java - 空指针异常取决于 Mockito 中的语句链接？

Question

我有一个测试方法，应该测试以下方法:

public class SelectionVariantUniqueConstraintValidatorImpl implements UniqueConstraintValidator {

    private SessionFactory sessionFactory;

    @Override
    public List<Criteria> buildValidationCriteria(Object entity, Serializable id, String[] propertyNames) {
        final SelectionVariant selectionVariant = (SelectionVariant) entity;
        final Session session = sessionFactory.getCurrentSession();
        final Criteria criteria = session.createCriteria(SelectionVariant.class);

        criteria.add(Restrictions.eq("client", selectionVariant.getClient()));
        criteria.add(Restrictions.eq("variant.variantName", selectionVariant.getVariant().getVariantName()));

        return new ArrayList<Criteria>(Arrays.asList(criteria));
    }

    @Required
    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }
}

运行良好。但如果我修改这些行如下:

final Criteria criteria = session.createCriteria(SelectionVariant.class).add(Restrictions.eq("client", selectionVariant.getClient()));
criteria.add(Restrictions.eq("variant.variantName", selectionVariant.getVariant().getVariantName()));

我会得到:

java.lang.NullPointerException
    at com.innflow.ebtam.dao.hibernate.variant.SelectionVariantUniqueConstraintValidatorImpl.buildValidationCriteria(SelectionVariantUniqueConstraintValidatorImpl.java:35)

为什么？我缺少什么？

这是我的测试类:

@RunWith(MockitoJUnitRunner.class)
public class SelectionVariantUniqueConstraintValidatorImplTest {

    SelectionVariantUniqueConstraintValidatorImpl selectionVariantUniqueConstraintValidator
            = new SelectionVariantUniqueConstraintValidatorImpl();

    @Mock
    private SessionFactory sessionFactory;
    @Mock
    private Session session;
    @Mock
    private Criteria criteria;

    @Before
    public void setUp() throws Exception {
        selectionVariantUniqueConstraintValidator.setSessionFactory(sessionFactory);
    }

    @Test
    public void testBuildValidationCriteria() throws Exception {
        Mockito.when(sessionFactory.getCurrentSession()).thenReturn(session);
        Mockito.when(session.createCriteria(SelectionVariant.class)).thenReturn(criteria);
        SelectionVariant selectionVariant = new SelectionVariant();
        Client client = new ClientBuilder().businessKey("HPD").description("desc").version(0).id(1L).build();
        selectionVariant.setClient(client);
        selectionVariantUniqueConstraintValidator.buildValidationCriteria(selectionVariant, null, null);
        Mockito.verify(criteria,Mockito.atLeastOnce()).add(Restrictions.eq("client", Mockito.any(Client.class)));
    }
}

Answer 1

您必须模拟Criteria 的add 方法。这就是这里发生的事情。在您的第一个版本中，您模拟了标准实例。当您调用方法 add() 时，它不会执行任何操作并返回 null 但它不会打扰您，因为您不使用返回值。

但是，您在第二个版本中确实使用了 add() 的返回值。为了使其正常工作，您应该:

1. 使mockito调用真实的add()方法\
2. 模拟 add() 方法以使其返回原始条件

例如:

when(criteria.add(any(Restrictions.class))).thenCallRealMethod();

或

when(criteria.add(any(Restrictions.class))).thenReturn(criteria)

(我不确定它应该是Restrictions.class:它应该是Restrictions.eq()的类)