            log.warn(sm.getString(
                    "webappClassLoader.clearObjectStreamClassCachesFail", getContextName()), e);
        } catch (Exception e) {
            JreCompat jreCompat = JreCompat.getInstance();
            if (jreCompat.isInstanceOfInaccessibleObjectException(e)) {
                // Must be running on Java 9 without the necessary command line
                // options.
                String currentModule = JreCompat.getInstance().getModuleName(this.getClass());
                log.warn(sm.getString("webappClassLoader.addExportsJavaIo", currentModule));
                return;
            } else {
                // Re-throw all other exceptions
                throw e;
            }
        }
    }


    private void clearCache(Class<?> target, String mapName)
            throws ReflectiveOperationException, SecurityException, ClassCastException {
        Field f = target.getDeclaredField(mapName);
        f.setAccessible(true);
        Map<?,?> map = (Map<?,?>) f.get(null);
        Iterator<?> keys = map.keySet().iterator();
        while (keys.hasNext()) {
            Object key = keys.next();
            if (key instanceof Reference) {
                Object clazz = ((Reference<?>) key).get();
                if (loadedByThisOrChild(clazz)) {
                    keys.remove();
                }
            }
        }
    }


    
Find specified class in local repositories.
Params:
name – The binary name of the class to be loaded
Returns:
the loaded class, or null if the class isn't found/**
     * Find specified class in local repositories.
     *
     * @param name The binary name of the class to be loaded
     *
     * @return the loaded class, or null if the class isn't found
     */
    protected Class<?> findClassInternal(String name) {

        checkStateForResourceLoading(name);

        if (name == null) {
            return null;
        }
        String path = binaryNameToPath(name, true);

        ResourceEntry entry = resourceEntries.get(path);
        WebResource resource = null;

        if (entry == null) {
            resource = resources.getClassLoaderResource(path);

            if (!resource.exists()) {
                return null;
            }

            entry = new ResourceEntry();
            entry.lastModified = resource.getLastModified();

            // Add the entry in the local resource repository
            synchronized (resourceEntries) {
                // Ensures that all the threads which may be in a race to load
                // a particular class all end up with the same ResourceEntry
                // instance
                ResourceEntry entry2 = resourceEntries.get(path);
                if (entry2 == null) {
                    resourceEntries.put(path, entry);
                } else {
                    entry = entry2;
                }
            }
        }

        Class<?> clazz = entry.loadedClass;
        if (clazz != null)
            return clazz;

        synchronized (JreCompat.isGraalAvailable() ? this : getClassLoadingLock(name)) {
            clazz = entry.loadedClass;
            if (clazz != null)
                return clazz;

            if (resource == null) {
                resource = resources.getClassLoaderResource(path);
            }

            if (!resource.exists()) {
                return null;
            }

            byte[] binaryContent = resource.getContent();
            if (binaryContent == null) {
                // Something went wrong reading the class bytes (and will have
                // been logged at debug level).
                return null;
            }
            Manifest manifest = resource.getManifest();
            URL codeBase = resource.getCodeBase();
            Certificate[] certificates = resource.getCertificates();

            if (transformers.size() > 0) {
                // If the resource is a class just being loaded, decorate it
                // with any attached transformers

                // Ignore leading '/' and trailing CLASS_FILE_SUFFIX
                // Should be cheaper than replacing '.' by '/' in class name.
                String internalName = path.substring(1, path.length() - CLASS_FILE_SUFFIX.length());

                for (ClassFileTransformer transformer : this.transformers) {
                    try {
                        byte[] transformed = transformer.transform(
                                this, internalName, null, null, binaryContent);
                        if (transformed != null) {
                            binaryContent = transformed;
                        }
                    } catch (IllegalClassFormatException e) {
                        log.error(sm.getString("webappClassLoader.transformError", name), e);
                        return null;
                    }
                }
            }

            // Looking up the package
            String packageName = null;
            int pos = name.lastIndexOf('.');
            if (pos != -1)
                packageName = name.substring(0, pos);

            Package pkg = null;

            if (packageName != null) {
                pkg = getPackage(packageName);
                // Define the package (if null)
                if (pkg == null) {
                    try {
                        if (manifest == null) {
                            definePackage(packageName, null, null, null, null, null, null, null);
                        } else {
                            definePackage(packageName, manifest, codeBase);
                        }
                    } catch (IllegalArgumentException e) {
                        // Ignore: normal error due to dual definition of package
                    }
                    pkg = getPackage(packageName);
                }
            }

            if (securityManager != null) {

                // Checking sealing
                if (pkg != null) {
                    boolean sealCheck = true;
                    if (pkg.isSealed()) {
                        sealCheck = pkg.isSealed(codeBase);
                    } else {
                        sealCheck = (manifest == null) || !isPackageSealed(packageName, manifest);
                    }
                    if (!sealCheck)
                        throw new SecurityException
                            ("Sealing violation loading " + name + " : Package "
                             + packageName + " is sealed.");
                }

            }

            try {
                clazz = defineClass(name, binaryContent, 0,
                        binaryContent.length, new CodeSource(codeBase, certificates));
            } catch (UnsupportedClassVersionError ucve) {
                throw new UnsupportedClassVersionError(
                        ucve.getLocalizedMessage() + " " +
                        sm.getString("webappClassLoader.wrongVersion",
                                name));
            }
            entry.loadedClass = clazz;
        }

        return clazz;
    }


    private String binaryNameToPath(String binaryName, boolean withLeadingSlash) {
        // 1 for leading '/', 6 for ".class"
        StringBuilder path = new StringBuilder(7 + binaryName.length());
        if (withLeadingSlash) {
            path.append('/');
        }
        path.append(binaryName.replace('.', '/'));
        path.append(CLASS_FILE_SUFFIX);
        return path.toString();
    }


    private String nameToPath(String name) {
        if (name.startsWith("/")) {
            return name;
        }
        StringBuilder path = new StringBuilder(
                1 + name.length());
        path.append('/');
        path.append(name);
        return path.toString();
    }


    
Returns true if the specified package name is sealed according to the
given manifest.
Params:
name – Path name to check
man – Associated manifest
Returns:
true if the manifest associated says it is sealed/**
     * Returns true if the specified package name is sealed according to the
     * given manifest.
     *
     * @param name Path name to check
     * @param man Associated manifest
     * @return <code>true</code> if the manifest associated says it is sealed
     */
    protected boolean isPackageSealed(String name, Manifest man) {

        String path = name.replace('.', '/') + '/';
        Attributes attr = man.getAttributes(path);
        String sealed = null;
        if (attr != null) {
            sealed = attr.getValue(Name.SEALED);
        }
        if (sealed == null) {
            if ((attr = man.getMainAttributes()) != null) {
                sealed = attr.getValue(Name.SEALED);
            }
        }
        return "true".equalsIgnoreCase(sealed);

    }


    
Finds the class with the given name if it has previously been
loaded and cached by this class loader, and return the Class object.
If this class has not been cached, return null.
Params:
name – The binary name of the resource to return
Returns:
a loaded class/**
     * Finds the class with the given name if it has previously been
     * loaded and cached by this class loader, and return the Class object.
     * If this class has not been cached, return <code>null</code>.
     *
     * @param name The binary name of the resource to return
     * @return a loaded class
     */
    protected Class<?> findLoadedClass0(String name) {

        String path = binaryNameToPath(name, true);

        ResourceEntry entry = resourceEntries.get(path);
        if (entry != null) {
            return entry.loadedClass;
        }
        return null;
    }


    
Refresh the system policy file, to pick up eventual changes.
/**
     * Refresh the system policy file, to pick up eventual changes.
     */
    protected void refreshPolicy() {

        try {
            // The policy file may have been modified to adjust
            // permissions, so we're reloading it when loading or
            // reloading a Context
            Policy policy = Policy.getPolicy();
            policy.refresh();
        } catch (AccessControlException e) {
            // Some policy files may restrict this, even for the core,
            // so this exception is ignored
        }

    }


    
Filter classes.
Params:
name – class name
isClassName – true if name is a class name,
               false if name is a resource name
Returns:
true if the class should be filtered/**
     * Filter classes.
     *
     * @param name class name
     * @param isClassName <code>true</code> if name is a class name,
     *                <code>false</code> if name is a resource name
     * @return <code>true</code> if the class should be filtered
     */
    protected boolean filter(String name, boolean isClassName) {

        if (name == null)
            return false;

        char ch;
        if (name.startsWith("jakarta")) {
            /* 7 == length("jakarta") */
            if (name.length() == 7) {
                return false;
            }
            ch = name.charAt(7);
            if (isClassName && ch == '.') {
                /* 8 == length("jakarta.") */
                if (name.startsWith("servlet.jsp.jstl.", 8)) {
                    return false;
                }
                if (name.startsWith("el.", 8) ||
                    name.startsWith("servlet.", 8) ||
                    name.startsWith("websocket.", 8) ||
                    name.startsWith("security.auth.message.", 8)) {
                    return true;
                }
            } else if (!isClassName && ch == '/') {
                /* 8 == length("jakarta/") */
                if (name.startsWith("servlet/jsp/jstl/", 8)) {
                    return false;
                }
                if (name.startsWith("el/", 8) ||
                    name.startsWith("servlet/", 8) ||
                    name.startsWith("websocket/", 8) ||
                    name.startsWith("security/auth/message/", 8)) {
                    return true;
                }
            }
        } else if (name.startsWith("javax")) {
            /* 5 == length("javax") */
            if (name.length() == 5) {
                return false;
            }
            ch = name.charAt(5);
            if (isClassName && ch == '.') {
                /* 6 == length("javax.") */
                if (name.startsWith("websocket.", 6)) {
                    return true;
                }
            } else if (!isClassName && ch == '/') {
                /* 6 == length("javax/") */
                if (name.startsWith("websocket/", 6)) {
                    return true;
                }
            }
        } else if (name.startsWith("org")) {
            /* 3 == length("org") */
            if (name.length() == 3) {
                return false;
            }
            ch = name.charAt(3);
            if (isClassName && ch == '.') {
                /* 4 == length("org.") */
                if (name.startsWith("apache.", 4)) {
                    /* 11 == length("org.apache.") */
                    if (name.startsWith("tomcat.jdbc.", 11)) {
                        return false;
                    }
                    if (name.startsWith("el.", 11) ||
                        name.startsWith("catalina.", 11) ||
                        name.startsWith("jasper.", 11) ||
                        name.startsWith("juli.", 11) ||
                        name.startsWith("tomcat.", 11) ||
                        name.startsWith("naming.", 11) ||
                        name.startsWith("coyote.", 11)) {
                        return true;
                    }
                }
            } else if (!isClassName && ch == '/') {
                /* 4 == length("org/") */
                if (name.startsWith("apache/", 4)) {
                    /* 11 == length("org/apache/") */
                    if (name.startsWith("tomcat/jdbc/", 11)) {
                        return false;
                    }
                    if (name.startsWith("el/", 11) ||
                        name.startsWith("catalina/", 11) ||
                        name.startsWith("jasper/", 11) ||
                        name.startsWith("juli/", 11) ||
                        name.startsWith("tomcat/", 11) ||
                        name.startsWith("naming/", 11) ||
                        name.startsWith("coyote/", 11)) {
                        return true;
                    }
                }
            }
        }
        return false;
    }


    @Override
    protected void addURL(URL url) {
        super.addURL(url);
        hasExternalRepositories = true;
    }


    @Override
    public String getWebappName() {
        return getContextName();
    }


    @Override
    public String getHostName() {
        if (resources != null) {
            Container host = resources.getContext().getParent();
            if (host != null) {
                return host.getName();
            }
        }
        return null;
    }


    @Override
    public String getServiceName() {
        if (resources != null) {
            Container host = resources.getContext().getParent();
            if (host != null) {
                Container engine = host.getParent();
                if (engine != null) {
                    return engine.getName();
                }
            }
        }
        return null;
    }


    @Override
    public boolean hasLoggingConfig() {
        if (Globals.IS_SECURITY_ENABLED) {
            Boolean result = AccessController.doPrivileged(new PrivilegedHasLoggingConfig());
            return result.booleanValue();
        } else {
            return findResource("logging.properties") != null;
        }
    }


    private class PrivilegedHasLoggingConfig implements PrivilegedAction<Boolean> {

        @Override
        public Boolean run() {
            return Boolean.valueOf(findResource("logging.properties") != null);
        }
    }


    private static class CombinedEnumeration implements Enumeration<URL> {

        private final Enumeration<URL>[] sources;
        private int index = 0;

        public CombinedEnumeration(Enumeration<URL> enum1, Enumeration<URL> enum2) {
            @SuppressWarnings("unchecked")
            Enumeration<URL>[] sources = new Enumeration[] { enum1, enum2 };
            this.sources = sources;
        }


        @Override
        public boolean hasMoreElements() {
            return inc();
        }


        @Override
        public URL nextElement() {
            if (inc()) {
                return sources[index].nextElement();
            }
            throw new NoSuchElementException();
        }


        private boolean inc() {
            while (index < sources.length) {
                if (sources[index].hasMoreElements()) {
                    return true;
                }
                index++;
            }
            return false;
        }
    }
}