org.apache.hadoop.crypto.key.KeyProviderFactory.java Source code

Introduction

Here is the source code for org.apache.hadoop.crypto.key.KeyProviderFactory.java

Source

/**
 * 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.hadoop.crypto.key;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.ServiceLoader;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.CommonConfigurationKeysPublic;

/**
 * A factory to create a list of KeyProvider based on the path given in a
 * Configuration. It uses a service loader interface to find the available
 * KeyProviders and create them based on the list of URIs.
 */
@InterfaceAudience.Public
@InterfaceStability.Unstable
public abstract class KeyProviderFactory {
    public static final String KEY_PROVIDER_PATH = CommonConfigurationKeysPublic.HADOOP_SECURITY_KEY_PROVIDER_PATH;

    public abstract KeyProvider createProvider(URI providerName, Configuration conf) throws IOException;

    private static final ServiceLoader<KeyProviderFactory> serviceLoader = ServiceLoader
            .load(KeyProviderFactory.class, KeyProviderFactory.class.getClassLoader());

    // Iterate through the serviceLoader to avoid lazy loading.
    // Lazy loading would require synchronization in concurrent use cases.
    static {
        Iterator<KeyProviderFactory> iterServices = serviceLoader.iterator();
        while (iterServices.hasNext()) {
            iterServices.next();
        }
    }

    public static List<KeyProvider> getProviders(Configuration conf) throws IOException {
        List<KeyProvider> result = new ArrayList<KeyProvider>();
        for (String path : conf.getStringCollection(KEY_PROVIDER_PATH)) {
            try {
                URI uri = new URI(path);
                KeyProvider kp = get(uri, conf);
                if (kp != null) {
                    result.add(kp);
                } else {
                    throw new IOException("No KeyProviderFactory for " + uri + " in " + KEY_PROVIDER_PATH);
                }
            } catch (URISyntaxException error) {
                throw new IOException("Bad configuration of " + KEY_PROVIDER_PATH + " at " + path, error);
            }
        }
        return result;
    }

    /**
     * Create a KeyProvider based on a provided URI.
     *
     * @param uri key provider URI
     * @param conf configuration to initialize the key provider
     * @return the key provider for the specified URI, or <code>NULL</code> if
     *         a provider for the specified URI scheme could not be found.
     * @throws IOException thrown if the provider failed to initialize.
     */
    public static KeyProvider get(URI uri, Configuration conf) throws IOException {
        KeyProvider kp = null;
        for (KeyProviderFactory factory : serviceLoader) {
            kp = factory.createProvider(uri, conf);
            if (kp != null) {
                break;
            }
        }
        return kp;
    }

}