WebSecurityConfigurationPart1.java

@Configuration
public class WebSecurityConfiguration extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.authorizeRequests()
                .anyRequest()
                .authenticated();

        http.oauth2ResourceServer()
                .jwt();
    }
}

Just in case someone is coming from the article in Spring Security 6.1.x it will look like:

@RequiredArgsConstructor
@Configuration
public class WebSecurityConfiguration  {

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http, AuthenticationConfiguration authenticationConfiguration) throws Exception {
        http.authorizeHttpRequests(auth -> auth.anyRequest().authenticated()).oauth2ResourceServer((oauth2) -> oauth2.jwt(Customizer.withDefaults()));

        return http.build();
    }
}