为什么FetchType.EAGER在单元测试中不起作用？

Question

我的应用程序使用JPA（Hibernate）和Spring。我的恩赐是：

部门

@Entity
@Table(schema = "myschema")
public class Department {

    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "uuid2")
    @Column(columnDefinition = "BINARY(16)", length = 16 )
    private UUID uuid;

    @Column(name = "name", length = 200, nullable = false)
    private String name;

    @OneToMany(fetch = FetchType.EAGER, mappedBy = "department", cascade = CascadeType.ALL, orphanRemoval = true)
    List<User> users = new ArrayList<>();
}

用户

@Entity
@Table(schema = "myschema")
public class User {

    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "uuid2")
    @Column(columnDefinition = "BINARY(16)", length = 16 )
    private UUID uuid;

    @NotNull
    @Column(name = "login", length = 100, nullable = false)
    private String login;

    @ManyToOne
    @JoinColumn(name = "department_fk", nullable = false)
    private Department department;

}

DAO部门：

@Repository("departmentDao")
public class DepartmentDao {

    @PersistenceContext
    private EntityManager entityManager;

    @Transactional
    public UUID save(Department entity) {
        log.info("Department entity will be persisted", entity);
        entityManager.persist(entity);
        return entity.getUuid();
    }

    @Transactional
    public List<Department> getAllWithUsers() {
        log.info("Select all departments");
        CriteriaQuery<Department> criteria = entityManager.getCriteriaBuilder().createQuery(Department.class);
        Root<Department> root = criteria.from(Department.class);
        criteria.select(root);
        return entityManager.createQuery(criteria).getResultList();
    }
}

当我在Main类中运行代码时，它会加入实体：

主要

ApplicationContext context = new ClassPathXmlApplicationContext("META-INF/spring.xml");
UserDao userDao = (UserDao) context.getBean("userDao");
DepartmentDao departmentDao = (DepartmentDao) context.getBean("departmentDao");

Department newDep = new Department("WebDepartment", new Date());
departmentDao.save(newDep);

User newUser1 = new User("Test1", newDep);
User newUser2 = new User("Test2", newDep);
userDao.save(newUser1);
userDao.save(newUser2);

List<Department> deps = departmentDao.getAllWithUsers();

//deps
//[Department{name='WebDepartment', users = ['Test1', 'Test2']}]

当我使用相同的代码运行单元测试时，该部门有空的用户列表：

@ContextConfiguration(locations = "classpath:META-INF/spring-test.xml")
@RunWith(SpringJUnit4ClassRunner.class)
public class DaoTests {

    @Autowired
    private DepartmentDao departmentDao;

    @Autowired
    private UserDao userDao;

    @Test
    @Transactional
    public void daoTests() throws NoSuchAlgorithmException {

        Department newDep = new Department("WebDepartment", new Date());
        departmentDao.save(newDep);

        User newUser1 = new User("Test1", newDep);
        User newUser2 = new User("Test2", newDep);
        userDao.save(newUser1);
        userDao.save(newUser2);
        List<Department> deps = departmentDao.getAllWithUsers();

        //deps
        //[Department{name='WebDepartment', users = []}]
    }
}

所以，我的问题是：为什么EAGER在Main工作，但在测试中它没有？

Answer 1

我假设您没有将新用户添加到部门中的用户列表中。

您的构造函数必须如下所示：

public User(
            // other fields, 
            Department department) {
   // set all fields.

   department.getUsers().add(this);
}

在Main中它正在工作，因为你有两个事务，并且在读取时是在一个单独的事务中，而部门是从DB获取的。

但是在单元测试中，它从用户列表为空的内存中返回Department。

在保存实体之前保持关系正确非常重要。