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如何在Java中检查null的Long值？

这会有用吗？

if ( longValue == null) { return blah; }

我正在处理一个 graphql 问题，在该问题中我收到请求的以下错误

{
  customer(id: "5ed6092b-6924-4d31-92d0-b77d4d777b47") {
    id
    firstName
    lastName
    carsInterested
  }
}

 "message": "Validation error of type SubSelectionRequired: Sub selection required for type null of field carsInterested @ 'customer/carsInterested'",

下面是我的架构

type Customer {
  id: ID!
  firstName: String!
  lastName: String!
  # list of cars that the customer is interested in
  carsInterested: [Car!]

}

type Query {
  # return 'Customer'
  customer(id: ID!): Customer
}

我确实有一个 CustomerResolver，里面有函数 carsInterested。它看起来如下

@Component
public class CustomerResolver implements GraphQLResolver<Customer> {

    private final CarRepository carRepo;

    public CustomerResolver(CarRepository carRepo) …

java.lang.NoClassDefFoundError我在部署代码时感到很奇怪。编译时没有错误，但是当我使用 jetty 部署它时，出现错误

org.springframework.beans.factory.BeanCreationException:
 Error creating bean with name 'org.springframework.dao.annotation.
                                  PersistenceExceptionTranslationPostProcessor#0'
 defined in class path resource [applicationContext-dao.xml]:
  Initialization of bean failed;

nested exception is 
 org.springframework.beans.factory.BeanCreationException:
  Error creating bean with name 'sessionFactory'
  defined in class path resource [applicationContext-dao.xml]:
   Invocation of init method failed;

nested exception is
 java.lang.NoClassDefFoundError: com/core/model/Webhook$Event

该类如下所示

public class Webhook extends BaseObject implements Serializable {

    public enum Event {
        ORDER_CREATE,
        ORDER_UPDATE,
        ORDER_DELETE,
        TICKET_CREATE,
        TICKET_UPDATE,
        TICKET_DELETE,
        CUSTOMER_CREATE,
        CUSTOMER_UPDATE,
        CUSTOMER_DELETE,
        MENU_ITEM_UPDATE,
        CHECK_OFFER
    }

    private Event triggerEvent;

    public Event getTriggerEvent() { …