org.apache.hadoop.fs.s3a.AWSCredentialProviderList.java Source code

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Here is the source code for org.apache.hadoop.fs.s3a.AWSCredentialProviderList.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.fs.s3a;

import com.amazonaws.AmazonClientException;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.AWSCredentialsProvider;
import com.amazonaws.auth.AnonymousAWSCredentials;
import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

/**
 * A list of providers.
 *
 * This is similar to the AWS SDK {@code AWSCredentialsProviderChain},
 * except that:
 * <ol>
 *   <li>Allows extra providers to be added dynamically.</li>
 *   <li>If any provider in the chain throws an exception other than
 *   an {@link AmazonClientException}, that is rethrown, rather than
 *   swallowed.</li>
 *   <li>Has some more diagnostics.</li>
 *   <li>On failure, the last AmazonClientException raised is rethrown.</li>
 *   <li>Special handling of {@link AnonymousAWSCredentials}.</li>
 * </ol>
 */
@InterfaceAudience.Private
@InterfaceStability.Evolving
public class AWSCredentialProviderList implements AWSCredentialsProvider {

    private static final Logger LOG = LoggerFactory.getLogger(AWSCredentialProviderList.class);
    public static final String NO_AWS_CREDENTIAL_PROVIDERS = "No AWS Credential Providers";

    private final List<AWSCredentialsProvider> providers = new ArrayList<>(1);
    private boolean reuseLastProvider = true;
    private AWSCredentialsProvider lastProvider;

    /**
     * Empty instance. This is not ready to be used.
     */
    public AWSCredentialProviderList() {
    }

    /**
     * Create with an initial list of providers.
     * @param providers provider list.
     */
    public AWSCredentialProviderList(Collection<AWSCredentialsProvider> providers) {
        this.providers.addAll(providers);
    }

    /**
     * Add a new provider.
     * @param p provider
     */
    public void add(AWSCredentialsProvider p) {
        providers.add(p);
    }

    /**
     * Reuse the last provider?
     * @param reuseLastProvider flag to indicate the last provider should
     * be re-used
     */
    public void setReuseLastProvider(boolean reuseLastProvider) {
        this.reuseLastProvider = reuseLastProvider;
    }

    /**
     * query the {@link #reuseLastProvider} flag.
     * @return the current flag state.
     */
    public boolean isReuseLastProvider() {
        return reuseLastProvider;
    }

    /**
     * Refresh all child entries.
     */
    @Override
    public void refresh() {
        for (AWSCredentialsProvider provider : providers) {
            provider.refresh();
        }
    }

    /**
     * Iterate through the list of providers, to find one with credentials.
     * If {@link #reuseLastProvider} is true, then it is re-used.
     * @return a set of credentials (possibly anonymous), for authenticating.
     */
    @Override
    public AWSCredentials getCredentials() {
        checkNotEmpty();
        if (reuseLastProvider && lastProvider != null) {
            return lastProvider.getCredentials();
        }

        AmazonClientException lastException = null;
        for (AWSCredentialsProvider provider : providers) {
            try {
                AWSCredentials credentials = provider.getCredentials();
                if ((credentials.getAWSAccessKeyId() != null && credentials.getAWSSecretKey() != null)
                        || (credentials instanceof AnonymousAWSCredentials)) {
                    lastProvider = provider;
                    LOG.debug("Using credentials from {}", provider);
                    return credentials;
                }
            } catch (AmazonClientException e) {
                lastException = e;
                LOG.debug("No credentials provided by {}: {}", provider, e.toString(), e);
            }
        }

        // no providers had any credentials. Rethrow the last exception
        // or create a new one.
        String message = "No AWS Credentials provided by " + listProviderNames();
        if (lastException != null) {
            message += ": " + lastException;
        }
        throw new AmazonClientException(message, lastException);

    }

    /**
     * Verify that the provider list is not empty.
     * @throws AmazonClientException if there are no providers.
     */
    public void checkNotEmpty() {
        if (providers.isEmpty()) {
            throw new AmazonClientException(NO_AWS_CREDENTIAL_PROVIDERS);
        }
    }

    /**
     * List all the providers' names.
     * @return a list of names, separated by spaces (with a trailing one).
     * If there are no providers, "" is returned.
     */
    public String listProviderNames() {
        StringBuilder sb = new StringBuilder(providers.size() * 32);
        for (AWSCredentialsProvider provider : providers) {
            sb.append(provider.getClass().getSimpleName());
            sb.append(' ');
        }
        return sb.toString();
    }

    /**
     * The string value is this class name and the string values of nested
     * providers.
     * @return a string value for debugging.
     */
    @Override
    public String toString() {
        return "AWSCredentialProviderList: " + StringUtils.join(providers, " ");
    }
}