java/8 : sun/misc/URLClassPath.java

URLClassPath
https://openjdk.java.net/
GPLv2 + Classpath Exception
/*
 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.misc;

import java.util.*;
import java.util.jar.JarFile;
import sun.misc.JarIndex;
import sun.misc.InvalidJarIndexException;
import sun.net.www.ParseUtil;
import java.util.zip.ZipEntry;
import java.util.jar.JarEntry;
import java.util.jar.Manifest;
import java.util.jar.Attributes;
import java.util.jar.Attributes.Name;
import java.net.JarURLConnection;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLConnection;
import java.net.HttpURLConnection;
import java.net.URLStreamHandler;
import java.net.URLStreamHandlerFactory;
import java.io.*;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.AccessControlException;
import java.security.CodeSigner;
import java.security.Permission;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;
import java.security.cert.Certificate;
import sun.misc.FileURLMapper;
import sun.net.util.URLUtil;
import sun.security.action.GetPropertyAction;

This class is used to maintain a search path of URLs for loading classes
and resources from both JAR files and directories.
Author:  David Connelly/**
 * This class is used to maintain a search path of URLs for loading classes
 * and resources from both JAR files and directories.
 *
 * @author  David Connelly
 */
public class URLClassPath {
    final static String USER_AGENT_JAVA_VERSION = "UA-Java-Version";
    final static String JAVA_VERSION;
    private static final boolean DEBUG;
    private static final boolean DEBUG_LOOKUP_CACHE;
    private static final boolean DISABLE_JAR_CHECKING;
    private static final boolean DISABLE_ACC_CHECKING;
    private static final boolean DISABLE_CP_URL_CHECK;
    private static final boolean DEBUG_CP_URL_CHECK;

    static {
        JAVA_VERSION = java.security.AccessController.doPrivileged(
            new GetPropertyAction("java.version"));
        DEBUG        = (java.security.AccessController.doPrivileged(
            new GetPropertyAction("sun.misc.URLClassPath.debug")) != null);
        DEBUG_LOOKUP_CACHE = (java.security.AccessController.doPrivileged(
            new GetPropertyAction("sun.misc.URLClassPath.debugLookupCache")) != null);
        String p = java.security.AccessController.doPrivileged(
            new GetPropertyAction("sun.misc.URLClassPath.disableJarChecking"));
        DISABLE_JAR_CHECKING = p != null ? p.equals("true") || p.equals("") : false;

        p = AccessController.doPrivileged(
            new GetPropertyAction("jdk.net.URLClassPath.disableRestrictedPermissions"));
        DISABLE_ACC_CHECKING = p != null ? p.equals("true") || p.equals("") : false;

        // This property will be removed in a later release
        p = AccessController.doPrivileged(
            new GetPropertyAction("jdk.net.URLClassPath.disableClassPathURLCheck", "true"));

        DISABLE_CP_URL_CHECK = p != null ? p.equals("true") || p.isEmpty() : false;
        DEBUG_CP_URL_CHECK = "debug".equals(p);
    }

    /* The original search path of URLs. */
    private ArrayList<URL> path = new ArrayList<URL>();

    /* The stack of unopened URLs */
    Stack<URL> urls = new Stack<URL>();

    /* The resulting search path of Loaders */
    ArrayList<Loader> loaders = new ArrayList<Loader>();

    /* Map of each URL opened to its corresponding Loader */
    HashMap<String, Loader> lmap = new HashMap<String, Loader>();

    /* The jar protocol handler to use when creating new URLs */
    private URLStreamHandler jarHandler;

    /* Whether this URLClassLoader has been closed yet */
    private boolean closed = false;

    /* The context to be used when loading classes and resources.  If non-null
     * this is the context that was captured during the creation of the
     * URLClassLoader. null implies no additional security restrictions. */
    private final AccessControlContext acc;

    Creates a new URLClassPath for the given URLs. The URLs will be
searched in the order specified for classes and resources. A URL
ending with a '/' is assumed to refer to a directory. Otherwise,
the URL is assumed to refer to a JAR file.
Params: urls – the directory and JAR file URLs to search for classes
       and resources
factory – the URLStreamHandlerFactory to use when creating new URLs
acc – the context to be used when loading classes and resources, may
           be null/**
     * Creates a new URLClassPath for the given URLs. The URLs will be
     * searched in the order specified for classes and resources. A URL
     * ending with a '/' is assumed to refer to a directory. Otherwise,
     * the URL is assumed to refer to a JAR file.
     *
     * @param urls the directory and JAR file URLs to search for classes
     *        and resources
     * @param factory the URLStreamHandlerFactory to use when creating new URLs
     * @param acc the context to be used when loading classes and resources, may
     *            be null
     */
    public URLClassPath(URL[] urls,
                        URLStreamHandlerFactory factory,
                        AccessControlContext acc) {
        for (int i = 0; i < urls.length; i++) {
            path.add(urls[i]);
        }
        push(urls);
        if (factory != null) {
            jarHandler = factory.createURLStreamHandler("jar");
        }
        if (DISABLE_ACC_CHECKING)
            this.acc = null;
        else
            this.acc = acc;
    }

    Constructs a URLClassPath with no additional security restrictions.
Used by code that implements the class path.
/**
     * Constructs a URLClassPath with no additional security restrictions.
     * Used by code that implements the class path.
     */
    public URLClassPath(URL[] urls) {
        this(urls, null, null);
    }

    public URLClassPath(URL[] urls, AccessControlContext acc) {
        this(urls, null, acc);
    }

    public synchronized List<IOException> closeLoaders() {
        if (closed) {
            return Collections.emptyList();
        }
        List<IOException> result = new LinkedList<IOException>();
        for (Loader loader : loaders) {
            try {
                loader.close();
            } catch (IOException e) {
                result.add (e);
            }
        }
        closed = true;
        return result;
    }

    Appends the specified URL to the search path of directory and JAR
file URLs from which to load classes and resources.

If the URL specified is null or is already in the list of
URLs, then invoking this method has no effect.
/**
     * Appends the specified URL to the search path of directory and JAR
     * file URLs from which to load classes and resources.
     * <p>
     * If the URL specified is null or is already in the list of
     * URLs, then invoking this method has no effect.
     */
    public synchronized void addURL(URL url) {
        if (closed)
            return;
        synchronized (urls) {
            if (url == null || path.contains(url))
                return;

            urls.add(0, url);
            path.add(url);

            if (lookupCacheURLs != null) {
                // The lookup cache is no longer valid, since getLookupCache()
                // does not consider the newly added url.
                disableAllLookupCaches();
            }
        }
    }

    Returns the original search path of URLs.
/**
     * Returns the original search path of URLs.
     */
    public URL[] getURLs() {
        synchronized (urls) {
            return path.toArray(new URL[path.size()]);
        }
    }

    Finds the resource with the specified name on the URL search path
or null if not found or security check fails.
Params: name –      the name of the resource
check –     whether to perform a security check
Returns: a URL for the resource, or null
if the resource could not be found./**
     * Finds the resource with the specified name on the URL search path
     * or null if not found or security check fails.
     *
     * @param name      the name of the resource
     * @param check     whether to perform a security check
     * @return a <code>URL</code> for the resource, or <code>null</code>
     * if the resource could not be found.
     */
    public URL findResource(String name, boolean check) {
        Loader loader;
        int[] cache = getLookupCache(name);
        for (int i = 0; (loader = getNextLoader(cache, i)) != null; i++) {
            URL url = loader.findResource(name, check);
            if (url != null) {
                return url;
            }
        }
        return null;
    }

    Finds the first Resource on the URL search path which has the specified
name. Returns null if no Resource could be found.
Params: name – the name of the Resource
check –     whether to perform a security check
Returns: the Resource, or null if not found/**
     * Finds the first Resource on the URL search path which has the specified
     * name. Returns null if no Resource could be found.
     *
     * @param name the name of the Resource
     * @param check     whether to perform a security check
     * @return the Resource, or null if not found
     */
    public Resource getResource(String name, boolean check) {
        if (DEBUG) {
            System.err.println("URLClassPath.getResource(\"" + name + "\")");
        }

        Loader loader;
        int[] cache = getLookupCache(name);
        for (int i = 0; (loader = getNextLoader(cache, i)) != null; i++) {
            Resource res = loader.getResource(name, check);
            if (res != null) {
                return res;
            }
        }
        return null;
    }

    Finds all resources on the URL search path with the given name.
Returns an enumeration of the URL objects.
Params: name – the resource name
Returns: an Enumeration of all the urls having the specified name/**
     * Finds all resources on the URL search path with the given name.
     * Returns an enumeration of the URL objects.
     *
     * @param name the resource name
     * @return an Enumeration of all the urls having the specified name
     */
    public Enumeration<URL> findResources(final String name,
                                     final boolean check) {
        return new Enumeration<URL>() {
            private int index = 0;
            private int[] cache = getLookupCache(name);
            private URL url = null;

            private boolean next() {
                if (url != null) {
                    return true;
                } else {
                    Loader loader;
                    while ((loader = getNextLoader(cache, index++)) != null) {
                        url = loader.findResource(name, check);
                        if (url != null) {
                            return true;
                        }
                    }
                    return false;
                }
            }

            public boolean hasMoreElements() {
                return next();
            }

            public URL nextElement() {
                if (!next()) {
                    throw new NoSuchElementException();
                }
                URL u = url;
                url = null;
                return u;
            }
        };
    }

    public Resource getResource(String name) {
        return getResource(name, true);
    }

    Finds all resources on the URL search path with the given name.
Returns an enumeration of the Resource objects.
Params: name – the resource name
Returns: an Enumeration of all the resources having the specified name/**
     * Finds all resources on the URL search path with the given name.
     * Returns an enumeration of the Resource objects.
     *
     * @param name the resource name
     * @return an Enumeration of all the resources having the specified name
     */
    public Enumeration<Resource> getResources(final String name,
                                    final boolean check) {
        return new Enumeration<Resource>() {
            private int index = 0;
            private int[] cache = getLookupCache(name);
            private Resource res = null;

            private boolean next() {
                if (res != null) {
                    return true;
                } else {
                    Loader loader;
                    while ((loader = getNextLoader(cache, index++)) != null) {
                        res = loader.getResource(name, check);
                        if (res != null) {
                            return true;
                        }
                    }
                    return false;
                }
            }

            public boolean hasMoreElements() {
                return next();
            }

            public Resource nextElement() {
                if (!next()) {
                    throw new NoSuchElementException();
                }
                Resource r = res;
                res = null;
                return r;
            }
        };
    }

    public Enumeration<Resource> getResources(final String name) {
        return getResources(name, true);
    }

    private static volatile boolean lookupCacheEnabled
        = "true".equals(VM.getSavedProperty("sun.cds.enableSharedLookupCache"));
    private URL[] lookupCacheURLs;
    private ClassLoader lookupCacheLoader;

    synchronized void initLookupCache(ClassLoader loader) {
        if ((lookupCacheURLs = getLookupCacheURLs(loader)) != null) {
            lookupCacheLoader = loader;
        } else {
            // This JVM instance does not support lookup cache.
            disableAllLookupCaches();
        }
    }

    static void disableAllLookupCaches() {
        lookupCacheEnabled = false;
    }

    private static native URL[] getLookupCacheURLs(ClassLoader loader);
    private static native int[] getLookupCacheForClassLoader(ClassLoader loader,
                                                             String name);
    private static native boolean knownToNotExist0(ClassLoader loader,
                                                   String className);

    synchronized boolean knownToNotExist(String className) {
        if (lookupCacheURLs != null && lookupCacheEnabled) {
            return knownToNotExist0(lookupCacheLoader, className);
        }

        // Don't know if this class exists or not -- need to do a full search.
        return false;
    }

    Returns an array of the index to lookupCacheURLs that may
contain the specified resource. The values in the returned
array are in strictly ascending order and must be a valid index
to lookupCacheURLs array.
This method returns an empty array if the specified resource
cannot be found in this URLClassPath. If there is no lookup
cache or it's disabled, this method returns null and the lookup
should search the entire classpath.
Example: if lookupCacheURLs contains {a.jar, b.jar, c.jar, d.jar}
and package "foo" only exists in a.jar and c.jar,
getLookupCache("foo/Bar.class") will return {0, 2}
Params: name – the resource name
Returns: an array of the index to lookupCacheURLs that may contain the
        specified resource; or null if no lookup cache is used./**
     * Returns an array of the index to lookupCacheURLs that may
     * contain the specified resource. The values in the returned
     * array are in strictly ascending order and must be a valid index
     * to lookupCacheURLs array.
     *
     * This method returns an empty array if the specified resource
     * cannot be found in this URLClassPath. If there is no lookup
     * cache or it's disabled, this method returns null and the lookup
     * should search the entire classpath.
     *
     * Example: if lookupCacheURLs contains {a.jar, b.jar, c.jar, d.jar}
     * and package "foo" only exists in a.jar and c.jar,
     * getLookupCache("foo/Bar.class") will return {0, 2}
     *
     * @param name the resource name
     * @return an array of the index to lookupCacheURLs that may contain the
     *         specified resource; or null if no lookup cache is used.
     */
    private synchronized int[] getLookupCache(String name) {
        if (lookupCacheURLs == null || !lookupCacheEnabled) {
            return null;
        }

        int[] cache = getLookupCacheForClassLoader(lookupCacheLoader, name);
        if (cache != null && cache.length > 0) {
            int maxindex = cache[cache.length - 1]; // cache[] is strictly ascending.
            if (!ensureLoaderOpened(maxindex)) {
                if (DEBUG_LOOKUP_CACHE) {
                    System.out.println("Expanded loaders FAILED " +
                                       loaders.size() + " for maxindex=" + maxindex);
                }
                return null;
            }
        }

        return cache;
    }

    private boolean ensureLoaderOpened(int index) {
        if (loaders.size() <= index) {
            // Open all Loaders up to, and including, index
            if (getLoader(index) == null) {
                return false;
            }
            if (!lookupCacheEnabled) {
                // cache was invalidated as the result of the above call.
                return false;
            }
            if (DEBUG_LOOKUP_CACHE) {
                System.out.println("Expanded loaders " + loaders.size() +
                                   " to index=" + index);
            }
        }
        return true;
    }

    /*
     * The CLASS-PATH attribute was expanded by the VM when building
     * the resource lookup cache in the same order as the getLoader
     * method does. This method validates if the URL from the lookup
     * cache matches the URL of the Loader at the given index;
     * otherwise, this method disables the lookup cache.
     */
    private synchronized void validateLookupCache(int index,
                                                  String urlNoFragString) {
        if (lookupCacheURLs != null && lookupCacheEnabled) {
            if (index < lookupCacheURLs.length &&
                urlNoFragString.equals(
                    URLUtil.urlNoFragString(lookupCacheURLs[index]))) {
                return;
            }
            if (DEBUG || DEBUG_LOOKUP_CACHE) {
                System.out.println("WARNING: resource lookup cache invalidated "
                                   + "for lookupCacheLoader at " + index);
            }
            disableAllLookupCaches();
        }
    }

    Returns the next Loader that may contain the resource to
lookup. If the given cache is null, return loaders.get(index)
that may be lazily created; otherwise, cache[index] is the next
Loader that may contain the resource to lookup and so returns
loaders.get(cache[index]).
If cache is non-null, loaders.get(cache[index]) must be present.
Params: cache – lookup cache. If null, search the entire class path
index – index to the given cache array; or to the loaders list./**
     * Returns the next Loader that may contain the resource to
     * lookup. If the given cache is null, return loaders.get(index)
     * that may be lazily created; otherwise, cache[index] is the next
     * Loader that may contain the resource to lookup and so returns
     * loaders.get(cache[index]).
     *
     * If cache is non-null, loaders.get(cache[index]) must be present.
     *
     * @param cache lookup cache. If null, search the entire class path
     * @param index index to the given cache array; or to the loaders list.
     */
    private synchronized Loader getNextLoader(int[] cache, int index) {
        if (closed) {
            return null;
        }
        if (cache != null) {
            if (index < cache.length) {
                Loader loader = loaders.get(cache[index]);
                if (DEBUG_LOOKUP_CACHE) {
                    System.out.println("HASCACHE: Loading from : " + cache[index]
                                       + " = " + loader.getBaseURL());
                }
                return loader;
            } else {
                return null; // finished iterating over cache[]
            }
        } else {
            return getLoader(index);
        }
    }

    /*
     * Returns the Loader at the specified position in the URL search
     * path. The URLs are opened and expanded as needed. Returns null
     * if the specified index is out of range.
     */
     private synchronized Loader getLoader(int index) {
        if (closed) {
            return null;
        }
         // Expand URL search path until the request can be satisfied
         // or the URL stack is empty.
        while (loaders.size() < index + 1) {
            // Pop the next URL from the URL stack
            URL url;
            synchronized (urls) {
                if (urls.empty()) {
                    return null;
                } else {
                    url = urls.pop();
                }
            }
            // Skip this URL if it already has a Loader. (Loader
            // may be null in the case where URL has not been opened
            // but is referenced by a JAR index.)
            String urlNoFragString = URLUtil.urlNoFragString(url);
            if (lmap.containsKey(urlNoFragString)) {
                continue;
            }
            // Otherwise, create a new Loader for the URL.
            Loader loader;
            try {
                loader = getLoader(url);
                // If the loader defines a local class path then add the
                // URLs to the list of URLs to be opened.
                URL[] urls = loader.getClassPath();
                if (urls != null) {
                    push(urls);
                }
            } catch (IOException e) {
                // Silently ignore for now...
                continue;
            } catch (SecurityException se) {
                // Always silently ignore. The context, if there is one, that
                // this URLClassPath was given during construction will never
                // have permission to access the URL.
                if (DEBUG) {
                    System.err.println("Failed to access " + url + ", " + se );
                }
                continue;
            }
            // Finally, add the Loader to the search path.
            validateLookupCache(loaders.size(), urlNoFragString);
            loaders.add(loader);
            lmap.put(urlNoFragString, loader);
        }
        if (DEBUG_LOOKUP_CACHE) {
            System.out.println("NOCACHE: Loading from : " + index );
        }
        return loaders.get(index);
    }

    /*
     * Returns the Loader for the specified base URL.
     */
    private Loader getLoader(final URL url) throws IOException {
        try {
            return java.security.AccessController.doPrivileged(
                new java.security.PrivilegedExceptionAction<Loader>() {
                public Loader run() throws IOException {
                    String file = url.getFile();
                    if (file != null && file.endsWith("/")) {
                        if ("file".equals(url.getProtocol())) {
                            return new FileLoader(url);
                        } else {
                            return new Loader(url);
                        }
                    } else {
                        return new JarLoader(url, jarHandler, lmap, acc);
                    }
                }
            }, acc);
        } catch (java.security.PrivilegedActionException pae) {
            throw (IOException)pae.getException();
        }
    }

    /*
     * Pushes the specified URLs onto the list of unopened URLs.
     */
    private void push(URL[] us) {
        synchronized (urls) {
            for (int i = us.length - 1; i >= 0; --i) {
                urls.push(us[i]);
            }
        }
    }

    Convert class path specification into an array of file URLs.
The path of the file is encoded before conversion into URL
form so that reserved characters can safely appear in the path.
/**
     * Convert class path specification into an array of file URLs.
     *
     * The path of the file is encoded before conversion into URL
     * form so that reserved characters can safely appear in the path.
     */
    public static URL[] pathToURLs(String path) {
        StringTokenizer st = new StringTokenizer(path, File.pathSeparator);
        URL[] urls = new URL[st.countTokens()];
        int count = 0;
        while (st.hasMoreTokens()) {
            File f = new File(st.nextToken());
            try {
                f = new File(f.getCanonicalPath());
            } catch (IOException x) {
                // use the non-canonicalized filename
            }
            try {
                urls[count++] = ParseUtil.fileToEncodedURL(f);
            } catch (IOException x) { }
        }

        if (urls.length != count) {
            URL[] tmp = new URL[count];
            System.arraycopy(urls, 0, tmp, 0, count);
            urls = tmp;
        }
        return urls;
    }

    /*
     * Check whether the resource URL should be returned.
     * Return null on security check failure.
     * Called by java.net.URLClassLoader.
     */
    public URL checkURL(URL url) {
        try {
            check(url);
        } catch (Exception e) {
            return null;
        }

        return url;
    }

    /*
     * Check whether the resource URL should be returned.
     * Throw exception on failure.
     * Called internally within this file.
     */
    static void check(URL url) throws IOException {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            URLConnection urlConnection = url.openConnection();
            Permission perm = urlConnection.getPermission();
            if (perm != null) {
                try {
                    security.checkPermission(perm);
                } catch (SecurityException se) {
                    // fallback to checkRead/checkConnect for pre 1.2
                    // security managers
                    if ((perm instanceof java.io.FilePermission) &&
                        perm.getActions().indexOf("read") != -1) {
                        security.checkRead(perm.getName());
                    } else if ((perm instanceof
                        java.net.SocketPermission) &&
                        perm.getActions().indexOf("connect") != -1) {
                        URL locUrl = url;
                        if (urlConnection instanceof JarURLConnection) {
                            locUrl = ((JarURLConnection)urlConnection).getJarFileURL();
                        }
                        security.checkConnect(locUrl.getHost(),
                                              locUrl.getPort());
                    } else {
                        throw se;
                    }
                }
            }
        }
    }

    Inner class used to represent a loader of resources and classes
from a base URL.
/**
     * Inner class used to represent a loader of resources and classes
     * from a base URL.
     */
    private static class Loader implements Closeable {
        private final URL base;
        private JarFile jarfile; // if this points to a jar file

        /*
         * Creates a new Loader for the specified URL.
         */
        Loader(URL url) {
            base = url;
        }

        /*
         * Returns the base URL for this Loader.
         */
        URL getBaseURL() {
            return base;
        }

        URL findResource(final String name, boolean check) {
            URL url;
            try {
                url = new URL(base, ParseUtil.encodePath(name, false));
            } catch (MalformedURLException e) {
                throw new IllegalArgumentException("name");
            }

            try {
                if (check) {
                    URLClassPath.check(url);
                }

                /*
                 * For a HTTP connection we use the HEAD method to
                 * check if the resource exists.
                 */
                URLConnection uc = url.openConnection();
                if (uc instanceof HttpURLConnection) {
                    HttpURLConnection hconn = (HttpURLConnection)uc;
                    hconn.setRequestMethod("HEAD");
                    if (hconn.getResponseCode() >= HttpURLConnection.HTTP_BAD_REQUEST) {
                        return null;
                    }
                } else {
                    // our best guess for the other cases
                    uc.setUseCaches(false);
                    InputStream is = uc.getInputStream();
                    is.close();
                }
                return url;
            } catch (Exception e) {
                return null;
            }
        }

        Resource getResource(final String name, boolean check) {
            final URL url;
            try {
                url = new URL(base, ParseUtil.encodePath(name, false));
            } catch (MalformedURLException e) {
                throw new IllegalArgumentException("name");
            }
            final URLConnection uc;
            try {
                if (check) {
                    URLClassPath.check(url);
                }
                uc = url.openConnection();
                InputStream in = uc.getInputStream();
                if (uc instanceof JarURLConnection) {
                    /* Need to remember the jar file so it can be closed
                     * in a hurry.
                     */
                    JarURLConnection juc = (JarURLConnection)uc;
                    jarfile = JarLoader.checkJar(juc.getJarFile());
                }
            } catch (Exception e) {
                return null;
            }
            return new Resource() {
                public String getName() { return name; }
                public URL getURL() { return url; }
                public URL getCodeSourceURL() { return base; }
                public InputStream getInputStream() throws IOException {
                    return uc.getInputStream();
                }
                public int getContentLength() throws IOException {
                    return uc.getContentLength();
                }
            };
        }

        /*
         * Returns the Resource for the specified name, or null if not
         * found or the caller does not have the permission to get the
         * resource.
         */
        Resource getResource(final String name) {
            return getResource(name, true);
        }

        /*
         * close this loader and release all resources
         * method overridden in sub-classes
         */
        public void close () throws IOException {
            if (jarfile != null) {
                jarfile.close();
            }
        }

        /*
         * Returns the local class path for this loader, or null if none.
         */
        URL[] getClassPath() throws IOException {
            return null;
        }
    }

    /*
     * Inner class used to represent a Loader of resources from a JAR URL.
     */
    static class JarLoader extends Loader {
        private JarFile jar;
        private final URL csu;
        private JarIndex index;
        private MetaIndex metaIndex;
        private URLStreamHandler handler;
        private final HashMap<String, Loader> lmap;
        private final AccessControlContext acc;
        private boolean closed = false;
        private static final sun.misc.JavaUtilZipFileAccess zipAccess =
                sun.misc.SharedSecrets.getJavaUtilZipFileAccess();

        /*
         * Creates a new JarLoader for the specified URL referring to
         * a JAR file.
         */
        JarLoader(URL url, URLStreamHandler jarHandler,
                  HashMap<String, Loader> loaderMap,
                  AccessControlContext acc)
            throws IOException
        {
            super(new URL("jar", "", -1, url + "!/", jarHandler));
            csu = url;
            handler = jarHandler;
            lmap = loaderMap;
            this.acc = acc;

            if (!isOptimizable(url)) {
                ensureOpen();
            } else {
                 String fileName = url.getFile();
                if (fileName != null) {
                    fileName = ParseUtil.decode(fileName);
                    File f = new File(fileName);
                    metaIndex = MetaIndex.forJar(f);
                    // If the meta index is found but the file is not
                    // installed, set metaIndex to null. A typical
                    // senario is charsets.jar which won't be installed
                    // when the user is running in certain locale environment.
                    // The side effect of null metaIndex will cause
                    // ensureOpen get called so that IOException is thrown.
                    if (metaIndex != null && !f.exists()) {
                        metaIndex = null;
                    }
                }

                // metaIndex is null when either there is no such jar file
                // entry recorded in meta-index file or such jar file is
                // missing in JRE. See bug 6340399.
                if (metaIndex == null) {
                    ensureOpen();
                }
            }
        }

        @Override
        public void close () throws IOException {
            // closing is synchronized at higher level
            if (!closed) {
                closed = true;
                // in case not already open.
                ensureOpen();
                jar.close();
            }
        }

        JarFile getJarFile () {
            return jar;
        }

        private boolean isOptimizable(URL url) {
            return "file".equals(url.getProtocol());
        }

        private void ensureOpen() throws IOException {
            if (jar == null) {
                try {
                    java.security.AccessController.doPrivileged(
                        new java.security.PrivilegedExceptionAction<Void>() {
                            public Void run() throws IOException {
                                if (DEBUG) {
                                    System.err.println("Opening " + csu);
                                    Thread.dumpStack();
                                }

                                jar = getJarFile(csu);
                                index = JarIndex.getJarIndex(jar, metaIndex);
                                if (index != null) {
                                    String[] jarfiles = index.getJarFiles();
                                // Add all the dependent URLs to the lmap so that loaders
                                // will not be created for them by URLClassPath.getLoader(int)
                                // if the same URL occurs later on the main class path.  We set
                                // Loader to null here to avoid creating a Loader for each
                                // URL until we actually need to try to load something from them.
                                    for(int i = 0; i < jarfiles.length; i++) {
                                        try {
                                            URL jarURL = new URL(csu, jarfiles[i]);
                                            // If a non-null loader already exists, leave it alone.
                                            String urlNoFragString = URLUtil.urlNoFragString(jarURL);
                                            if (!lmap.containsKey(urlNoFragString)) {
                                                lmap.put(urlNoFragString, null);
                                            }
                                        } catch (MalformedURLException e) {
                                            continue;
                                        }
                                    }
                                }
                                return null;
                            }
                        }, acc);
                } catch (java.security.PrivilegedActionException pae) {
                    throw (IOException)pae.getException();
                }
            }
        }

        /* Throws if the given jar file is does not start with the correct LOC */
        static JarFile checkJar(JarFile jar) throws IOException {
            if (System.getSecurityManager() != null && !DISABLE_JAR_CHECKING
                && !zipAccess.startsWithLocHeader(jar)) {
                IOException x = new IOException("Invalid Jar file");
                try {
                    jar.close();
                } catch (IOException ex) {
                    x.addSuppressed(ex);
                }
                throw x;
            }

            return jar;
        }

        private JarFile getJarFile(URL url) throws IOException {
            // Optimize case where url refers to a local jar file
            if (isOptimizable(url)) {
                FileURLMapper p = new FileURLMapper (url);
                if (!p.exists()) {
                    throw new FileNotFoundException(p.getPath());
                }
                return checkJar(new JarFile(p.getPath()));
            }
            URLConnection uc = getBaseURL().openConnection();
            uc.setRequestProperty(USER_AGENT_JAVA_VERSION, JAVA_VERSION);
            JarFile jarFile = ((JarURLConnection)uc).getJarFile();
            return checkJar(jarFile);
        }

        /*
         * Returns the index of this JarLoader if it exists.
         */
        JarIndex getIndex() {
            try {
                ensureOpen();
            } catch (IOException e) {
                throw new InternalError(e);
            }
            return index;
        }

        /*
         * Creates the resource and if the check flag is set to true, checks if
         * is its okay to return the resource.
         */
        Resource checkResource(final String name, boolean check,
            final JarEntry entry) {

            final URL url;
            try {
                url = new URL(getBaseURL(), ParseUtil.encodePath(name, false));
                if (check) {
                    URLClassPath.check(url);
                }
            } catch (MalformedURLException e) {
                return null;
                // throw new IllegalArgumentException("name");
            } catch (IOException e) {
                return null;
            } catch (AccessControlException e) {
                return null;
            }

            return new Resource() {
                public String getName() { return name; }
                public URL getURL() { return url; }
                public URL getCodeSourceURL() { return csu; }
                public InputStream getInputStream() throws IOException
                    { return jar.getInputStream(entry); }
                public int getContentLength()
                    { return (int)entry.getSize(); }
                public Manifest getManifest() throws IOException {
                    SharedSecrets.javaUtilJarAccess().ensureInitialization(jar);
                    return jar.getManifest();
                }
                public Certificate[] getCertificates()
                    { return entry.getCertificates(); };
                public CodeSigner[] getCodeSigners()
                    { return entry.getCodeSigners(); };
            };
        }


        /*
         * Returns true iff atleast one resource in the jar file has the same
         * package name as that of the specified resource name.
         */
        boolean validIndex(final String name) {
            String packageName = name;
            int pos;
            if((pos = name.lastIndexOf("/")) != -1) {
                packageName = name.substring(0, pos);
            }

            String entryName;
            ZipEntry entry;
            Enumeration<JarEntry> enum_ = jar.entries();
            while (enum_.hasMoreElements()) {
                entry = enum_.nextElement();
                entryName = entry.getName();
                if((pos = entryName.lastIndexOf("/")) != -1)
                    entryName = entryName.substring(0, pos);
                if (entryName.equals(packageName)) {
                    return true;
                }
            }
            return false;
        }

        /*
         * Returns the URL for a resource with the specified name
         */
        URL findResource(final String name, boolean check) {
            Resource rsc = getResource(name, check);
            if (rsc != null) {
                return rsc.getURL();
            }
            return null;
        }

        /*
         * Returns the JAR Resource for the specified name.
         */
        Resource getResource(final String name, boolean check) {
            if (metaIndex != null) {
                if (!metaIndex.mayContain(name)) {
                    return null;
                }
            }

            try {
                ensureOpen();
            } catch (IOException e) {
                throw new InternalError(e);
            }
            final JarEntry entry = jar.getJarEntry(name);
            if (entry != null)
                return checkResource(name, check, entry);

            if (index == null)
                return null;

            HashSet<String> visited = new HashSet<String>();
            return getResource(name, check, visited);
        }

        /*
         * Version of getResource() that tracks the jar files that have been
         * visited by linking through the index files. This helper method uses
         * a HashSet to store the URLs of jar files that have been searched and
         * uses it to avoid going into an infinite loop, looking for a
         * non-existent resource
         */
        Resource getResource(final String name, boolean check,
                             Set<String> visited) {

            Resource res;
            String[] jarFiles;
            int count = 0;
            LinkedList<String> jarFilesList = null;

            /* If there no jar files in the index that can potential contain
             * this resource then return immediately.
             */
            if((jarFilesList = index.get(name)) == null)
                return null;

            do {
                int size = jarFilesList.size();
                jarFiles = jarFilesList.toArray(new String[size]);
                /* loop through the mapped jar file list */
                while(count < size) {
                    String jarName = jarFiles[count++];
                    JarLoader newLoader;
                    final URL url;

                    try{
                        url = new URL(csu, jarName);
                        String urlNoFragString = URLUtil.urlNoFragString(url);
                        if ((newLoader = (JarLoader)lmap.get(urlNoFragString)) == null) {
                            /* no loader has been set up for this jar file
                             * before
                             */
                            newLoader = AccessController.doPrivileged(
                                new PrivilegedExceptionAction<JarLoader>() {
                                    public JarLoader run() throws IOException {
                                        return new JarLoader(url, handler,
                                            lmap, acc);
                                    }
                                }, acc);

                            /* this newly opened jar file has its own index,
                             * merge it into the parent's index, taking into
                             * account the relative path.
                             */
                            JarIndex newIndex = newLoader.getIndex();
                            if(newIndex != null) {
                                int pos = jarName.lastIndexOf("/");
                                newIndex.merge(this.index, (pos == -1 ?
                                    null : jarName.substring(0, pos + 1)));
                            }

                            /* put it in the global hashtable */
                            lmap.put(urlNoFragString, newLoader);
                        }
                    } catch (java.security.PrivilegedActionException pae) {
                        continue;
                    } catch (MalformedURLException e) {
                        continue;
                    }


                    /* Note that the addition of the url to the list of visited
                     * jars incorporates a check for presence in the hashmap
                     */
                    boolean visitedURL = !visited.add(URLUtil.urlNoFragString(url));
                    if (!visitedURL) {
                        try {
                            newLoader.ensureOpen();
                        } catch (IOException e) {
                            throw new InternalError(e);
                        }
                        final JarEntry entry = newLoader.jar.getJarEntry(name);
                        if (entry != null) {
                            return newLoader.checkResource(name, check, entry);
                        }

                        /* Verify that at least one other resource with the
                         * same package name as the lookedup resource is
                         * present in the new jar
                         */
                        if (!newLoader.validIndex(name)) {
                            /* the mapping is wrong */
                            throw new InvalidJarIndexException("Invalid index");
                        }
                    }

                    /* If newLoader is the current loader or if it is a
                     * loader that has already been searched or if the new
                     * loader does not have an index then skip it
                     * and move on to the next loader.
                     */
                    if (visitedURL || newLoader == this ||
                            newLoader.getIndex() == null) {
                        continue;
                    }

                    /* Process the index of the new loader
                     */
                    if((res = newLoader.getResource(name, check, visited))
                            != null) {
                        return res;
                    }
                }
                // Get the list of jar files again as the list could have grown
                // due to merging of index files.
                jarFilesList = index.get(name);

            // If the count is unchanged, we are done.
            } while(count < jarFilesList.size());
            return null;
        }


        /*
         * Returns the JAR file local class path, or null if none.
         */
        URL[] getClassPath() throws IOException {
            if (index != null) {
                return null;
            }

            if (metaIndex != null) {
                return null;
            }

            ensureOpen();
            parseExtensionsDependencies();

            if (SharedSecrets.javaUtilJarAccess().jarFileHasClassPathAttribute(jar)) { // Only get manifest when necessary
                Manifest man = jar.getManifest();
                if (man != null) {
                    Attributes attr = man.getMainAttributes();
                    if (attr != null) {
                        String value = attr.getValue(Name.CLASS_PATH);
                        if (value != null) {
                            return parseClassPath(csu, value);
                        }
                    }
                }
            }
            return null;
        }

        /*
         * parse the standard extension dependencies
         */
        private void  parseExtensionsDependencies() throws IOException {
            ExtensionDependency.checkExtensionsDependencies(jar);
        }

        /*
         * Parses value of the Class-Path manifest attribute and returns
         * an array of URLs relative to the specified base URL.
         */
        private URL[] parseClassPath(URL base, String value)
            throws MalformedURLException
        {
            StringTokenizer st = new StringTokenizer(value);
            URL[] urls = new URL[st.countTokens()];
            int i = 0;
            while (st.hasMoreTokens()) {
                String path = st.nextToken();
                URL url = DISABLE_CP_URL_CHECK ? new URL(base, path) : tryResolve(base, path);
                if (url != null) {
                    urls[i] = url;
                    i++;
                } else {
                    if (DEBUG_CP_URL_CHECK) {
                        System.err.println("Class-Path entry: \"" + path
                                           + "\" ignored in JAR file " + base);
                    }
                }
            }
            if (i == 0) {
                urls = null;
            } else if (i != urls.length) {
                // Truncate nulls from end of array
                urls = Arrays.copyOf(urls, i);
            }
            return urls;
        }

        static URL tryResolve(URL base, String input) throws MalformedURLException {
            if ("file".equalsIgnoreCase(base.getProtocol())) {
                return tryResolveFile(base, input);
            } else {
                return tryResolveNonFile(base, input);
            }
        }

        Attempt to return a file URL by resolving input against a base file
URL. The input is an absolute or relative file URL that encodes a
file path.
Throws: MalformedURLException – 
API Note: Nonsensical input such as a Windows file path with a drive
letter cannot be disambiguated from an absolute URL so will be rejected
(by returning null) by this method.
Returns: the resolved URL or null if the input is an absolute URL with
        a scheme other than file (ignoring case)/**
         * Attempt to return a file URL by resolving input against a base file
         * URL. The input is an absolute or relative file URL that encodes a
         * file path.
         *
         * @apiNote Nonsensical input such as a Windows file path with a drive
         * letter cannot be disambiguated from an absolute URL so will be rejected
         * (by returning null) by this method.
         *
         * @return the resolved URL or null if the input is an absolute URL with
         *         a scheme other than file (ignoring case)
         * @throws MalformedURLException
         */
        static URL tryResolveFile(URL base, String input) throws MalformedURLException {
            int index = input.indexOf(':');
            boolean isFile;
            if (index >= 0) {
                String scheme = input.substring(0, index);
                isFile = "file".equalsIgnoreCase(scheme);
            } else {
                isFile = true;
            }
            return (isFile) ? new URL(base, input) : null;
        }

        Attempt to return a URL by resolving input against a base URL. Returns
null if the resolved URL is not contained by the base URL.
Throws: MalformedURLException – 
Returns: the resolved URL or null/**
         * Attempt to return a URL by resolving input against a base URL. Returns
         * null if the resolved URL is not contained by the base URL.
         *
         * @return the resolved URL or null
         * @throws MalformedURLException
         */
        static URL tryResolveNonFile(URL base, String input) throws MalformedURLException {
            String child = input.replace(File.separatorChar, '/');
            if (isRelative(child)) {
                URL url = new URL(base, child);
                String bp = base.getPath();
                String urlp = url.getPath();
                int pos = bp.lastIndexOf('/');
                if (pos == -1) {
                    pos = bp.length() - 1;
                }
                if (urlp.regionMatches(0, bp, 0, pos + 1)
                        && urlp.indexOf("..", pos) == -1) {
                    return url;
                }
            }
            return null;
        }

        Returns true if the given input is a relative URI.
/**
         * Returns true if the given input is a relative URI.
         */
        static boolean isRelative(String child) {
            try {
                return !URI.create(child).isAbsolute();
            } catch (IllegalArgumentException e) {
                return false;
            }
        }
    }

    /*
     * Inner class used to represent a loader of classes and resources
     * from a file URL that refers to a directory.
     */
    private static class FileLoader extends Loader {
        /* Canonicalized File */
        private File dir;

        FileLoader(URL url) throws IOException {
            super(url);
            if (!"file".equals(url.getProtocol())) {
                throw new IllegalArgumentException("url");
            }
            String path = url.getFile().replace('/', File.separatorChar);
            path = ParseUtil.decode(path);
            dir = (new File(path)).getCanonicalFile();
        }

        /*
         * Returns the URL for a resource with the specified name
         */
        URL findResource(final String name, boolean check) {
            Resource rsc = getResource(name, check);
            if (rsc != null) {
                return rsc.getURL();
            }
            return null;
        }

        Resource getResource(final String name, boolean check) {
            final URL url;
            try {
                URL normalizedBase = new URL(getBaseURL(), ".");
                url = new URL(getBaseURL(), ParseUtil.encodePath(name, false));

                if (url.getFile().startsWith(normalizedBase.getFile()) == false) {
                    // requested resource had ../..'s in path
                    return null;
                }

                if (check)
                    URLClassPath.check(url);

                final File file;
                if (name.indexOf("..") != -1) {
                    file = (new File(dir, name.replace('/', File.separatorChar)))
                          .getCanonicalFile();
                    if ( !((file.getPath()).startsWith(dir.getPath())) ) {
                        /* outside of base dir */
                        return null;
                    }
                } else {
                    file = new File(dir, name.replace('/', File.separatorChar));
                }

                if (file.exists()) {
                    return new Resource() {
                        public String getName() { return name; };
                        public URL getURL() { return url; };
                        public URL getCodeSourceURL() { return getBaseURL(); };
                        public InputStream getInputStream() throws IOException
                            { return new FileInputStream(file); };
                        public int getContentLength() throws IOException
                            { return (int)file.length(); };
                    };
                }
            } catch (Exception e) {
                return null;
            }
            return null;
        }
    }
}
Params:	name – the name of the resource check – whether to perform a security check
Returns:	a `URL` for the resource, or `null` if the resource could not be found.
Params:	name – the resource name
Returns:	an Enumeration of all the urls having the specified name
Throws:	MalformedURLException –
API Note:	Nonsensical input such as a Windows file path with a drive letter cannot be disambiguated from an absolute URL so will be rejected (by returning null) by this method.
Returns:	the resolved URL or null if the input is an absolute URL with a scheme other than file (ignoring case)
/

java/ 8/ sun/misc/URLClassPath.java
