@Override
    public String toString() {
        final ToStringHelper toStringHelper = MoreObjects.toStringHelper(this).omitNullValues();
        if (virtualHost != null) {
            toStringHelper.add("hostnamePattern", virtualHost.hostnamePattern());
        }
        if (!defaultHeaders.isEmpty()) {
            toStringHelper.add("defaultHeaders", defaultHeaders);
        }

        return toStringHelper.add("route", route)
                             .add("service", service)
                             .add("defaultServiceNaming", defaultServiceNaming)
                             .add("defaultLogName", defaultLogName)
                             .add("requestTimeoutMillis", requestTimeoutMillis)
                             .add("maxRequestLength", maxRequestLength)
                             .add("verboseResponses", verboseResponses)
                             .add("accessLogWriter", accessLogWriter)
                             .add("blockingTaskExecutor", blockingTaskExecutor)
                             .add("successFunction", successFunction)
                             .add("requestAutoAbortDelayMillis", requestAutoAbortDelayMillis)
                             .add("multipartUploadsLocation", multipartUploadsLocation)
                             .add("serviceErrorHandler", serviceErrorHandler)
                             .add("shutdownSupports", shutdownSupports)
                             .toString();
    }
Returns the default headers for an {@link HttpResponse} served by the {@link #service()}.
core/src/main/java/com/linecorp/armeria/server/ServiceConfig.java