休眠@OneToOne @NotNull [英] Hibernate @OneToOne @NotNull

问题描述

在关系的两边声明@OneToOne和@NotNull是否有效，例如:

Is it valid to declare @OneToOne and @NotNull on both sides of a relationship, such as:

class ChangeEntry
{
    @OneToOne(cascade=CascadeType.ALL)
    @NotNull
    ChangeEntryDetails changeEntryDetails;

    public void addDetails(ChangeEntryDetails details) {
       this.changeEntryDetails = details;
       details.setChangeEntry(this);
    }
 }

 class ChangeEntryDetails
 {
     @OneToOne(cascase=CascadeType.ALL)
     @NotNull
     ChangeEntry changeEntry;

     public void setChangeEntry(ChangeEntry changeEntry)
     {
          this.changeEntry = changeEntry;
     }
 }

我找不到任何说这是无效的，但似乎在持久性期间，至少必须违反关系的一侧.(比如先写changeEntry，changeEntryDetails会暂时为空)

I can't find anything that says this is invalid, but it seems that during persistence at least one side of the relationship must be violated. (Eg., if writing changeEntry first, changeEntryDetails will be null temporarily).

尝试此操作时，我看到抛出异常not-null 属性引用空值或瞬态值.

When trying this, I see an exception thrown not-null property references a null or transient value.

如果可能，我想避免放松约束，因为双方必须都在场.

I'd like to avoid relaxing the constraint if possible, because both sides must be present.

推荐答案

在关系的双方声明 @OneToOne 和 @NotNull 是否有效 (...) 我找不到任何说明这是无效的，但似乎在坚持期间，至少必须违反关系的一侧.(比如先写changeEntry，changeEntryDetails会暂时为null).

Is it valid to declare @OneToOne and @NotNull on both sides of a relationship (...) I can't find anything that says this is invalid, but it seems that during persistence at least one side of the relationship must be violated. (e.g. if writing changeEntry first, changeEntryDetails will be null temporarily).

它是有效的，并且在正确映射实体的情况下一切正常.您需要将双向关联的一侧声明为拥有"侧(此控制"插入顺序).一种可能的工作解决方案:

It is valid and everything works fine with properly mapped entities. You need to declare one side of your bi-directional association as the "owning" side (this "control" the order of inserts). One possible working solution:

@Entity
@NamedQueries( { @NamedQuery(name = ChangeEntry.FIND_ALL_CHANGEENTRIES, query = "SELECT c FROM ChangeEntry c") })
public class ChangeEntry implements Serializable {
    public final static String FIND_ALL_CHANGEENTRIES = "findAllChangeEntries";

    @Id
    @GeneratedValue
    private Long id;

    @OneToOne(optional = false, cascade = CascadeType.ALL)
    @JoinColumn(name = "DETAILS_ID", unique = true, nullable = false)
    @NotNull
    private ChangeEntryDetails changeEntryDetails;

    public void addDetails(ChangeEntryDetails details) {
        this.changeEntryDetails = details;
        details.setChangeEntry(this);
    }

    // constructor, getters and setters
}

对于另一个实体(注意 mappedBy 属性设置在关联的非拥有方):

And for the other entity (note the mappedBy attribute set on the non-owning side of the association):

@Entity
public class ChangeEntryDetails implements Serializable {
    @Id
    @GeneratedValue
    private Long id;

    @OneToOne(optional = false, mappedBy = "changeEntryDetails")
    @NotNull
    private ChangeEntry changeEntry;

    // constructor, getters and setters
}

对于这些实体，以下测试(用于演示目的)通过:

With these entities, the following test (for demonstration purposes) passes:

public class ChangeEntryTest {
    private static EntityManagerFactory emf;    
    private EntityManager em;

    @BeforeClass
    public static void createEntityManagerFactory() {
        emf = Persistence.createEntityManagerFactory("TestPu");
    }    
    @AfterClass
    public static void closeEntityManagerFactory() {
        emf.close();
    }    
    @Before
    public void beginTransaction() {
        em = emf.createEntityManager();
        em.getTransaction().begin();
    }    
    @After
    public void rollbackTransaction() {   
        if (em.getTransaction().isActive()) {
            em.getTransaction().rollback();
        }
        if (em.isOpen()) {
            em.close();
        }
    }

    @Test 
    public void testCreateEntryWithoutDetails() {
        try {
            ChangeEntry entry = new ChangeEntry();
            em.persist(entry);
            fail("Expected ConstraintViolationException wasn't thrown.");
        } catch (ConstraintViolationException e) {
            assertEquals(1, e.getConstraintViolations().size());
            ConstraintViolation<?> violation = e.getConstraintViolations()
                .iterator().next();

            assertEquals("changeEntryDetails", violation.getPropertyPath()
                .toString());
            assertEquals(NotNull.class, violation.getConstraintDescriptor()
                .getAnnotation().annotationType());
        }
    }

    @Test
    public void testCreateDetailsWithoutEntry() {    
        try {
            ChangeEntryDetails details = new ChangeEntryDetails();
            em.persist(details);
            fail("Expected ConstraintViolationException wasn't thrown.");
        } catch (ConstraintViolationException e) {
            assertEquals(1, e.getConstraintViolations().size());
            ConstraintViolation<?> violation = e.getConstraintViolations()
                .iterator().next();

            assertEquals("changeEntry", violation.getPropertyPath()
                .toString());
            assertEquals(NotNull.class, violation.getConstraintDescriptor()
                .getAnnotation().annotationType());
        }
    }

    @Test
    public void validEntryWithDetails() {
        ChangeEntry entry = new ChangeEntry();
        ChangeEntryDetails details = new ChangeEntryDetails();
        entry.addDetails(details);
        em.persist(entry);

        Query query = em.createNamedQuery(ChangeEntry.FIND_ALL_CHANGEENTRIES);
        assertEquals(1, query.getResultList().size());
    }
}

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