How to download a file from Google Cloud Storage with Java?

Question

I\'m developping an application that provides users with an interface where they can download files from our Google Cloud Storage. I wrote unit tests and I could connect to

Answer 1

With the latest libraries :

Storage storage = StorageOptions.newBuilder()
            .setProjectId(projectId)
            .setCredentials(GoogleCredentials.fromStream(new FileInputStream(serviceAccountJSON)))
            .build()
            .getService();
Blob blob = storage.get(BUCKET_URL, RELATIVE_OBJECT_LOCATION);
ReadChannel readChannel = blob.reader();
FileOutputStream fileOutputStream = new FileOutputStream(outputFileName);
fileOutputStream.getChannel().transferFrom(readChannel, 0, Long.MAX_VALUE);
fileOutputStream.close();

Answer 2

As you say, currently you're downloading the metadata. You need to use media download to download the object's data.

Take a look at the sample Java code here: https://developers.google.com/storage/docs/json_api/v1/objects/get

That is the simplest method, using getMediaHttpDownloader().

There is more info on media and the other method, resumable download, here: https://code.google.com/p/google-api-java-client/wiki/MediaDownload

Answer 3

@AnandMohan is correct. You just have to make copy on "tmp" folder because all the locations are read only, just "tmp" is writable. Check below:

    Storage storage = StorageOptions.newBuilder().setProjectId(PROJECT_ID).build().getService();
    Blob blob = storage.get(BUCKET_NAME, fileName);
    ReadChannel readChannel = blob.reader();
    File file = new File("/tmp/" + FILE_NAME);
    FileOutputStream fileOuputStream = new FileOutputStream(file);
    fileOuputStream.getChannel().transferFrom(readChannel, 0, Long.MAX_VALUE);
    fileOuputStream.close();
    // Now file is ready to send whereever you want