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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.partitions;

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

import com.amazonaws.AmazonClientException;
import com.amazonaws.annotation.SdkInternalApi;
import com.amazonaws.partitions.model.Partitions;
import com.amazonaws.regions.RegionMetadata;
import com.amazonaws.util.IOUtils;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.MapperFeature;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * Loads all the partition files into memory.
 */
@SdkInternalApi
public class PartitionsLoader {

    /**
     * class path from where all partition files are loaded.
     */
    public static final String PARTITIONS_RESOURCE_PATH =
            "com/amazonaws/partitions/endpoints.json";

    /**
     * override class path from where all partition files are loaded.
     */
    public static final String PARTITIONS_OVERRIDE_RESOURCE_PATH =
            "com/amazonaws/partitions/override/endpoints.json";

    /**
     * Jackson object mapper that is used for parsing the partition files.
     */
    private static final ObjectMapper mapper = new ObjectMapper()
            .disable(MapperFeature.CAN_OVERRIDE_ACCESS_MODIFIERS)
            .disable(MapperFeature.ALLOW_FINAL_FIELDS_AS_MUTATORS)
            .enable(JsonParser.Feature.ALLOW_COMMENTS)
            .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);

    /**
     * classloader to to be used for loading the partitions.
     */
    private final ClassLoader classLoader;

    public PartitionsLoader() {
        this.classLoader = PartitionsLoader.class.getClassLoader();
    }

    /**
     * Loads the partition files from the {@link #PARTITIONS_OVERRIDE_RESOURCE_PATH}. If no files are present, then
     * loads the partition files from the {@link #PARTITIONS_RESOURCE_PATH}
     * 
     * Builds the {@link RegionMetadata} from the partition files.
     */
    public PartitionMetadataProvider build() {

        InputStream stream = classLoader
                .getResourceAsStream(PARTITIONS_OVERRIDE_RESOURCE_PATH);

        if (stream != null) {
            return new PartitionMetadataProvider(loadPartitionFromStream(stream, PARTITIONS_OVERRIDE_RESOURCE_PATH).getPartitions());
        } else {
            stream = classLoader.getResourceAsStream(PARTITIONS_RESOURCE_PATH);
            if (stream == null) {
                throw new AmazonClientException("Unable to load parition metadata from " + PARTITIONS_RESOURCE_PATH);
            }
            return new PartitionMetadataProvider(loadPartitionFromStream(stream, PARTITIONS_RESOURCE_PATH).getPartitions());
        }
    }

    private Partitions loadPartitionFromStream(InputStream stream, String location) {

        try {

            return mapper.readValue(stream, Partitions.class);

        } catch (IOException e) {
            throw new AmazonClientException("Error while loading partitions " +
                    "file from " + location, e);
        } finally {
            IOUtils.closeQuietly(stream, null);
        }
    }
}