Java tutorial
/* * Copyright 2011-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Licensed under the Apache License, Version 2.0 (the "License"). * You may not use this file except in compliance with the License. * A copy of the License is located at * * http://aws.amazon.com/apache2.0 * * or in the "license" file accompanying this file. This file 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 com.amazonaws.regions; import com.amazonaws.SdkClientException; import com.amazonaws.auth.AWSCredentialsProviderChain; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import java.util.ArrayList; import java.util.Collections; import java.util.List; /** * Composite {@link AwsRegionProvider} that sequentially delegates to a chain of providers looking * for region information. */ public class AwsRegionProviderChain extends AwsRegionProvider { private static final Log LOG = LogFactory.getLog(AWSCredentialsProviderChain.class); private final List<AwsRegionProvider> providers; public AwsRegionProviderChain(AwsRegionProvider... providers) { this.providers = new ArrayList<AwsRegionProvider>(providers.length); Collections.addAll(this.providers, providers); } @Override public String getRegion() throws SdkClientException { for (AwsRegionProvider provider : providers) { try { final String region = provider.getRegion(); if (region != null) { return region; } } catch (Exception e) { // Ignore any exceptions and move onto the next provider LOG.debug("Unable to load region from " + provider.toString() + ": " + e.getMessage()); } } // Note: This is a bug in the provider chain. The chain should return null when no region is found according to // the interface, but an exception is thrown here instead. This class is used in too many places to change now. // TODO: In 2.0, be sure this bug does not carry through. throw new SdkClientException("Unable to load region information from any provider in the chain"); } }