[JAVA] [Note] Download from S3, upload to S3

1. File download from S3 This time, I described the case of downloading all the files under the target path of the bucket.

  AmazonS3 s3Client = AmazonS3ClientBuilder.standard().withRegion("Region name").build();

  //Get the list of files under the bucket on S3
  ObjectListing objListing = s3Client.listObjects("Bucket name");
  List<S3ObjectSummary> objList = objListing.getObjectSummaries();

  try {
    //Process files on S3
    for (S3ObjectSummary obj : objList) {
      //Since objList contains all folders and file information under the bucket, it is necessary to narrow down by the target path.
      //Do not download if the target path is not included or the size is 0
      if (!StringUtils.contains(obj.getKey(), "Target path") || obj.getSize() == 0) {
        continue;
      }

      //Download process below
      // obj.getKey()Is"Target path/file name"Has become
      GetObjectRequest request = new GetObjectRequest("Bucket name", obj.getKey());
      //Only the file name
      String fileName = obj.getKey().replace("Target path", "");
      //Generate download destination file
      File file = new File(fileName);
      if (s3Client.getObject(request, file) == null) {
        //Download failure
      }
    }
  } catch (IOException e) {
    throw e;
  }

2. Upload to S3 When uploading a file to the target path under the bucket

  try {
    AmazonS3 s3Client = AmazonS3ClientBuilder.standard().withRegion("Region name").build();

    File file = new File("File name to be uploaded");
    PutObjectRequest request = new PutObjectRequest("Bucket name", "Target path" + file.getName(), file);
    request.setCannedAcl(CannedAccessControlList.PublicRead);
    s3Client.putObject(request);
  } catch (Exception e) {
    throw e;
  }