JPA: OptimisticLockException and Cascading

Question

In my current project I use Spring Data JPA with Hibernate but consider this as a more general question that should also cover \"plain\" JPA.

I\'m uncertain how I should

Answer 1

What was bothering me is that the exceptions provided by JPA (Hibernate) and Spring do not actually return the current version of the failed object. So if a User needs to decide what to do, he obviously needs to see the updated, most current version. Just retarded an error to his call seems retarded to me. I mean you are already at database level in a transaction so getting the new current value directly has no cost...

I created a new Exception that holds a reference to the newest version of the entity that failed to update:

public class EntityVersionConflictException {

    @Getter
    private final Object currentVersion;

    public EntityVersionConflictException(
            ObjectOptimisticLockingFailureException lockEx,
            Object currentVersion){
        super(lockEx);
        this.currentVersion = currentVersion;
    }

    public Object getConflictingVersion() {
        return ((OptimisticLockException)getCause().getCause()).getEntity();
    }

    public Class getEntityClass() {
        return getCause().getPersistentClass();
    }

    @Override
    public ObjectOptimisticLockingFailureException getCause(){
        return (ObjectOptimisticLockingFailureException)super.getCause();
    }
}

and the according Service method

try {
    return getRepository().save(entity);
} catch (ObjectOptimisticLockingFailureException lockEx) {
    // should only happen when updating existing entity (eg. merging)
    // and because entites do not use CascadeType.MERGE
    // the entity causing the issue will always be the of class
    // entity.getClass()
    // NOTE: for some reason lockEx.getPersistentClass() returns null!!!
    // hence comparing by class name...
    if (lockEx.getPersistentClassName().equals(entityClass.getName())) {
        T currentVersion = getById(entity.getId());
        throw new EntityVersionConflictException(lockEx, currentVersion);
    } else {
        throw lockEx;
    }
}

Note the comments. In case of CascadeType.MERGE this will not work like this, the logic would have to be much more complex. I have 1 service per entity type so that service would have to hold reference to all other services and so forth.