Hibernate Validator validation timing

Question

I've been googling a bit and I'm running out of time so I'm throwing this out here in the hopes that someone just knows the answer. I've got a system where I have spring transaction boundaries at the Service layer. Below that lies a dao layer. I've got bean validation on my model objects and I've wrapped the DAO's in a compile time aspectj Around aspect like this:

@Aspect
public class ValidationCollectorAspect {

  @Around("daoMethods()")
  public Object collectDaoMessages(ProceedingJoinPoint thisJoinPoint) throws Throwable {
    try {
      return thisJoinPoint.proceed();
    } catch (ConstraintViolationException e) {
      Set<ConstraintViolation<?>> constraintViolations = e.getConstraintViolations();
      List<UserMessage> userMessages = ThreadContext.MESSAGES.get();
      for (ConstraintViolation<?> constraintViolation : constraintViolations) {
        userMessages.add(new UserMessage(constraintViolation.getMessage(), MessageType.VALIDATION));
      }
      throw new MyPersistenceException("Validation failures", e);
    }
  }

  @Pointcut("call(public * *(..)) &&!call(* getEntityManager()) && within(com.myclient.dao.impl..*)")
  public void daoMethods() {
  }
}

The problem is the validation appears to happen when the transaction is committed, not prior to the save or update operation in the DAO. This means that the ConstraintViolationException from bean validation is not thrown until AFTER the service method returns and way after this join point. My evidence for this is that the stack trace does not contain any of the dao service methods. The first method for code I wrote is shown by

    at com.myclient.servlet.rest.Rest.updateObjects(Rest.java:323)

But that's a method on a servlet name Rest, and the whole point is to NOT need to create join points for a whole bunch of specific methods on the various servlets in the system, and also to be able to process the Constraint violation before it's wrapped in arbitrary layers of spring exceptions.

I understand that sometimes it might be cool to validate the sum total of all the hibernate changes, just before commit, but that's not what I want. (although as second round of validation it would not be unwelcome) How can I tell hibernate validator to process the validation when I call the hibernate save or update methods in the dao, not when the transaction commits?

Here's the versions of stuff from my build:

compile 'org.hibernate:hibernate-entitymanager:4.2.2.Final'
compile 'org.hibernate:hibernate-validator:5.0.1.Final'
compile 'org.hibernate:hibernate-c3p0:4.2.2.Final'
compile 'org.springframework:spring-orm:3.2.3.RELEASE'
compile 'org.springframework:spring-context:3.2.3.RELEASE'
compile 'org.springframework:spring-web:3.2.3.RELEASE'
compile 'javax.inject:javax.inject:1'
compile 'org.aspectj:aspectjrt:1.7.3'
ajc "org.aspectj:aspectjtools:1.7.3"

Edit: One further note... I'm doing all this under JPA, so I'd prefer a non-hibernate specific solution if one exists.

Answer 1

How can I tell hibernate validator to process the validation when I call the hibernate save or update methods in the dao, not when the transaction commits?

Implement a hibernate entity listeners and register the event listener for every event type when you want to do the validation.

Take a look at this question on how to configure event listeners with hibernate 4.

Answer 2

(Stack Overflow says this is too long to post as a comment, so posting it as an answer instead.)

I thought a bit about what you're trying to do, and can't figure out what the motivation is. So now I'm curious.

If you're receiving the object from some other piece of code and want it to be @Valid, you should be validating it before doing anything with it; not when calling save() or update(). You can either directly pass it to a validator or use the new method constraint support in Hibernate Validator 5 which will give you method validation using proxies.

If you're constructing the object yourself and are trying to catch code errors when you persist, that's a code smell. Why don't you have constructors or builders that prevent the construction of an invalid entity in the first place? And if you do have them but just want the double check when you persist, what difference would it make if the failures happen at save() time or at transaction commit, since the whole thing should roll back anyway?

You should also keep in mind that Hibernate does transactional write-behind and saves are deferred in the hope that they can be merged together to reduce chatter with the database. So if you want validation as a side-effect of saving, you should also expect that validation to be deferred or you're messing with semantics.

Anyway, I'd try HV5 method constraints at the DAO level and skip the custom validator as a first approach.

Answer 3

I'm not 100% sure I like this, but here's how I solved it. Basically I stopped trying to find a hibernate solution and added a couple of extra methods...

In my service layer:

  @Override
  public void save(T r) {
    // This allows us to post a join point just outside the transaction boundary
    save0(r);
  }

  @Transactional
  private void save0(T r) {
    getDao().save(r);
  }

  @Override
  public T update(T obj) throws IllegalArgumentException {
    // This allows us to post a join point just outside the transaction boundary
    return update0(obj);
  }

  @Transactional
  private T update0(T obj) {
    return getDao().update(obj);
  }

In my aspectJ pointcut

  @Around("daoMethods()")
  public Object collectDaoMessages(ProceedingJoinPoint thisJoinPoint) throws Throwable {
    try {
      return thisJoinPoint.proceed();
    } catch (Exception e) {
      ConstraintViolationException cve;
      Throwable cause = e;
      while (cause != null && !(cause instanceof ConstraintViolationException)) {
        cause = cause.getCause();
      }
      if (cause == null) {
        throw e;
      } else {
        cve = (ConstraintViolationException) cause;
      }

      Set<ConstraintViolation<?>> constraintViolations = cve.getConstraintViolations();
      List<UserMessage> userMessages = ThreadContext.MESSAGES.get();
      for (ConstraintViolation<?> constraintViolation : constraintViolations) {
        userMessages.add(new UserMessage(constraintViolation.getMessage(), MessageType.VALIDATION));
      }
      throw new MyPersistenceException("Validation failures", e);
    }
  }

  @Pointcut(
      "execution(public * *(..)) " +
      "&& !execution(public * load*(..)) " +
      "&& within(com.myclient.service.impl..*) "
  )
  public void daoMethods() {}