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'rapiddweller Common' is an open source Java library forked from Databene Commons by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * 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.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.rapiddweller.common.web;

import com.rapiddweller.common.IOUtil;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import java.io.File;
import java.io.IOException;
import java.net.URL;

/**
 * Provides file download and caches files in the file system.
 * Created: 15.08.2010 10:07:24
 *
 * @author Volker Bergmann
 * @since 0.5.4
 */
public class DownloadCache {

  private static final String DEFAULT_ROOT_FOLDER = "./cache";

  private static final Logger LOGGER = LogManager.getLogger(DownloadCache.class);

  private final File rootFolder;

  /**
   * Instantiates a new Download cache.
   */
  public DownloadCache() {
    this(new File(DEFAULT_ROOT_FOLDER));
  }

  /**
   * Instantiates a new Download cache.
   *
   * @param rootFolder the root folder
   */
  public DownloadCache(File rootFolder) {
    this.rootFolder = rootFolder;
  }

  /**
   * Get.
   *
   * @param url the url
   * @throws IOException the io exception
   */
  public void get(URL url) throws IOException {
    File cacheSubDir = new File(rootFolder, url.getHost());
    String filename = url.getFile();
    if (filename.endsWith("/")) {
      filename = filename.substring(0, filename.length() - 1) + ".dir";
    }
    File cacheFile = new File(cacheSubDir, filename);
    if (!cacheFile.exists()) {
      IOUtil.download(url, cacheFile);
    } else {
      LOGGER.info("providing {} from cache file {}", url, cacheFile.getAbsolutePath());
    }
  }

}