protected String getClassname(JsonObject obj, String prefix) {
        String clazzName = System.getProperty(prefix);
        // TODO Something of a hack because the constants may assume apiman-gateway prefix, which isn't in the vert.x JSON.
        String strippedPrefix = StringUtils.substringAfter(prefix, "apiman-gateway.");
        String filteredPrefix = strippedPrefix.isEmpty() ? prefix : strippedPrefix;

        if (clazzName == null) {
            Map<String, String> mfp = toFlatStringMap(obj);
            return mfp.get(filteredPrefix + "." + GATEWAY_CLASS);
        }

        return clazzName;
    }
@see io.apiman.gateway.engine.IEngineConfig#getGatewayInitializers(io.apiman.gateway.engine.IPluginRegistry)
gateway/platforms/vertx3/vertx3/src/main/java/io/apiman/gateway/platforms/vertx3/common/config/VertxEngineConfig.java