How to download the response file which is in zip format for a GET https request using Java. In postman the response is some junk character

I am using Java for this to create a connection HttpURLConnection but not sure how to download the response.

When I checked for the header fields from response, below are the details I found

> {null=[HTTP/1.1 200 OK], Server=[Apigee LB], Access-Control-Allow-Origin=[*], Access-Control-Allow-Methods=[GET, PUT, POST, DELETE], Content-Disposition=[attachment; filename="OfflineQueryResult-2ba8631e-c542-49f0-9012-32875875d5f8.zip"], Connection=[keep-alive], Content-Length=[265], Access-Control-Max-Age=[3628800], Date=[Sun, 23 Aug 2020 10:15:42 GMT], Access-Control-Allow-Headers=[origin, x-requested-with, accept], Content-Type=[text/xml]}>

Here in the above object (higlighted), there is a filename inside the Content-Disposition, that filename I should be able to download automatically to the local folder or path

Can someone please help here

If you’re using Java 11 or later, you don’t need HttpURLConnection at all. You can use the java.net.http package:

URL url = /* ... */;

Path downloadDir = Path.of(System.getProperty("user.home"), "Downloads");

HttpResponse<Path> response = HttpClient.newHttpClient().send(
    HttpRequest.newBuilder(url.toURI()).GET().build(),
    HttpResponse.BodyHandlers.ofFileDownload(downloadDir));

Path downloadedFile = response.body();

If you’re using a version of Java older than 11, you can obtain the disposition header using the getHeaderField method. And you can download using Files.copy.

HttpURLConnection conn = /* ... */;

Path downloadDir = Paths.get(System.getProperty("user.home"), "Downloads");

Path downloadedFile = null;
String disposition = conn.getHeaderField("Content-Disposition");
if (disposition != null) {
    String filenameIndex = disposition.indexOf("filename=");
    if (filenameIndex >= 0) {
        String filename = disposition.substring(filenameIndex + 9);
        if (filename.startsWith("\"")) {
            // filename is everything inside double-quotes.
            int endIndex = filename.indexOf('"', 1);
            filename = filename.substring(1, endIndex);
        } else {
            // filename is unquoted and goes until ';' or end of string.
            int endIndex = filename.indexOf(';');
            if (endIndex > 0 ) {
                filename = filename.substring(0, endIndex);
            }
        }
        downloadedFile = downloadDir.resolve(filename);
    }
}
if (downloadedFile == null) {
    downloadedFile = Files.createTempFile(downloadDir, null, null);
}

try (InputStream urlStream = conn.getInputStream()) {
    Files.copy(urlStream, downloadedFile,
        StandardCopyOption.REPLACE_EXISTING);
}

You can use JAX-RS Client API to consume the ZIP response :

Client client = ClientBuilder.newClient();
InputStream is = client.target("http://host:port")
                       .path("api").path("API-Path")
                       .request().accept("application/zip")
                       .get(InputStream.class);

ZipInputStream zis = new ZipInputStream(is);
zis.getNextEntry();

// Print in console
Scanner sc = new Scanner(zis);
while (sc.hasNextLine()) {
    System.out.println(sc.nextLine());
}

To download using HttpURLConnection, you use

HttpURLConnection myConnection = ...;
InputStream stream = myConnection.getInputStream();

Then you need to suck up all the bytes from the stream. Basically, you create a read buffer (byte), call read(byte[]) on the InputStream, and then dump those bytes into a larger buffer, possibly a ByteBuffer object, until there is nothing left to read (read returns -1). Also, you can plug in DataFetcher to do the above for you