App Engine 项目访问谷歌云存储的默认凭据？

Question

I have an app engine project, I want to access my google cloud storage default bucket. The first step of getting a Credential object fails, doing the following on a live instance:

Credential creds = GoogleCredential.getApplicationDefault();

The exception message I get:

"The Application Default Credentials are not available. They are available if running in Google Compute Engine. Otherwise, the environment variable GOOGLE_APPLICATION_CREDENTIALS must be defined pointing to a file defining the credentials. See https://developers.google.com/accounts/docs/application-default-credentials for more information."

The doc here says that production app engine projects should have access to the default credentials?:

https://developers.google.com/identity/protocols/application-default-credentials

"3. If you are running in Google App Engine production, the built-in service account associated with the application will be used."

Is there some setup I'm missing?

My app engine version (gradle):

com.google.appengine:appengine-java-sdk:1.9.18

and google cloud storage lib version:

com.google.apis:google-api-services-storage:v1-rev35-1.20.0

Thanks

Answer 1

Go to Google Developers Console -> Credentials and create a default service account .json key. When you do that, it will download a file like default-account-credentials.json for you. You must then put that file somewhere in your app engine project. This file will be referenced when you call

Credential creds = GoogleCredential.getApplicationDefault();

However, before that works you must set the environmental variable to that files location. To do that open up your appengine-web.xml file and put this line into it:

<env-variables>
            <env-var name="GOOGLE_APPLICATION_CREDENTIALS"
                value="WEB-INF/default-account-credentials.json" />
        </env-variables>

Where value is the path to your .json creds file you just downloaded.

Now it will work. (your gradle imports are fine)

Answer 2

I am posting this solution to help others like me who still need help with this error. Install gcloud on your system, select the project you want to use in the gcloud window, and then authenticate yourself using this command in the gcloud window: "gcloud auth application-default login" to generate a file called application_default_credentials.json. Your program running on the same system will then use this file automatically for authentication. Follow this link to install gcloud: https://cloud.google.com/docs/authentication/provide-credentials-adc?hl=en_GB