apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/api/AdminServiceAPI.java/ClusterAPI/findClustersByApp
class ClusterAPI:    public List<ClusterDTO> findClustersByApp(String appId, Env env) {
      ClusterDTO[] clusterDTOs = restTemplate.get(env, "apps/{appId}/clusters", ClusterDTO[].class,
          appId);
      return Arrays.asList(clusterDTOs);
    }