Hibernate @OneToOne @NotNull

Question

在关系的两边声明@OneToOne和@NotNull是否有效，例如：

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;
     }
 }

我找不到任何东西说这是无效的，但似乎在坚持期间，至少有一方的关系必须被违反。(例如，如果首先写入changeEntry，则changeEntryDetails暂时为空)。

在尝试此操作时，我看到一个异常抛出not-null property references a null or transient value。

如果可能的话，我想避免放松约束，因为双方都必须在场。

Answer 1

在关系的两边声明@OneToOne和@NotNull是否有效(.)我找不到任何东西说这是无效的，但似乎在坚持期间，至少有一方的关系必须被违反。(例如，如果首先写入changeEntry，则changeEntryDetails暂时为空)。

它是有效的，每件事都能很好地处理映射好的实体。您需要将双向关联的一方声明为“拥有”方(此“控件”为插入顺序)。一个可能的工作解决办法是：

@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(请注意在关联的非拥有方设置的mappedBy属性)：

@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，下列测试(为演示目的)通过：

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());
    }
}

Answer 2

因为您的级联类型，所以它应该持久化瞬态值。

如果在设置另一个瞬态元素之前，您实际上正在尝试持久化第一个元素，那么您将预期会出现此错误。

您指定的约束仅指定数据库中的值不能为空，而不是在数据模型中，显然，当您构造对象的新实例时，引用将为空。当引用为null时，不能持久化该实体。

Answer 3

如果您在这里遇到了与 openJPA 和Pascals解决方案相同的问题，那么您可能需要在persistence.xml中将openJPA属性openjpa.InverseManager设置为true。