How I Decoupled Circuit Breaker from the Code with AOP in Spring Boot for Better Code Maintenance

DownstreamServiceSample.java

//code is omitted for brevity

@Service
public class DownstreamService {
  private final CircuitBreaker circuitBreaker;

  /**
   * Instantiates a new Res 4 j service.
   */
  public DownstreamService(CircuitBreakerRegistry circuitBreakerRegistry) {
    this.circuitBreaker = circuitBreakerRegistry.circuitBreaker("myAPOConfiguredMyCircuitBreaker");
  }
  
  //code is omitted for brevity
  
  public JSONObject callTestSlow() {

    Supplier<Object> supplier = () -> {
      JSONObject result;

      try
      {

        String serviceUrl = "http://localhost:3000/testslow";
        RestTemplate restTemplate = new RestTemplate();
        result = restTemplate.getForObject(serviceUrl, JSONObject.class);

      } catch (HttpClientErrorException ex)
      {
        throw new RuntimeException("external API error");
      } catch (Exception ex)
      {
        throw new RuntimeException("server error");
      }

      JSONObject payloadJSONObject = new JSONObject();
      payloadJSONObject.putAll(result);
      return payloadJSONObject;
    };

    return (JSONObject) this.execute(supplier, this::fallback);
  }

  private <T> T execute(Supplier<T> supplier, Function<Throwable, T> fallback) {
    return Decorators.ofSupplier(supplier)
            .withCircuitBreaker(circuitBreaker)
            .withFallback(fallback)
            .get();
  }

  private ResponseEntity<String> fallback(Throwable ex) {
    throw new CircuitBreakerDownstreamCallException(ex.getMessage());
  }
  
  //code is omitted for brevity
  
}