Money Java Async API

JMoney.java

public class JMoney {
    public static <T, S extends CompletionStage<T>, E extends Exception> S traceAsync(String spanName, CheckedCallable<S, E> callable) throws E {

        Tracer tracer = tracer();
        tracer.startSpan(spanName);

        S stage;
        try {
            stage = callable.call();
        } catch (Exception exception) {
            tracer.stopSpan(false);
            @SuppressWarnings("unchecked")
            E checked = (E) exception;
            throw checked;
        }

        if (stage != null) {
            CompletableFuture<T> future = stage.toCompletableFuture();
            if (future.isDone()) {
                boolean success = !(future.isCompletedExceptionally() || future.isCancelled());
                tracer.stopSpan(success);
            } else {
                Option<Span> span = SpanLocal.pop();
                if (span.isDefined()) {
                    Map<String, String> mdc = MDC.getCopyOfContextMap();
                    stage.whenComplete((result, exception) -> {
                        Map<String, String> previous = MDC.getCopyOfContextMap();
                        if (mdc != null) {
                            MDC.setContextMap(mdc);
                        } else {
                            MDC.clear();
                        }
                        
                        SpanLocal.push(span.get());
                        boolean success = exception == null;
                        tracer.stopSpan(success);
                        
                        if (previous != null) {
                            MDC.setContextMap(previous);
                        } else {
                            MDC.clear();
                        }
                    });
                }
            }
        } else {
            tracer.stopSpan(true);
        }

        return stage;
    }
}