apollo-adminservice/src/main/java/com/ctrip/framework/apollo/adminservice/controller/NamespaceController.java/NamespaceController/get
class NamespaceController:  @GetMapping("/apps/{appId}/clusters/{clusterName}/namespaces/{namespaceName:.+}")
  public NamespaceDTO get(@PathVariable("appId") String appId,
                          @PathVariable("clusterName") String clusterName,
                          @PathVariable("namespaceName") String namespaceName) {
    Namespace namespace = namespaceService.findOne(appId, clusterName, namespaceName);
    if (namespace == null) {
      throw new NotFoundException("namespace not found for %s %s %s", appId, clusterName,
          namespaceName);
    }
    return BeanUtils.transform(NamespaceDTO.class, namespace);
  }