Async Spring Rest Controller - Process future result - spring

Question

I am new to futures and I am trying to figure out how I can process the Listenable future in this senario:
#Controller
#EnableAutoConfiguration
public class ListenableFutureAsyncController {
#Autowired
IHeavyLiftingService heavyLiftingService;
#RequestMapping("/")
#ResponseBody
DeferredResult<String> home() {
// Create DeferredResult
final DeferredResult<String> result = new DeferredResult<>();
//Call to the async service
ListenableFuture<ResponseEntity<String>> future = heavyLiftingService.heavyLifting();
future.addCallback(
new ListenableFutureCallback<ResponseEntity<String>>() {
#Override
public void onSuccess(ResponseEntity<String> response) {
result.setResult(response.getBody());
}
#Override
public void onFailure(Throwable t) {
result.setErrorResult(t.getMessage());
}
});
// Return the thread to servlet container,
// the response will be processed by another thread.
return result;
}
}
How can I process the future here other than passing it back to the controller. Ex. What if I want to save the future string to the db?
#Service
public class HeavyLiftingServiceImpl implements IHeavyLiftingService {
public ListenableFuture<String> heavyLifting() {
AsyncRestTemplate asycTemp = new AsyncRestTemplate();
ListenableFuture<String> future = asycTemp.execute(url, method, requestCallback, responseExtractor, urlVariable);
/**
/Save future string to db
**/
return future;
}
}

Answer 1

I have found a way to do this using Spring's ListenableFutureAdapter
#Service
public class HeavyLiftingServiceImpl implements IHeavyLiftingService {
public ListenableFuture<String> heavyLifting() {
AsyncRestTemplate asycTemp = new AsyncRestTemplate();
ListenableFuture<String> future = asycTemp.execute(url, method, requestCallback, responseExtractor, urlVariable);
ListenableFutureAdapter<String, String> chainedFuture;
chainedFuture = new ListenableFutureAdapter<String, String>(future) {
#Override
protected String adapt(String adapteeResult)
throws ExecutionException {
String parsedString = parse(adapteeResult);
return adapteeResult;
}
};
return chainedFuture;
}
}
I would recommend using Guava's implementation of listenable future. I find it more readable and documentation on chaining them together is easier to find.