org.uberfire.java.nio.file.api.FileSystemProviders Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of vfs-api
VFS API
The newest version!
/*
 * Copyright 2012 JBoss Inc
 *
 * Licensed 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.uberfire.java.nio.file.api;

import java.net.URI;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;

import org.uberfire.java.nio.file.FileSystemNotFoundException;
import org.uberfire.java.nio.file.spi.FileSystemProvider;

import static java.util.Collections.*;
import static org.uberfire.commons.util.Preconditions.*;

/**
 * Back port of JSR-203 from Java Platform, Standard Edition 7.
 * @see Original JavaDoc
 */
public final class FileSystemProviders {

    // for lazy init
    private static class FileSystemProvidersHolder {

        static List installedProviders = buildProviders();
        static Map mapOfinstalledProviders = buildProvidersMap();

        private synchronized static List buildProviders() {
            final ServiceLoader providers = ServiceLoader.load(FileSystemProvider.class);
            if (providers == null) {
                return emptyList();
            }
            final List result = new ArrayList();

            for (final FileSystemProvider provider : providers) {
                result.add(provider);
            }
            return unmodifiableList(result);
        }

        private synchronized static Map buildProvidersMap() {
            final Map result = new HashMap(installedProviders.size() + 1);
            for (int i = 0; i < installedProviders.size(); i++) {
                final FileSystemProvider provider = installedProviders.get(i);
                if (i == 0) {
                    provider.forceAsDefault();
                    result.put("default", provider);
                }
                result.put(provider.getScheme(), provider);
            }
            return unmodifiableMap(result);
        }
    }

    private FileSystemProviders() {
    }

    /**
     * Non standard method that provides access to default provider (default:// scheme).
     * @return the default file system provider
     * @throws ServiceConfigurationError
     */
    public static FileSystemProvider getDefaultProvider() throws ServiceConfigurationError {
        return FileSystemProvidersHolder.installedProviders.get(0);
    }

    /**
     * Non standard method to resolve a provider based on uri's scheme
     * @param uri the uri
     * @return the file system provider
     */
    public static FileSystemProvider resolveProvider(final URI uri) {
        checkNotNull("uri", uri);

        return getProvider(uri.getScheme());
    }

    private static FileSystemProvider getProvider(final String scheme)
            throws FileSystemNotFoundException, ServiceConfigurationError {
        checkNotEmpty("scheme", scheme);

        final FileSystemProvider fileSystemProvider = FileSystemProvidersHolder.mapOfinstalledProviders.get(scheme);

        if (fileSystemProvider == null) {
            throw new FileSystemNotFoundException("Provider '" + scheme + "' not found");
        }

        return fileSystemProvider;
    }

    /**
     * @throws ServiceConfigurationError
     * @see Original JavaDoc
     */
    public static List installedProviders() throws ServiceConfigurationError {
        return FileSystemProvidersHolder.installedProviders;
    }

}