连接到Google App Engine数据存储区

Question

I am trying to connect to Google App Engine's Datastore from my local machine in Java. I will not be using the service with an application on GAE, it will be on AWS.

What I tried

I tried using DatastoreService datastore = DatastoreServiceFactory.getDatastoreService(); , but I think it is for when the application is hosted on GAE.

Right now, I have Google Storage up and running using a json credentials file fetched with the System Variable GOOGLE_APPLICATION_CREDENTIALS . The connection works fine, so my guess is that I might have to do something similar to Storage. I did something like this for Storage :

HttpTransport transport = GoogleNetHttpTransport.newTrustedTransport();
        JsonFactory jsonFactory = new JacksonFactory();
        GoogleCredential credential = GoogleCredential.getApplicationDefault(transport, jsonFactory);

        if (credential.createScopedRequired()) {
            Collection<String> bigqueryScopes = StorageScopes.all();
            credential = credential.createScoped(bigqueryScopes);
        }

        Storage client = new Storage.Builder(transport, jsonFactory, credential)
                .setApplicationName("APPLICATION_NAME")
                .build();

The question

So my question is : How can I connect to Google App Engine Datastore from outside of Google App Engine?

Thank you for your help!

Answer 1

I recommend that you move to the gcloud-java client library . It is built on top of the code that you are currently using, and makes it easier to work with the Datastore and Storage, although the documentation is virtually non-existent (as of April 2016).

This is how you connect to the Datastore using this library:

AuthCredentials credentials = AuthCredentials.createFor(account, key);
DatastoreOptions options = DatastoreOptions.builder()
        .authCredentials(credentials)
        .projectId(projectId)
        .namespace(NAMESPACE)
        .build();
Datastore datastore = options.service();

Same for the Storage, but with StorageOptions.

TIP: Open gcloud-java project in GitHub - the link is on the page that I referenced earlier. There is a folder which contains examples of how to use Datastore and Storage.

Answer 2

With Andrei Volgin's awesome help, I managed to be able to connect to Datastore from an application outside of Google App Engine. Here is what I did as of April 2016 :

• Enable Datastore API v1beta3. The default in App Engine for me was v1beta2. https://console.cloud.google.com/apis/api/datastore.googleapis.com/overview?project=PROJECT_NAME
• Get a credentials file for the service with Datastore activated.
• You can set the credentials file in a system variable with GOOGLE_APPLICATION_CREDENTIALS=/path/to/credentials.json

• I wrote this code as a test and the connection worked

   DatastoreOptions options = DatastoreOptions.builder() .projectId("PROJECT_NAME") .authCredentials(AuthCredentials.createForJson( new FileInputStream("/PATH/TO/CREDENTIALS.json"))).build(); Datastore datastore = options.service(); Query<Entity> query = Query.gqlQueryBuilder(Query.ResultType.ENTITY, "SELECT * FROM user").build(); QueryResults<Entity> results = datastore.run(query); while (results.hasNext()) { Entity result = results.next(); System.out.println(result.getString("id")); }