[JavaForFun] /

package de.spring.webservices.rest.controller.adapters;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.context.request.async.DeferredResult;

import rx.Observable;
import rx.schedulers.Schedulers;

public class RxJavaAdapter {
        private static final Logger LOGGER = LoggerFactory.getLogger(RxJavaAdapter.class);
        
        // With no value, we depend on the Tomcat/Jboss/Jetty/etc timeout value for asynchronous requests.
        // Spring will answer after 60 secs with an empty response (by default) and HTTP 503 status (by default) when timeout.
        private static final long ASYNC_TIMEOUT = 60000;  /* milliseconds */

        
        @FunctionalInterface
        public interface DeferredCall<T> {
                
                public T doCall();
        }
        
        public static final <T> DeferredResult<T> deferredAdapter(Observable<T> observable) {

        DeferredResult<T> deferredResult = new DeferredResult<>(ASYNC_TIMEOUT);

        observable
                .subscribeOn(Schedulers.io())
                .subscribe(deferredResult::setResult, exception -> {
                        Throwable realException = launderException(exception);

                        LOGGER.error("error: ", realException);

                        deferredResult.setErrorResult(realException);
                        });

        return deferredResult;  
        }
        
        private static final Throwable launderException(Throwable exception) {
                return exception.getCause() != null
                           ? exception.getCause()
                           : exception;
        }
}