Asynchronous REST client

Question

How to write asynchronous REST client?

My controller (not sure if it's enough for being async):

@RequestMapping(method = RequestMethod.GET, value = "/get/all")
@ResponseBody
public Callable < CustomersListDTO > getAllCustomers() {
    return new Callable < CustomersListDTO > () {

        @Override
        public CustomersListDTO call() throws Exception {
            Thread.sleep(2000);
            return customerService.getAllCustomers();
        }

    };
}

My synchronous REST client method:

public Response get_all_customers() {
    ResponseEntity < CustomersListDTO > response;
    try {
        response = restTemplate.getForEntity(
            getMethodURI(ServiceExplanation.GET_ALL_CUSTOMERS),
            CustomersListDTO.class
        );
        message = "Customers obtained successfully!";
    } catch (HttpServerErrorException ex) {
        message = "ERROR: " + ex.getMessage() + " - " + ex.getResponseBodyAsString();
    } catch (HttpClientErrorException ex) {
        message = "ERROR: " + ex.getMessage() + " - " + ex.getResponseBodyAsString();
    } catch (RestClientException ex) {
        message = checkIfServerOrInternetDown();
    }

    return formResponse(message, response);
}

How do I make it asynchronous? How can the CLIENT continue doing other tasks while SERVER is obtaining data and later return found data?

Answer 1

If you are looking for REST asynchronous client implementation, you can take a look at Jersey's asynchronous client API. It can be easily integrated with Spring.