public String generateURL(final String documentName, final boolean fileAttached) {
   if (fileAttached) {
     GeneratePresignedUrlRequest urlRequest =
         new GeneratePresignedUrlRequest(S3_BUCKET, documentName);
     urlRequest.setMethod(HttpMethod.GET);
     Calendar calendar = new GregorianCalendar();
     calendar.add(Calendar.MONTH, 1);
     Date nextMonth = calendar.getTime();
     urlRequest.setExpiration(nextMonth);
     URL url = s3client.generatePresignedUrl(urlRequest);
     return url.toString();
   } else {
     return "No File Attached";
   }
 }
  public static String xs3_generate_url(String xs3_objname, String content_type) {
    AWSCredentials xs3_credentials = new BasicAWSCredentials(xs3_access_key, xs3_secret_key);
    ClientConfiguration xs3_clientconfig = new ClientConfiguration();
    xs3_clientconfig.setProtocol(Protocol.HTTP);

    S3ClientOptions xs3_client_options = new S3ClientOptions();
    xs3_client_options.setPathStyleAccess(true);

    xs3_client = new AmazonS3Client(xs3_credentials, xs3_clientconfig);
    xs3_client.setEndpoint(xs3_endpoint);
    xs3_client.setS3ClientOptions(xs3_client_options);

    try {
      java.util.Date expiration = new java.util.Date();

      long milliSeconds = expiration.getTime();
      milliSeconds += 1000 * 60 * 5;
      expiration.setTime(milliSeconds);

      GeneratePresignedUrlRequest xs3_genurl_req =
          new GeneratePresignedUrlRequest(xs3_bucketname, xs3_objname);
      xs3_genurl_req.setMethod(HttpMethod.PUT);
      xs3_genurl_req.setExpiration(expiration);
      xs3_genurl_req.setContentType(content_type);
      xs3_genurl_req.addRequestParameter("x-amz-acl", "public-read");

      URL url = xs3_client.generatePresignedUrl(xs3_genurl_req);

      System.out.println(url.toString());
      return url.toString();

    } catch (AmazonServiceException ase) {
      System.out.println("xs3_svr_error_message:" + ase.getMessage());
      System.out.println("xs3_svr_status_code:  " + ase.getStatusCode());
      System.out.println("xs3_svr_error_code:   " + ase.getErrorCode());
      System.out.println("xs3_svr_error_type:   " + ase.getErrorType());
      System.out.println("xs3_svr_request_id:   " + ase.getRequestId());
    } catch (AmazonClientException ace) {
      System.out.println("xs3_clt_error_message:" + ace.getMessage());
    }

    return null;
  }
  public static String gen_part_url(
      String uploadId, int file_size, String file_name, String file_type) {
    AWSCredentials xs3_credentials = new BasicAWSCredentials(xs3_access_key, xs3_secret_key);
    ClientConfiguration xs3_clientconfig = new ClientConfiguration();
    xs3_clientconfig.setProtocol(Protocol.HTTP);

    S3ClientOptions xs3_client_options = new S3ClientOptions();
    xs3_client_options.setPathStyleAccess(true);

    xs3_client = new AmazonS3Client(xs3_credentials, xs3_clientconfig);
    xs3_client.setEndpoint(xs3_endpoint);
    xs3_client.setS3ClientOptions(xs3_client_options);

    try {

      final int xs3_part_size = 1024 * 1024 * 5;

      int xs3_part_count = (int) Math.ceil((double) (file_size) / (double) xs3_part_size);
      JSONArray jsonArray = new JSONArray();
      JSONObject jsonObject_1 = new JSONObject();
      jsonObject_1.put("total_num", xs3_part_count);
      jsonObject_1.put("upload_id", uploadId);

      JSONArray jsonArray_sub = new JSONArray();
      for (int part_no = 0; part_no < xs3_part_count; part_no++) {

        long xs3_offset_bytes = xs3_part_size * part_no;

        long part_size =
            xs3_part_size < (file_size - xs3_offset_bytes)
                ? xs3_part_size
                : (file_size - xs3_offset_bytes);

        java.util.Date expiration = new java.util.Date();
        long milliSeconds = expiration.getTime();
        milliSeconds += 1000 * 60 * 5;
        expiration.setTime(milliSeconds);

        GeneratePresignedUrlRequest xs3_genurl_req =
            new GeneratePresignedUrlRequest(xs3_bucketname, file_name);
        xs3_genurl_req.setMethod(HttpMethod.PUT);
        xs3_genurl_req.setExpiration(expiration);
        xs3_genurl_req.setContentType(file_type);
        xs3_genurl_req.addRequestParameter("uploadId", uploadId);
        xs3_genurl_req.addRequestParameter("partNumber", String.valueOf(part_no + 1));

        URL url = xs3_client.generatePresignedUrl(xs3_genurl_req);
        System.out.println(url.toString());

        JSONObject jsonObject = new JSONObject();
        jsonObject.put("part_idx", part_no);
        jsonObject.put("part_url", url.toString());
        jsonObject.put("upload_len", part_size);
        jsonObject.put("part_begin", xs3_offset_bytes);
        jsonObject.put("part_end", xs3_offset_bytes + part_size);

        jsonArray_sub.add(jsonObject);
      }

      jsonObject_1.put("multi_list", jsonArray_sub);
      jsonArray.add(jsonObject_1);

      return jsonArray.toString();

    } catch (AmazonServiceException ase) {
      System.out.println("xs3_svr_error_message:" + ase.getMessage());
      System.out.println("xs3_svr_status_code:  " + ase.getStatusCode());
      System.out.println("xs3_svr_error_code:   " + ase.getErrorCode());
      System.out.println("xs3_svr_error_type:   " + ase.getErrorType());
      System.out.println("xs3_svr_request_id:   " + ase.getRequestId());
    } catch (AmazonClientException ace) {
      System.out.println("xs3_clt_error_message:" + ace.getMessage());
    }

    return null;
  }