public class CorrelationHandler implements HttpHandler {

    private static final HttpString HEADER = new HttpString("X-CORR-ID");

    private final HttpHandler next;

    public CorrelationHandler(HttpHandler next) {
        this.next = next;
    }

    @Override
    public void handleRequest(HttpServerExchange exchange) throws Exception {
        String corr = exchange.getRequestHeaders().getFirst(HEADER);
        if(corr != null) {
            exchange.getResponseHeaders().put(HEADER, corr);
        }
        next.handleRequest(exchange);

    }
}