001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.security.alias;
020
021import java.io.IOException;
022import java.net.URI;
023import java.net.URISyntaxException;
024import java.util.ArrayList;
025import java.util.List;
026import java.util.ServiceLoader;
027
028import org.apache.hadoop.classification.InterfaceAudience;
029import org.apache.hadoop.classification.InterfaceStability;
030import org.apache.hadoop.conf.Configuration;
031
032/**
033 * A factory to create a list of CredentialProvider based on the path given in a
034 * Configuration. It uses a service loader interface to find the available
035 * CredentialProviders and create them based on the list of URIs.
036 */
037@InterfaceAudience.Public
038@InterfaceStability.Unstable
039public abstract class CredentialProviderFactory {
040  public static final String CREDENTIAL_PROVIDER_PATH =
041      "hadoop.security.credential.provider.path";
042
043  public abstract CredentialProvider createProvider(URI providerName,
044                                             Configuration conf
045                                             ) throws IOException;
046
047  private static final ServiceLoader<CredentialProviderFactory> serviceLoader =
048      ServiceLoader.load(CredentialProviderFactory.class);
049
050  public static List<CredentialProvider> getProviders(Configuration conf
051                                               ) throws IOException {
052    List<CredentialProvider> result = new ArrayList<CredentialProvider>();
053    for(String path: conf.getStringCollection(CREDENTIAL_PROVIDER_PATH)) {
054      try {
055        URI uri = new URI(path);
056        boolean found = false;
057        for(CredentialProviderFactory factory: serviceLoader) {
058          CredentialProvider kp = factory.createProvider(uri, conf);
059          if (kp != null) {
060            result.add(kp);
061            found = true;
062            break;
063          }
064        }
065        if (!found) {
066          throw new IOException("No CredentialProviderFactory for " + uri + " in " +
067              CREDENTIAL_PROVIDER_PATH);
068        }
069      } catch (URISyntaxException error) {
070        throw new IOException("Bad configuration of " + CREDENTIAL_PROVIDER_PATH +
071            " at " + path, error);
072      }
073    }
074    return result;
075  }
076}