149. Spring Cloud GCP Core

Each Spring Cloud GCP module uses GcpProjectIdProvider and CredentialsProvider to get the GCP project ID and access credentials.

Spring Cloud GCP provides a Spring Boot starter to auto-configure the core components.

Maven coordinates, using Spring Cloud GCP BOM:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-gcp-starter</artifactId>
</dependency>

Gradle coordinates:

dependencies {
    compile group: 'org.springframework.cloud', name: 'spring-cloud-gcp-starter'
}

149.1 Project ID

GcpProjectIdProvider is a functional interface that returns a GCP project ID string.

public interface GcpProjectIdProvider {
	String getProjectId();
}

The Spring Cloud GCP starter auto-configures a GcpProjectIdProvider. If a spring.cloud.gcp.project-id property is specified, the provided GcpProjectIdProvider returns that property value.

spring.cloud.gcp.project-id=my-gcp-project-id

Otherwise, the project ID is discovered based on an ordered list of rules:

  1. The project ID specified by the GOOGLE_CLOUD_PROJECT environment variable
  2. The Google App Engine project ID
  3. The project ID specified in the JSON credentials file pointed by the GOOGLE_APPLICATION_CREDENTIALS environment variable
  4. The Google Cloud SDK project ID
  5. The Google Compute Engine project ID, from the Google Compute Engine Metadata Server

149.2 Credentials

CredentialsProvider is a functional interface that returns the credentials to authenticate and authorize calls to Google Cloud Client Libraries.

public interface CredentialsProvider {
  Credentials getCredentials() throws IOException;
}

The Spring Cloud GCP starter auto-configures a CredentialsProvider. It uses the spring.cloud.gcp.credentials.location property to locate the OAuth2 private key of a Google service account. Keep in mind this property is a Spring Resource, so the credentials file can be obtained from a number of different locations such as the file system, classpath, URL, etc. The next example specifies the credentials location property in the file system.

spring.cloud.gcp.credentials.location=file:/usr/local/key.json

Alternatively, you can set the credentials by directly specifying the spring.cloud.gcp.credentials.encoded-key property. The value should be the base64-encoded account private key in JSON format.

If that credentials aren’t specified through properties, the starter tries to discover credentials from a number of places:

  1. Credentials file pointed to by the GOOGLE_APPLICATION_CREDENTIALS environment variable
  2. Credentials provided by the Google Cloud SDK gcloud auth application-default login command
  3. Google App Engine built-in credentials
  4. Google Cloud Shell built-in credentials
  5. Google Compute Engine built-in credentials

If your app is running on Google App Engine or Google Compute Engine, in most cases, you should omit the spring.cloud.gcp.credentials.location property and, instead, let the Spring Cloud GCP Starter get the correct credentials for those environments. On App Engine Standard, the App Identity service account credentials are used, on App Engine Flexible, the Flexible service account credential are used and on Google Compute Engine, the Compute Engine Default Service Account is used.

149.2.1 Scopes

By default, the credentials provided by the Spring Cloud GCP Starter contain scopes for every service supported by Spring Cloud GCP.

The Spring Cloud GCP starter allows you to configure a custom scope list for the provided credentials. To do that, specify a comma-delimited list of Google OAuth2 scopes in the spring.cloud.gcp.credentials.scopes property.

spring.cloud.gcp.credentials.scopes is a comma-delimited list of Google OAuth2 scopes for Google Cloud Platform services that the credentials returned by the provided CredentialsProvider support.

spring.cloud.gcp.credentials.scopes=https://www.googleapis.com/auth/pubsub,https://www.googleapis.com/auth/sqlservice.admin

You can also use DEFAULT_SCOPES placeholder as a scope to represent the starters default scopes, and append the additional scopes you need to add.

spring.cloud.gcp.credentials.scopes=DEFAULT_SCOPES,https://www.googleapis.com/auth/cloud-vision

149.3 Environment

GcpEnvironmentProvider is a functional interface, auto-configured by the Spring Cloud GCP starter, that returns a GcpEnvironment enum. The provider can help determine programmatically in which GCP environment (App Engine Flexible, App Engine Standard, Kubernetes Engine or Compute Engine) the application is deployed.

public interface GcpEnvironmentProvider {
	GcpEnvironment getCurrentEnvironment();
}

149.4 Spring Initializr

This starter is available from Spring Initializr through the GCP Support entry.