Unable to access the cause in FallbackFactory

I have the HystrixFeign client and I am trying to get the cause/exception in my fallback implementation, because I would really like to know the reason for fallback so I can fix the issue why the service call has failed. But the below implementations are not getting me the cause. This works just fine and the fallback is getting called all the time. But I have no clue why. I am new to Feign and Hystrix. My application is written in java 1.6 years back and this is kind of enhancement call. So I cant go for any lambda expressions.

I have the client interface defined like below

public interface MyServiceFeignClient {

    @RequestLine("POST /myService/order")
    @Headers("Content-Type:application/vnd.org.company.domain.order+json;version=1.0")
    ServiceResponse sendOrder(String content);

}

My FeignClientFacory is like below

public class FeignClientFactory {

    private static final Logger LOG = LoggerFactory.getLogger(FeignClientFactory.class);
    private String serviceUrl;

    public FeignClientFactory(final String serviceUrl) {
        this.serviceUrl = serviceUrl;
    }

    public MyServiceFeignClient newInstance() {
        return HystrixFeign.builder()
            .decoder(new GsonDecoder())
            .target(MyServiceFeignClient.class, serviceUrl, new ClientFallbackFactory());
    }

    static class ClientFallbackFactory implements MyServiceFeignClient, FallbackFactory<ClientFallbackFactory> {

        final Throwable cause;

        public ClientFallbackFactory() {
            this(null);
        }

        ClientFallbackFactory(Throwable cause) {
            this.cause = cause;
        }

        // note that this method is not getting called at all
        @Override
        public ClientFallbackFactory create(Throwable cause) {
            if (cause != null) {
                String errMessage = StringUtils.isNotBlank(cause.getMessage()) ? cause.getMessage() : "unknown error occured";
                // I don't see this log statement
                LOG.debug("Client fallback called for the cause : {}", errMessage);
            }
            return new ClientFallbackFactory(cause);
        }

        // everytime this method is called as fallback and the cause is just NULL
        @Override
        public ServiceResponse sendOrder(String content) {
            LOG.debug("service client api fallback called");
            ServiceResponse response = new ServiceResponse();
            String errMessage = (cause == null ? "service client api fallback called" : cause.getMessage());
            response.setErrorMessage(errMessage);
            response.setResultStatus("WARN");
            return response;
        }
    }
}

My test case is like below.

    @Test
    public void testSendOrderToPaymentRiskService() {

        String order = loadFile("/order.json");
        ServiceResponse response = client.sendOrder(order);
        // status is always WARN - so fallback is getting called everytime.
        assertThat(response.getResultStatus()).isEqualTo("SUCCESS");
        assertThat(response.getTransactionId()).isNotNull();
        // getting the error message "service client api fallback called"
        assertThat(response.getErrorMessage).isNull();

    }

[seetharamani]

So taking the test case and start modifying it one by one helped me fix the issue. FallbackFactory is getting me the cause. Thank you @adriancole and @spencergibb

[spencergibb]

You’ll need to cast it as a FallbackFactory to select the appropriate method since your class is both.