Using Google Cloud Storage

Contents

1. Prerequisites and setup

2. Activating a Cloud Storage bucket

   1. Setting bucket and object permissions

3. Downloading the client library

4. Reading and writing to a bucket

5. Using the client library with the development app server

6. Pricing, quotas, and limits

7. Alternatives ways to access Cloud Storage

Prerequisites and setup

You need to complete the following:

1. Follow the instructions in "Hello, World!" for Java on App Engine to set up your environment and project, and to understand how Java apps are structured in App Engine. Write down and save your project ID for use with your application.

2. Activate a Cloud Storage bucket for your app to use, and set permissions if neccessary .

3. Download the client library.

Activating a Cloud Storage bucket

To use Cloud Storage, you'll need to activate at least one bucket. Typically, you might want to use the 5GB free default bucket, and upgrade this into a paid bucket if you need more storage. You can always activate and use other paid bucket if you want, but there is only one free default bucket per project.

To activate the free, default Cloud Storage bucket for your app:

1. Click Create under Default Cloud Storage Bucket in the App Engine settings page for your project. Notice the name of this bucket: it is in the form <project-id>.appspot.com.

2. If you need more storage than the 5GB limit, you can increase this by enabling billing for your project, making this a paid bucket. You will be charged for storage over the 5GB limit.

If you want to activate one or more paid buckets, follow the instructions under Creating a bucket to activate them.

Downloading the client library

You can download the library using popular tools like Apache Maven, Apache Ivy, or Git, or you can download the library manually from the Maven repository. Choose your preferred method:

Reading and writing to a bucket

The following sample shows how to write a file to a Cloud Storage bucket, and how to retrieve a file:

java/example/src/com/google/appengine/demos/GcsExampleServlet.java

View on GitHub

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Notice the sample shows the optional use of the Blobstore API for serving files stored in Cloud Storage. This can be a more cost effective and faster way to return files to the caller because it returns the file to the caller without your app having to read the file. For more information, see Using the Blobstore API with Google Cloud Storage.

Also, notice that the code above shows how to set the retry parameters, which control the retries that occur in case of network or resource issues. Normally, you should not have to set the retry parameters, because the default values will work for the majority of cases.

Using the client library with the development app server

You can use the client library with the development server. This provides Cloud Storage emulation using the local disk.

Note: Files saved locally are subject to the file size and naming conventions imposed by the local filesystem.

Pricing, quotas, and limits

There are no bandwidth charges associated with making Google Cloud Storage client library calls to Cloud Storage. However, there are operations charges; because the calls count against your URL fetch quota, as the library uses the URL Fetch service to interact with Cloud Storage. And There are operations and storage charges, however,

Notice that Google Cloud Storage is a pay-to-use service; you will be charged according to the Cloud Storage price sheet.

Alternatives ways to access Cloud Storage

Instead of using the client library, you could use the following:

• Cloud Storage REST API. This could be a good choice if you need a specific feature not provided in the client library. However, this isn't compatible with the development server.

• Cloud Storage Browser in the Google Cloud Platform Console. Useful for uploading objects quickly.

• gsutil. A command line tool.