JDK14/Java14源码在线阅读

/*
 * Copyright (c) 1997, 2013, 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.net.www.protocol.jar;

import java.io.IOException;
import java.io.FileNotFoundException;
import java.net.URL;
import java.net.URLConnection;
import java.util.HashMap;
import java.util.jar.JarFile;
import java.security.Permission;
import sun.net.util.URLUtil;

/* A factory for cached JAR file. This class is used to both retrieve
 * and cache Jar files.
 *
 * @author Benjamin Renaud
 * @since 1.2
 */
class JarFileFactory implements URLJarFile.URLJarFileCloseController {

    /* the url to file cache */
    private static final HashMap<String, JarFile> fileCache = new HashMap<>();

    /* the file to url cache */
    private static final HashMap<JarFile, URL> urlCache = new HashMap<>();

    private static final JarFileFactory instance = new JarFileFactory();

    private JarFileFactory() { }

    public static JarFileFactory getInstance() {
        return instance;
    }

    URLConnection getConnection(JarFile jarFile) throws IOException {
        URL u;
        synchronized (instance) {
            u = urlCache.get(jarFile);
        }
        if (u != null)
            return u.openConnection();

        return null;
    }

    public JarFile get(URL url) throws IOException {
        return get(url, true);
    }

    JarFile get(URL url, boolean useCaches) throws IOException {

        JarFile result;
        JarFile local_result;

        if (useCaches) {
            synchronized (instance) {
                result = getCachedJarFile(url);
            }
            if (result == null) {
                local_result = URLJarFile.getJarFile(url, this);
                synchronized (instance) {
                    result = getCachedJarFile(url);
                    if (result == null) {
                        fileCache.put(urlKey(url), local_result);
                        urlCache.put(local_result, url);
                        result = local_result;
                    } else {
                        if (local_result != null) {
                            local_result.close();
                        }
                    }
                }
            }
        } else {
            result = URLJarFile.getJarFile(url, this);
        }
        if (result == null)
            throw new FileNotFoundException(url.toString());

        return result;
    }

    /**
     * Callback method of the URLJarFileCloseController to
     * indicate that the JarFile is close. This way we can
     * remove the JarFile from the cache
     */
    public void close(JarFile jarFile) {
        synchronized (instance) {
            URL urlRemoved = urlCache.remove(jarFile);
            if (urlRemoved != null)
                fileCache.remove(urlKey(urlRemoved));
        }
    }

    private JarFile getCachedJarFile(URL url) {
        assert Thread.holdsLock(instance);
        JarFile result = fileCache.get(urlKey(url));

        /* if the JAR file is cached, the permission will always be there */
        if (result != null) {
            Permission perm = getPermission(result);
            if (perm != null) {
                SecurityManager sm = System.getSecurityManager();
                if (sm != null) {
                    try {
                        sm.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) {
                            sm.checkRead(perm.getName());
                        } else if ((perm instanceof
                            java.net.SocketPermission) &&
                            perm.getActions().indexOf("connect") != -1) {
                            sm.checkConnect(url.getHost(), url.getPort());
                        } else {
                            throw se;
                        }

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