JPA Entity Validation

Question

Ok, I'm trying to setup an application in a Java EE Container. I use JPA for persistence and I also use the javax.validation.constraints.* constraints. By default the container validate the entities during the @PrePersist and @PreUpdate lifecycle events and it's good for me, but how do I handle the ConstraintViolationException?

I can't find any docs on it, any suggestion is welcomed.

Answer 1

Well, you could catch it :) Here is an example (from a unit test):

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

    @BeforeClass
    public static void createEntityManagerFactory() {
        emf = Persistence.createEntityManagerFactory("MyPu");
    }

    @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 nameTooShort() {
        try {
            Customer customer = new Customer("Bo");
            em.persist(customer);
            em.flush();
            fail("Expected ConstraintViolationException wasn't thrown.");
        } catch (ConstraintViolationException e) {
            assertEquals(1, e.getConstraintViolations().size());
            ConstraintViolation<?> violation = e.getConstraintViolations().iterator().next();

            assertEquals("name", violation.getPropertyPath().toString());
            assertEquals(Size.class, violation.getConstraintDescriptor().getAnnotation().annotationType());
        }
    }
}

Where my Customer looks like:

@Entity
public class Customer {
    @Id @GeneratedValue
    @NotNull
    private Long id;

    @NotNull
    @Size(min = 3, max = 80)
    private String name;

    private boolean archived;

    ...
}

But this was just an example to show a tiny part of the API.

In my opinion, you should actually handle the validation at the view level. Many presentation frameworks support Bean Validation: JSF 2.0, Wicket, Spring MVC...

See also

• 6.3. Presentation layer validation
• Spring MVC, Spring Bean Validation Framework and validating confirm password / confirm email fields.
• Wicket JSR-303 Validators
• TOTD #123: f:ajax, Bean Validation for JSF, CDI for JSF and JPA 2.0 Criteria API

Answer 2

You can catch ConstraintViolationException, as Pascal described it, but please be aware, that this Exception could be thrown anytime after your create/update statement, and before the end of the transaction (see FlushModeType). Typical throwing points are when you read something after your create/update statement, or at an explicit flush() statement (which you should use with caution).