apollo-openapi/src/main/java/com/ctrip/framework/apollo/openapi/client/service/ItemOpenApiService.java/ItemOpenApiService/removeItem
class ItemOpenApiService:  @Override
  public void removeItem(String appId, String env, String clusterName, String namespaceName, String key, String operator) {
    if (Strings.isNullOrEmpty(clusterName)) {
      clusterName = ConfigConsts.CLUSTER_NAME_DEFAULT;
    }
    if (Strings.isNullOrEmpty(namespaceName)) {
      namespaceName = ConfigConsts.NAMESPACE_APPLICATION;
    }

    checkNotEmpty(appId, "App id");
    checkNotEmpty(env, "Env");
    checkNotEmpty(key, "Item key");
    checkNotEmpty(operator, "Operator");

    OpenApiPathBuilder pathBuilder = OpenApiPathBuilder.newBuilder()
        .envsPathVal(env)
        .appsPathVal(appId)
        .clustersPathVal(clusterName)
        .namespacesPathVal(namespaceName)
        .itemsPathVal(key)
        .addParam("operator", operator);

    try (CloseableHttpResponse ignored = delete(pathBuilder)) {
    } catch (Throwable ex) {
      throw new RuntimeException(String
          .format("Remove item: %s for appId: %s, cluster: %s, namespace: %s in env: %s failed", key, appId,
              clusterName, namespaceName, env), ex);
    }

  }