Get Google Cloud Storage object list in Java

Introduction

How to get the Google Cloud Storage object list in Java.

I had a hard time finding a simple way to authenticate or get only a specific directory: tired_face:

build.gradle Just google-cloud-storage is OK.

build.gradle

apply plugin: 'java'
apply plugin: 'application'

repositories {
  mavenCentral()
}

dependencies {
    compile 'com.google.cloud:google-cloud-storage:0.9.4-beta'
}

mainClassName = "GCSList"

run {
    if (project.hasProperty('args')) {
        args project.args.split('\\s+')
    }
}

code

Code that outputs a list to objects under a specific directory.

You can now specify the JSON Key path for the service account as a command line argument. If there is no argument, the default account will be used. [^ 1]

[^ 1]: Something like gcloud auth login

src/main/java/GCSList.java

import com.google.auth.oauth2.ServiceAccountCredentials;
import com.google.cloud.Page;
import com.google.cloud.storage.Blob;
import com.google.cloud.storage.Bucket;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;

import java.io.*;
import java.util.Iterator;

public class GCSList {
    private static final String BUCKET = "mybucket";
    private static final String PREFIX = "dir1/dir2/";

    public static void main(String args[]) throws IOException {
        Storage storage;
        if (args.length > 0) {
            storage = getStorageFromJsonKey(args[0]);
        } else {
            storage = StorageOptions.getDefaultInstance().getService();
        }

        Bucket bucket = storage.get(BUCKET);

        //Narrow down to specific directories
        Storage.BlobListOption option = Storage.BlobListOption.prefix(PREFIX);

        Page<Blob> blobs = bucket.list(option);
        Iterator<Blob> blobIterator = blobs.iterateAll();

        while (blobIterator.hasNext()) {
            System.out.println(blobIterator.next().getName());
        }
    }

    private static Storage getStorageFromJsonKey(String key) throws IOException {
        return StorageOptions.newBuilder()
                .setCredentials(ServiceAccountCredentials.fromStream(new FileInputStream(key)))
                .build()
                .getService();
    }
}

Run

When using JSON Key

$ ./gradlew run -Pargs="/path/to/key.json"

When not in use

$ ./gradlew run

in conclusion

The code for this time is here: pencil: https://github.com/nownabe/examples/tree/master/list-gcs-java