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Google Cloud Java Client for Storage

Java idiomatic client for Google Cloud Storage.

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Quickstart

If you are using Maven, add this to your pom.xml file

<dependency>
  <groupId>com.google.cloud</groupId>
  <artifactId>google-cloud-storage</artifactId>
  <version>1.15.0</version>
</dependency>

If you are using Gradle, add this to your dependencies

compile 'com.google.cloud:google-cloud-storage:1.15.0'

If you are using SBT, add this to your dependencies

libraryDependencies += "com.google.cloud" % "google-cloud-storage" % "1.15.0"

Example Applications

  • StorageExample is a simple command line interface that provides some of Cloud Storage's functionality. Read more about using the application on the StorageExample docs page.
  • Bookshelf - An App Engine app that manages a virtual bookshelf.
    • This app uses google-cloud to interface with Cloud Datastore and Cloud Storage. It also uses Cloud SQL, another Google Cloud Platform service.
  • Flexible Environment/Storage example - An app that uploads files to a public Cloud Storage bucket on the App Engine Flexible Environment runtime.

Authentication

See the Authentication section in the base directory's README.

About Google Cloud Storage

Google Cloud Storage is a durable and highly available object storage service. Google Cloud Storage is almost infinitely scalable and guarantees consistency: when a write succeeds, the latest copy of the object will be returned to any GET, globally.

See the Google Cloud Storage docs for more details on how to activate Cloud Storage for your project.

See the Storage client library docs to learn how to interact with the Cloud Storage using this Client Library.

Getting Started

Prerequisites

For this tutorial, you will need a Google Developers Console project with "Google Cloud Storage" and "Google Cloud Storage JSON API" enabled via the console's API Manager. You will need to enable billing to use Google Cloud Storage. Follow these instructions to get your project set up. You will also need to set up the local development environment by installing the Google Cloud SDK and running the following commands in command line: gcloud auth login and gcloud config set project [YOUR PROJECT ID].

Installation and setup

You'll need to obtain the google-cloud-storage library. See the Quickstart section to add google-cloud-storage as a dependency in your code.

Creating an authorized service object

To make authenticated requests to Google Cloud Storage, you must create a service object with credentials. You can then make API calls by calling methods on the Storage service object. The simplest way to authenticate is to use Application Default Credentials. These credentials are automatically inferred from your environment, so you only need the following code to create your service object:

import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;

Storage storage = StorageOptions.getDefaultInstance().getService();

For other authentication options, see the Authentication page.

Storing data

Stored objects are called "blobs" in google-cloud and are organized into containers called "buckets". Blob, a subclass of BlobInfo, adds a layer of service-related functionality over BlobInfo. Similarly, Bucket adds a layer of service-related functionality over BucketInfo. In this code snippet, we will create a new bucket and upload a blob to that bucket.

Add the following imports at the top of your file:

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.cloud.storage.Blob;
import com.google.cloud.storage.Bucket;
import com.google.cloud.storage.BucketInfo;

Then add the following code to create a bucket and upload a simple blob.

Important: Bucket names have to be globally unique (among all users of Cloud Storage). If you choose a bucket name that already exists, you'll get a helpful error message telling you to choose another name. In the code below, replace "my_unique_bucket" with a unique bucket name. See more about naming rules here.

// Create a bucket
String bucketName = "my_unique_bucket"; // Change this to something unique
Bucket bucket = storage.create(BucketInfo.of(bucketName));

// Upload a blob to the newly created bucket
BlobId blobId = BlobId.of(bucketName, "my_blob_name");
BlobInfo blobInfo = BlobInfo.newBuilder(blobId).setContentType("text/plain").build();
Blob blob = storage.create(blobInfo, "a simple blob".getBytes(UTF_8));

A complete example for creating a blob can be found at CreateBlob.java.

At this point, you will be able to see your newly created bucket and blob on the Google Developers Console.

Retrieving data

Now that we have content uploaded to the server, we can see how to read data from the server. Add the following line to your program to get back the blob we uploaded.

BlobId blobId = BlobId.of(bucketName, "my_blob_name");
byte[] content = storage.readAllBytes(blobId);
String contentString = new String(content, UTF_8);

A complete example for accessing blobs can be found at CreateBlob.java.

Updating data

Another thing we may want to do is update a blob. The following snippet shows how to update a Storage blob if it exists.

BlobId blobId = BlobId.of(bucketName, "my_blob_name");
Blob blob = storage.get(blobId);
if (blob != null) {
  byte[] prevContent = blob.getContent();
  System.out.println(new String(prevContent, UTF_8));
  WritableByteChannel channel = blob.writer();
  channel.write(ByteBuffer.wrap("Updated content".getBytes(UTF_8)));
  channel.close();
}

The complete source code can be found at UpdateBlob.java.

Listing buckets and contents of buckets

Suppose that you've added more buckets and blobs, and now you want to see the names of your buckets and the contents of each one. Add the following code to list all your buckets and all the blobs inside each bucket.

// List all your buckets
System.out.println("My buckets:");
for (Bucket bucket : storage.list().iterateAll()) {
  System.out.println(bucket);
  
  // List all blobs in the bucket
  System.out.println("Blobs in the bucket:");
  for (Blob blob : bucket.list().iterateAll()) {
    System.out.println(blob);
  }
}

Complete source code

In CreateAndListBucketsAndBlobs.java we put together examples creating and listing buckets and blobs into one program. The program assumes that you are running on Compute Engine or from your own desktop. To run the example on App Engine, simply move the code from the main method to your application's servlet class and change the print statements to display on your webpage.

Troubleshooting

To get help, follow the instructions in the shared Troubleshooting document.

Transport

Storage uses HTTP for the transport layer.

Java Versions

Java 7 or above is required for using this client.

Testing

This library has tools to help make tests for code using Cloud Storage.

See TESTING to read more about testing.

Versioning

This library follows Semantic Versioning.

It is currently in major version one (1.y.z), which means that the public API should be considered stable.

Contributing

Contributions to this library are always welcome and highly encouraged.

See google-cloud's CONTRIBUTING documentation and the shared documentation for more information on how to get started.

Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms. See Code of Conduct for more information.

License

Apache 2.0 - See LICENSE for more information.