微服务系列zuul（一）

    /**
     * to classify a filter by type. Standard types in Zuul are "pre" for pre-routing filtering,
     * "route" for routing to an origin, "post" for post-routing filters, "error" for error handling.
     * We also support a "static" type for static responses see  StaticResponseFilter.
     * Any filterType made be created or added and run by calling FilterProcessor.runFilters(type)
     *
     * @return A String representing that type
     */
    abstract public String filterType();

    /**
     * filterOrder() must also be defined for a filter. Filters may have the same  filterOrder if precedence is not
     * important for a filter. filterOrders do not need to be sequential.
     *
     * @return the int order of a filter
     */
    abstract public int filterOrder();