java – springboot graphql instrospection 405 method not allowed error

I am deploying both react and springboot to digitalocean app platform. I am using springboot graphql, and i want to do schema instrospection.

To deploy both frontend and backend, i need to add a route value “api/” to the original backend url, i.e. APP_URL = ${APP_URL}/api.

for example:
before changing the url , my graphiql url is original.digitalocean.app/graphiql?path=graphql;
after changing the url, my graphiql url is original.digitalocean.app/api/graphiql?path=graphql;

I am able to introspect the graphql schema with : original.digitalocean.app/graphiql?path=graphql.

but i get “405 method not allowed” error with : original.digitalocean.app/api/graphiql?path=graphql.

Thanks in advance for any help!