Downloader.java

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.LocalDateTime;
import java.util.Base64;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import static java.net.http.HttpResponse.BodyHandlers.ofInputStream;
import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;
import static java.time.ZoneId.systemDefault;
import static java.time.format.DateTimeFormatter.ofPattern;

public class Downloader {

    public static void main(String[] args) {

        if(args.length != 4) {
            
            System.out.println();
            System.out.println("Usage: java Downloader.java [username] [password] [endpoint] [destFolder]");
            System.out.println("Note: enclose argument in single quotes if using special characters on zsh");
            System.out.println();
            
            return;
        }

        var username = args[0];
        var password = args[1];
        var endpoint = args[2];
        var destFolder = args[3];

        ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
        scheduler.scheduleAtFixedRate(() -> downloadFile(username, password, endpoint, destFolder), 0, 6, TimeUnit.HOURS);

    }

    public static void downloadFile(String username, String password, String endpoint, String destFolder) {

        String date = LocalDateTime.now(systemDefault()).format(ofPattern("yyyy-MM-dd-HH-mm-ss"));
        String filename = String.format("download-"+username+"-%s.csv", date);
        Path destinationFile = Paths.get(destFolder, filename);
        
        String auth = username + ":" + password;
        String authHeader = "Basic " + new String(Base64.getEncoder().encode(auth.getBytes()));

        HttpClient client = HttpClient.newBuilder()
                .version(HttpClient.Version.HTTP_1_1)
                .followRedirects(HttpClient.Redirect.NORMAL)
                .build();

        try {
            System.out.println(LocalDateTime.now(systemDefault()) + " Calling to " + endpoint);

            HttpRequest request = HttpRequest.newBuilder()
                    .GET()
                    .uri(new URI(endpoint))
                    .header("Authorization", authHeader)
                    .build();

            var response = client.send(request, ofInputStream());

            if (response.statusCode() == 200) {
                System.out.println(LocalDateTime.now(systemDefault()) + " Writing to " + destinationFile.toFile().getAbsolutePath());
                Files.copy(response.body(), destinationFile, REPLACE_EXISTING);
                System.out.println(LocalDateTime.now(systemDefault()) + " Done.");
            }
            else {
                throw new IOException("Received status code " + response.statusCode());
            }
        }
        catch (URISyntaxException | IOException | InterruptedException e) {
            e.printStackTrace();
        }

    }

}