How do I connect to multiple databases/instances in GCP Spanner using Spring Cloud GCP Starter?

I am currently building an application that connects to a database on Spanner. The end goal of the application is to be able to connect to multiple databases (and possibly instances) so it can pull data using a GraphQL implementation. I am currently using Spring Cloud GCP Starter and Spring Cloud GCP Starter Data Spanner Maven packages to handle the configuration and data mapping. The Spring Cloud GCP Starter asks me to set up these lines in application.properties:

spring.cloud.gcp.spanner.instance-id=blah
spring.cloud.gcp.spanner.database=blah
spring.cloud.gcp.project-id=blah

Currently the application is set up to have models for each table, a repository (using SpannerRepository), and a controller.

The issue is I haven't been able to figure out how to change the configuration from the initial values when the application is run. Has anyone run into this and figured it out, or is it a limitation of my current implementation in Spring Cloud GCP Starter and I should look for different solution?

What I have tried:

• Tried finding someone with the same issue online, nothing similar that I can find currently
• Tried looking how to use/change the low level implementations things like SpannerTemplate that the autoconfiguration creates, but wasn't able to figure out how to change/use them
• Tried finding a way to change application.properties and reloading during runtime, but after some research this seemed like a horrible idea

Any help would be greatly appreciated, thank you!

I finally found it!

Documentation

By creating a custom bean for DatabaseIdProvider you can set the projectId, instanceId, and database to whatever you would like. Confirmed to be working the SpannerRepository implementation as well.

If anyone else finds this, here is an example of how you would create your own implementation (how you go about feeding it a new database name is up to you):

@Bean
public DatabaseIdProvider databaseIdProvider() {
    return () -> DatabaseId.of("projectId", "instanceId", "databaseName");
}

The DatabaseIdProvider interface extends Supplier<DatabaseId>. DatabaseId has a method (of) that creates the new DatabaseId that you need to connect to a different database/instance.