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Gobblin Ingestion Framework

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/*
 * Copyright (C) 2014-2016 LinkedIn Corp. 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. 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.
 */
package gobblin.source.extractor.filebased;

import java.io.IOException;
import java.util.Iterator;

import gobblin.configuration.ConfigurationKeys;


/**
 * An abstraction for downloading a file in a {@link FileBasedExtractor}. Subclasses are expected to download the file in
 * the {@link #downloadFile(String)} method and return a record iterator. A {@link FileDownloader} can be set in a
 * {@link FileBasedExtractor} by setting {@link ConfigurationKeys#SOURCE_FILEBASED_OPTIONAL_DOWNLOADER_CLASS} in the
 * state.
 *
 * @param  record type in the file
 */
public abstract class FileDownloader {

  protected final FileBasedExtractor fileBasedExtractor;

  public FileDownloader(FileBasedExtractor fileBasedExtractor) {
    this.fileBasedExtractor = fileBasedExtractor;
  }

  /**
   * Downloads the file at filePath using the {@link FileBasedExtractor#fsHelper} and returns an
   * {@link Iterator} to the records
   *
   * @param filePath of the file to be downloaded
   * @return An iterator to the records in the file
   */
  public abstract Iterator downloadFile(final String filePath) throws IOException;
}