I am using google app engine and google datastore. I am using the google library
com.google.cloud.datastore.Datastore
My sample code is:
Datastore datastore = DatastoreOptions.getDefaultInstance().getService();
Key taskKey = datastore.newKeyFactory().setKind(entityName).newKey(id);
//populate some fields....
datastore.put(task);
I am using spring-boot and jetty as a container.
On local, it is working properly and the data updated in the google datastore.
The issue is when im deploying the app to the google-app-engine, im getting the Below exception when i get to datastore.put method.
com.google.cloud.datastore.DatastoreException: Request is missing required authentication credential. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.
com.google.cloud.datastore.spi.v1.HttpDatastoreRpc.translate(HttpDatastoreRpc.java:129)
com.google.cloud.datastore.spi.v1.HttpDatastoreRpc.commit(HttpDatastoreRpc.java:155)
com.google.cloud.datastore.DatastoreImpl$4.call(DatastoreImpl.java:485)
Note: in both, on local environment and google-app-engine, i defined the environment variable GOOGLE_APPLICATION_CREDENTIALS that point to json file with all required credentials generated by google API.
According to the documentation for connecting to Datastore from App Engine in Java, there are several options available, so you can either go with Objectify (third party library), Datastore API or Datastore Client Library.
With the usage of Client Libraries, you must know that they make use of the Application Default Credentials, in such a way that, as documented, if the environment variable GOOGLE_APPLICATION_CREDENTIALS, ADC uses the default service account that App Engine provides for applications running over that service. So in your case, I think you should not define the environment variable, so that App Engine uses its default Service Account.