eureka | Run this project as a Spring Boot app ( e | Microservice library

Please note that Spring Cloud Gateway is not compatible with Spring MVC (spring-boot-starter-web). This is outlined in section "How to include Spring Cloud Gateway in the official reference documentation":

Spring Cloud Gateway is built on Spring Boot 2.x, Spring WebFlux, and Project Reactor. As a consequence, many of the familiar synchronous libraries (Spring Data and Spring Security, for example) and patterns you know may not apply when you use Spring Cloud Gateway.

Additionally, it is stated that:

Spring Cloud Gateway requires the Netty runtime provided by Spring Boot and Spring Webflux. It does not work in a traditional Servlet Container or when built as a WAR.

As already suggested by the error message, you would need to remove the dependency on spring-boot-starter-web. You can list all your direct and transitive dependencies with the following command:

There’s a relatively new Gradle feature called “version catalogs”. With those you can centrally declare dependencies that you’d like to share between multiple projects of your build (or even between different builds).

In your concrete example, you’d add something like the following to your settings.gradle file:

Your yaml is not valid. Check this validator as example.

Note how on line 16 and next, uri, predicates and path are not on the same column as just before.

Valid yaml is:

Is it possible to use Spring Authorization server without exposing it to outside?

The Spring Authorization Server is implementing the OAuth2 protocol. If we look at the specs, we can see that it's naturally a client, which wants to authenticate itself: https://datatracker.ietf.org/doc/html/rfc6749#section-1.2. In your setup, it seems like that client is not the gateway itself, but lets say an app. So if that app should use the Spring Authorization Server, it would authenticate with it (most of the time, that means acquiring a token), before the first interaction with the gateway happens. So to answer that question, if you want to use OAuth2 as it was meant to be used, you would need a direct connection between the app and the Spring Authorization Server, which means, it needs to be exposed to the outside. This makes perfect sense, since OAuth2 is meant to be used not with a single service, but with lots of different services, e.g. to allow single-sign-on.

What is the proper way to implement this?

You could setup your own Spring Authorization Server, implement your custom Authorization Code Grant logic, so that a client can authenticate itself and acquire a token. This could for example be a JSON Web Token (JWT). This can (should) be independent from your gateway and other services.

To authorize requests at the gateway, there are different ways. You could implement a logic yourself, which reads a JWT from the request and authorize it with the Spring Authorization Server or another identity provider, which you might have. You can also use Spring Cloud Security with the Spring Authorization Server, which is described here: https://spring.io/blog/2019/08/16/securing-services-with-spring-cloud-gateway. This is definitely a proper way to implement it.

One more thing: as you can see, OAuth2 comes with a price, being that it is not trivial to understand and configure. You must understand it in detail, before you deploy such a setup. On the other hand, its a solid standard and you can have feature like single-sign-on out of the box. So if you only need authorization for single or multiple apps to a single service, there are probably easier ways to gain a token and secure an app and OAuth2 is maybe overkill. But OAuth2 really pays off, if you have lots of services and lots of apps which should be authenticated with a central (sometimes company-wide) solution.

It seems like AWS Lambda Authorizers is something you're looking for: https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-use-lambda-authorizer.html These are lambda functions which can be used to authorize access to your APIs at the gateway level.

At Curity we have recently created such an authorizer which performs an introspection request to the Authorization Server to exchange an opaque token for a JWT: https://github.com/curityio/aws-phantom-token-lambda-authorizer It looks like you need something similar. Your authorizer could call the parent app, which will perform all the custom validations on the token and return a proper result, which then the AWS Lambda authorizer will use to make authorization decision.

According to the described setup, particularly:

You could build and publish your own container image if you wanted with a dockerfile like this

The fundamental problem here is that SelectableSectionType is a protocol that isn't restricted to class types and Reactive assumes that Base is a class (or otherwise is not going to be modified by the observable creation.)

I think the most generic you can make this is something like:

You just need req(), in a couple of places. Try this