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Java example source code file (FtpClientProvider.java)

This example Java source code file (FtpClientProvider.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

class, classnotfoundexception, ftpclientprovider, illegalaccessexception, instantiationexception, object, privilegedaction, runtimepermission, security, securityexception, securitymanager, string, util

The FtpClientProvider.java Java example source code

/*
 * Copyright (c) 2009, 2011, 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.ftp;

import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ServiceConfigurationError;
//import java.util.ServiceLoader;

/**
 * Service provider class for FtpClient.
 * Sub-classes of FtpClientProvider provide an implementation of {@link FtpClient}
 * and associated classes. Applications do not normally use this class directly.
 * See {@link #provider() } for how providers are found and loaded.
 *
 * @since 1.7
 */
public abstract class FtpClientProvider {

    /**
     * Creates a FtpClient from this provider.
     *
     * @return The created {@link FtpClient}.
     */
    public abstract FtpClient createFtpClient();
    private static final Object lock = new Object();
    private static FtpClientProvider provider = null;

    /**
     * Initializes a new instance of this class.
     *
     * @throws SecurityException if a security manager is installed and it denies
     *         {@link RuntimePermission}<tt>("ftpClientProvider")
     */
    protected FtpClientProvider() {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(new RuntimePermission("ftpClientProvider"));
        }
    }

    private static boolean loadProviderFromProperty() {
        String cm = System.getProperty("sun.net.ftpClientProvider");
        if (cm == null) {
            return false;
        }
        try {
            Class<?> c = Class.forName(cm, true, null);
            provider = (FtpClientProvider) c.newInstance();
            return true;
        } catch (ClassNotFoundException |
                 IllegalAccessException |
                 InstantiationException |
                 SecurityException x) {
            throw new ServiceConfigurationError(x.toString());
        }
    }

    private static boolean loadProviderAsService() {
//        Iterator<FtpClientProvider> i =
//                ServiceLoader.load(FtpClientProvider.class,
//                                   ClassLoader.getSystemClassLoader()).iterator();
//
//        while (i.hasNext()) {
//            try {
//                provider = i.next();
//                return true;
//            } catch (ServiceConfigurationError sce) {
//                if (sce.getCause() instanceof SecurityException) {
//                    // Ignore, try next provider, if any
//                    continue;
//                }
//                throw sce;
//            }
//        }
        return false;
    }

    /**
     * Returns the system wide default FtpClientProvider for this invocation of
     * the Java virtual machine.
     *
     * <p> The first invocation of this method locates the default provider
     * object as follows: </p>
     *
     * <ol>
     *
     *   <li>

If the system property * <tt>java.net.FtpClientProvider is defined then it is * taken to be the fully-qualified name of a concrete provider class. * The class is loaded and instantiated; if this process fails then an * unspecified unchecked error or exception is thrown. </p> * * <li>

If a provider class has been installed in a jar file that is * visible to the system class loader, and that jar file contains a * provider-configuration file named * <tt>java.net.FtpClientProvider in the resource * directory <tt>META-INF/services, then the first class name * specified in that file is taken. The class is loaded and * instantiated; if this process fails then an unspecified unchecked error or exception is * thrown. </p> * * <li>

Finally, if no provider has been specified by any of the above * means then the system-default provider class is instantiated and the * result is returned. </p> * * </ol> * * <p> Subsequent invocations of this method return the provider that was * returned by the first invocation. </p> * * @return The system-wide default FtpClientProvider */ public static FtpClientProvider provider() { synchronized (lock) { if (provider != null) { return provider; } return (FtpClientProvider) AccessController.doPrivileged( new PrivilegedAction<Object>() { public Object run() { if (loadProviderFromProperty()) { return provider; } if (loadProviderAsService()) { return provider; } provider = new sun.net.ftp.impl.DefaultFtpClientProvider(); return provider; } }); } } }

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