application.yaml

##################################################################################
##################################################################################
######### IF YOU FOUND THIS GIST USEFUL, PLEASE LEAVE A STAR. THANKS. ############
##################################################################################
##################################################################################


spring:
  security:
    oauth2:
      resourceserver:
        jwt:
          issuer-uri: <ISSUER URI of the OIDC supported IAM Provider>
          
OR

spring:
  security:
    oauth2:
      resourceserver:
        jwt:
          jwk-set-uri: <JWK SET URI of the OIDC supported IAM Provider>

build.gradle

plugins {
	id 'org.springframework.boot' version '2.3.1.RELEASE'
	id 'io.spring.dependency-management' version '1.0.9.RELEASE'
	id 'java'
}

//Relevant dependencies

dependencies {
	implementation 'org.springframework.boot:spring-boot-starter-webflux'
	implementation 'org.springframework.boot:spring-boot-starter-oauth2-resource-server'
}

democontroller.java

@RestController
public class DemoController {

  @GetMapping(value = "/greet")
  public Mono<String> greet() {
    return Mono.just("Hello from Demo Project");
  }
}

Spring WebFlux Security- Resource Server config - OAuth2.0.md

To access the api in this example, first we have to procure the Auth Token (using one of the OAuth2 Flows) containing a scope "canGreet".

Assumption is that the Authorization Server supports OpenId Connect 1.0 specifications.

websecurityconfiguration.java

@EnableWebFluxSecurity
public class WebSecurityConfiguration {
  private static final String ACTUATOR_ENDPOINT_PATTERN = "/actuator/*";

  @Bean
  SecurityWebFilterChain springWebFilterChain(ServerHttpSecurity http) throws Exception {
    http
        .csrf().disable()
        .authorizeExchange()
        .pathMatchers(ACTUATOR_ENDPOINT_PATTERN)
        .permitAll()
        .pathMatchers("/greet")
        .hasAuthority("SCOPE_canGreet")
        .anyExchange().authenticated()
        .and()
        .oauth2ResourceServer()
        .jwt();

    return http.build();
  }
}