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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 2013-2016 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.services.s3.transfer;

import static com.amazonaws.util.StringUtils.UTF8;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import com.amazonaws.util.json.Jackson;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * Abstract base class for the information of a pausible upload or download; such
 * information can be used to resume the upload or download later on, and can be
 * serialized/deserialized for persistence purposes.
 */
public abstract class PersistableTransfer {

    private static final ObjectMapper MAPPER = new ObjectMapper();

    /**
     * Returns the serialized representation of the paused transfer state.
     */
    public final String serialize() {
        return Jackson.toJsonString(this);
    }

    /**
     * Writes the serialized representation of the paused transfer state to the
     * given OutputStream. Caller of this method should explicitly
     * close the OutputStream.
     */
    public final void serialize(OutputStream out) throws IOException {
        out.write(Jackson.toJsonString(this).getBytes(UTF8));
        out.flush();
    }

    /**
     * Returns the deserialized transfer state of the given serialized
     * representation. Caller of this method should explicitly close the
     * InputStream.
     *
     * @throws UnsupportedOperationException
     *             if the paused transfer type extracted from the serialized
     *             representation is not supported.
     */
    public static  T deserializeFrom(InputStream in) {
        String type;
        JsonNode tree;
        try {
            tree = MAPPER.readTree(in);
            JsonNode pauseType = tree.get("pauseType");
            if (pauseType == null)
                throw new IllegalArgumentException(
                        "Unrecognized serialized state");
            type = pauseType.asText();
        } catch (Exception e) {
            throw new IllegalArgumentException(e);
        }
        Class clazz;
        if (PersistableDownload.TYPE.equals(type)) {
            clazz = PersistableDownload.class;
        } else if (PersistableUpload.TYPE.equals(type)) {
            clazz = PersistableUpload.class;
        } else {
            throw new UnsupportedOperationException(
                    "Unsupported paused transfer type: " + type);
        }
        try {
            @SuppressWarnings("unchecked")
            T t = (T) MAPPER.treeToValue(tree, clazz);
            return t;
        } catch (JsonProcessingException e) {
            throw new IllegalStateException(e);
        }
    }

    /**
     * Returns the deserialized transfer state of the given serialized
     * representation.
     *
     * @throws UnsupportedOperationException
     *             if the paused transfer type extracted from the serialized
     *             representation is not supported.
     */
    public static  T deserializeFrom(
            String serialized) {
        if (serialized == null)
            return null;
        ByteArrayInputStream byteStream = new ByteArrayInputStream(
                serialized.getBytes(UTF8));
        try{
            return deserializeFrom(byteStream);
        }finally{
            try { byteStream.close(); } catch(IOException ioe) { } ;
        }
    }
}