在 S3 上解压 base64 gzip 并保存到本地文件系统

Question

我是 Java 傻瓜/新手，所以请保持温和。我有两个我意识到有些不兼容的功能：

1. saveS3toFilesystem - 从 AWS S3 获取 InputStream 并将其作为文件保存到本地文件系统
2. decompress - 接受一个字符串并解码 base64 编码并解压缩 gzip 压缩。

我真的希望这两者协同工作以实现保存到文件系统的文件是未压缩文件的结果，但我意识到我的“解压缩”函数可能应该更改为接收流而不是字符串，但遗憾的是这些天来，我只是 Java 世界中的“剪纸师”。

这是我现在的两个函数：

private void saveS3toFilesystem(String filename, String bucketName, String localFilename) {
  S3Object obj = s3.getObject(bucketName, filename);
  InputStream in = obj.getObjectContent();
  try {
    Files.createDirectories(Paths.get(localFilename.replace(this.FILE_EXTENSION, "")));
    Files.copy(in, Paths.get(localFilename));
    this.logger.log("Input file has been placed in local filesystem for ITMS to pick up: " + localFilename + "\n");
  } catch (IOException err) {
    this.logger.log("There was a problem saving the file to " + localFilename);
    err.printStackTrace();
  } finally {
    try {
      in.close();
    } catch (IOException err) {
      err.printStackTrace();
    }
  }
  return;
}

然后……

private String decompress(String compressedZip) {
  byte[] decodedBytes = Base64.getDecoder().decode(compressedZip);
  String result = null;
  GZIPInputStream zip = null;
  try {
    zip = new GZIPInputStream(new ByteArrayInputStream(decodedBytes));
    result = IOUtils.toString(zip);
  } catch (IOException e) {
    e.printStackTrace();
  } finally {
    IOUtils.closeQuietly(zip);
  }
  return result;
}

谁能帮我实现梦想？很高兴使用流、字符串或任何可行的方法来做到这一点。可悲的是，我负担不起 atm 来提高我的 Java 技能以自己摸索解决方案。

非常感谢。

Answer 1

基于以下 API： Base64.Decoder和GZIPInputStream（看前者的wrap方法和后者的构造函数），解压方法可以重载如下：

private String decompress(InputStream compressedStream) {
  InputStream decodingStream = Base64.getDecoder().wrap(compressedStream);
  String result = null;
  GZIPInputStream zip = null;
  try {
    zip = new GZIPInputStream(decodingStream);
    result = IOUtils.toString(zip);
  } catch (IOException e) {
    e.printStackTrace();
  } finally {
    IOUtils.closeQuietly(zip);
  }
  return result;
}

最后，saveS3toFilesystem 的变化如下：

private void saveS3toFilesystem(String filename, String bucketName, String localFilename) {
  S3Object obj = s3.getObject(bucketName, filename);
  InputStream in = obj.getObjectContent();
  // decoding the inputstream via decode into a string, which is then
  // used in order to create an inputstream of decoded data
  InputStream decodedStream = 
     new ByteArrayInputStream(decompress(in).getBytes(StandardCharsets.UTF_8));
  try {
    Files.createDirectories(Paths.get(localFilename.replace(this.FILE_EXTENSION, "")));
    Files.copy(decodedStream, Paths.get(localFilename));
    this.logger.log("Input file has been placed in local filesystem for ITMS to pick up: " + localFilename + "\n");
  } catch (IOException err) {
    this.logger.log("There was a problem saving the file to " + localFilename);
    err.printStackTrace();
  } finally {
    try {
      in.close();
    } catch (IOException err) {
      err.printStackTrace();
    }
  }
  return;
}