@Override
    public String handler(final String handle, final List<CommonUpstream> aliveList) {
        if ((StringUtils.isEmpty(handle) || EMPTY_LIST_JSON.equals(handle)) && CollectionUtils.isEmpty(aliveList)) {
            return EMPTY_LIST_JSON;
        }
        return GsonUtils.getInstance().toJson(doHandle(StringUtils.isEmpty(handle) ? EMPTY_LIST_JSON : handle, aliveList));
    }
Handler string.

@param handle the handle
@param aliveList the upstream live list
@return the string
shenyu-admin/src/main/java/org/apache/shenyu/admin/service/converter/AbstractSelectorHandleConverter.java