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The AWS SDK for Java with support for OSGi. The AWS SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2016-2016 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.AmazonClientException;
import com.amazonaws.SDKGlobalConfiguration;
import com.amazonaws.annotation.SdkInternalApi;
import com.amazonaws.internal.config.Builder;
import com.amazonaws.util.IOUtils;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * A region metadata builder that loads the data by looking at all the
 * legacy metadata locations.
 */
@SdkInternalApi
public class LegacyRegionXmlMetadataBuilder implements Builder {

    private static final String REGIONS_FILE_OVERRIDE =
            SDKGlobalConfiguration.REGIONS_FILE_OVERRIDE_SYSTEM_PROPERTY;

    private static final String OVERRIDE_ENDPOINTS_RESOURCE_PATH =
            "/com/amazonaws/regions/override/regions.xml";

    private static final Log LOG = LogFactory.getLog(LegacyRegionXmlMetadataBuilder.class);

    @Override
    public RegionMetadata build() {
        return loadOverrideMetadataIfExists();
    }

    private RegionMetadata loadOverrideMetadataIfExists() {
        RegionMetadata metadata = loadFromSystemProperty();

        if (metadata == null) {
            InputStream override = RegionUtils.class
                    .getResourceAsStream(OVERRIDE_ENDPOINTS_RESOURCE_PATH);
            if (override != null) {
                metadata = loadFromStream(override);
                IOUtils.closeQuietly(override, LOG);
            }
        }

        return metadata;
    }

    /**
     * Loads region metadata from file location specified in
     * {@link #REGIONS_FILE_OVERRIDE} property.
     * Returns null if no such property exists.
     *
     * @throws AmazonClientException if any error occurs while loading the
     *                               metadata file.
     */
    private RegionMetadata loadFromSystemProperty() {
        final String overrideFilePath = System.getProperty
                (REGIONS_FILE_OVERRIDE);

        if (overrideFilePath != null) {
            try {
                return LegacyRegionXmlLoadUtils.load(new File
                        (overrideFilePath));
            } catch (IOException exception) {
                throw new AmazonClientException(
                        "Error parsing region metadata from " + overrideFilePath,
                        exception);
            }
        }
        return null;
    }

    /**
     * Loads region metadata from file location specified in
     * {@link #REGIONS_FILE_OVERRIDE} property.
     * Returns null if no such property exists.
     *
     * @throws AmazonClientException if any error occurs while loading the
     *                               metadata file.
     */
    private RegionMetadata loadFromStream(final InputStream stream) {
        try {
            return LegacyRegionXmlLoadUtils.load(stream);
        } catch (IOException exception) {
            throw new AmazonClientException(
                    "Error parsing region metadata from input stream",
                    exception);
        }
    }
}