# Get started with Java client library

To start using the Google Photos Library API with the Java client library, you will need to
[set up the client library](https://developers.google.com/photos/library/legacy/guides/get-started-java#get-library) in your development environment.
Before you do that, [configure your project](https://developers.google.com/photos/library/legacy/guides/get-started-java#configure-app) by enabling the API
via the Google API Console and setting up an OAuth 2.0 client ID.

Your application interacts with Google Photos on behalf of a
Google Photos user. For instance, when you create albums in a user's
Google Photos library or upload media items to a user's
Google Photos account, the user authorizes these API requests via the
[OAuth 2.0](https://developers.google.com/identity/protocols/OAuth2) protocol.

The OAuth 2.0 client ID allows your application users to sign in, authenticate,
and thereby use the Library API. The Library API does not support
service accounts; to use this API, users must be signed in to a valid Google
Account.

## Configure your app

### Enable the API

Before you can use the Library API, you must enable it for your project.

1. Go to the [Google API Console](https://console.developers.google.com/apis/library).
2. From the menu bar, select a project or create a new project.
3. To open the Google API Library, from the Navigation menu, select **APIs \& Services \> Library**.
4. Search for "Google Photos Library API". Select the correct result and click **Enable**.

### Request an OAuth 2.0 client ID

Follow the steps below to request an OAuth client ID and configure it for your
application. This example uses an application where the entire OAuth flow is
handled server-side, such as the one in our samples. The setup process may vary
for other [implementation scenarios](https://developers.google.com/identity/protocols/OAuth2).

1. Go to the [Google API Console](https://console.developers.google.com/apis/library) and select your project.
2. From the menu, select **APIs \& Services \> Credentials**.
3. On the **Credentials** page, click **Create Credentials \> OAuth client ID**.
4. Select your **Application type** . In this example, the application type is **Web application**.
5. Register the origins from which your app is allowed to access the Google APIs
   as follows:

   1. To identify the client ID, enter a name.
   2. In the **Authorized JavaScript origins** field, enter the origin for your
      app. This field doesn't allow wildcards.

      You can enter multiple origins to allow your app to run on different
      protocols, domains, or subdomains. The URLs you enter are allowed to
      start an OAuth request.

      The following example shows a local development URL (our samples use
      `localhost:8080`) and a production URL.

          http://localhost:8080
          https://myproductionurl.example.com

   3. The **Authorized redirect URI** field is the endpoint that receives
      responses from the OAuth 2.0 server. Typically, this includes your
      development environment and points to a path in your application.

          http://localhost:8080/auth/google/callback
          https://myproductionurl.example.com/auth/google/callback

   4. Click **Create**.

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6. From the resulting OAuth client dialog, download the JSON file
   containing your client configuration. You client details consist of the
   following:

   - Client ID
   - Client secret

   This JSON file will be used later to [set up](https://developers.google.com/photos/library/legacy/guides/get-started-java#get-library)
   the Google Auth library for Java which works with this client library.

Before you can launch a public application that accesses the Library API,
your app must be reviewed by Google. An "Unverified app" message appears on the
screen when you test your application, until it is
[verified](https://support.google.com/cloud/answer/7454865).

## Set up the client library

The Java client library handles all the backend API calls for you, and exposes
friendly objects to work with, including code samples for some common API tasks.
Firstly, download and install the Google Photos Library API client library for Java along
with the dependencies from [GitHub](https://github.com/google/java-photoslibrary).
Then, set up your OAuth2 credentials for Java.

### Download options

Here are some options to download the client library:

- **Gradle dependency:**

  To use this library with Gradle, add the following dependency to your
  `build.gradle` file.

      repositories {
        mavenCentral()
      }
      dependencies {
        compile 'com.google.photos.library:google-photos-library-client:1.7.3'
      }

- **Maven dependency:**

  To use this library with Maven, add the following to your Maven `pom.xml`
  file.

      <dependency>
        <groupId>com.google.photos.library</groupId>
        <artifactId>google-photos-library-client</artifactId>
        <version>1.7.3</version>
      </dependency>

- **Download a release:**

  The [releases page](https://github.com/google/java-photoslibrary/releases)
  contains different artifacts for each library release, including jar files.
- **Clone the repository:**

  Use this method if you want to alter or contribute to this library, for
  example, submitting pull requests, or if you wish to try our samples. When you
  clone the repository, **all** files in this repository will be downloaded.
  1. Run `git clone https://github.com/google/java-photoslibrary.git` at the command prompt.
  2. You'll get a `java-photoslibrary` directory. Navigate to it by running `cd java-photoslibrary`.
  3. Open the `build.gradle` file in your IDE or run `./gradlew assemble` at the command prompt to build the project. See `./gradlew tasks` to see available tasks.

### Set up your OAuth2 credentials for Java

This client library works with the [Google Auth Library for
Java](https://github.com/google/google-auth-library-java). For more information,
refer to [Using OAuth 2.0 with the Google API Client Library for
Java](https://developers.google.com/api-client-library/java/google-api-java-client/oauth2).

Specify your client OAuth configuration in the `CredentialsProvider` when
creating the `PhotoLibrarySettings` for a `PhotosLibraryClient` object.

## Try out some samples

Try the code below to make your first API call using the Java client library.

    // Set up the Photos Library Client that interacts with the API
    PhotosLibrarySettings settings =
         PhotosLibrarySettings.newBuilder()
        .setCredentialsProvider(
            FixedCredentialsProvider.create(/* Add credentials here. */)) 
        .build();

    try (PhotosLibraryClient photosLibraryClient =
        PhotosLibraryClient.initialize(settings)) {

        // Create a new Album  with at title
        Album createdAlbum = photosLibraryClient.createAlbum("My Album");

        // Get some properties from the album, such as its ID and product URL
        String id = album.getId();
        String url = album.getProductUrl();

    } catch (ApiException e) {
        // Error during album creation
    }

There are more [samples](https://github.com/google/java-photoslibrary/tree/master/sample)
on GitHub for you to try.