apollo-portal/src/main/java/com/ctrip/framework/apollo/openapi/v1/controller/ClusterController.java/ClusterController/getCluster
class ClusterController:  @GetMapping(value = "apps/{appId}/clusters/{clusterName:.+}")
  public OpenClusterDTO getCluster(@PathVariable("appId") String appId, @PathVariable String env,
      @PathVariable("clusterName") String clusterName) {
    return this.clusterOpenApiService.getCluster(appId, env, clusterName);
  }