apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/api/AdminServiceAPI.java/NamespaceAPI/loadNamespace
class NamespaceAPI:    public NamespaceDTO loadNamespace(String appId, Env env, String clusterName,
        String namespaceName) {
      return
          restTemplate.get(env, "apps/{appId}/clusters/{clusterName}/namespaces/{namespaceName}",
              NamespaceDTO.class, appId, clusterName, namespaceName);
    }