org.apache.hadoop.security.alias.CredentialProviderFactory.java Source code

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Here is the source code for org.apache.hadoop.security.alias.CredentialProviderFactory.java

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/**
 * 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.security.alias;

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 CredentialProvider based on the path given in a
 * Configuration. It uses a service loader interface to find the available
 * CredentialProviders and create them based on the list of URIs.
 */
@InterfaceAudience.Public
@InterfaceStability.Unstable
public abstract class CredentialProviderFactory {
    public static final String CREDENTIAL_PROVIDER_PATH = CommonConfigurationKeysPublic.HADOOP_SECURITY_CREDENTIAL_PROVIDER_PATH;

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

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

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

    public static List<CredentialProvider> getProviders(Configuration conf) throws IOException {
        List<CredentialProvider> result = new ArrayList<CredentialProvider>();
        for (String path : conf.getStringCollection(CREDENTIAL_PROVIDER_PATH)) {
            try {
                URI uri = new URI(path);
                boolean found = false;
                // Iterate serviceLoader in a synchronized block since
                // serviceLoader iterator is not thread-safe.
                synchronized (serviceLoader) {
                    for (CredentialProviderFactory factory : serviceLoader) {
                        CredentialProvider kp = factory.createProvider(uri, conf);
                        if (kp != null) {
                            result.add(kp);
                            found = true;
                            break;
                        }
                    }
                }
                if (!found) {
                    throw new IOException(
                            "No CredentialProviderFactory for " + uri + " in " + CREDENTIAL_PROVIDER_PATH);
                }
            } catch (URISyntaxException error) {
                throw new IOException("Bad configuration of " + CREDENTIAL_PROVIDER_PATH + " at " + path, error);
            }
        }
        return result;
    }
}