Force Hibernate to read database and not return cached entity

Question

I am using Hibernate and Spring for my web application.

In database operation, Hibernate is caching entities and returning them in next request without reading the actual database. I know this will reduce the load on database and improve performance.

But while this app still under construction, I need to load data from database in every request (testing reason).

Is there any way to force database read?

I became sure about the caching from this log4j message.

Returning cached instance of singleton bean 'HelloController'
DEBUG [http-bio-8080-exec-42] - Last-Modified value for [/myApp/../somePageId.html] is: -1

Solution 1

session.refresh(entity) or entityManager.refresh(entity) (if you use JPA) will give you fresh data from DB.

Solution 2

Do the read within a new transaction.

For example:

...
MyDTO myDTO = fetchMyDTOById(daoId);
...
@Transactional(readOnly = true, propagation = Propagation.REQUIRES_NEW)
private MyDTO fetchMyDTOById(Long dtoId) {
    return repository.findById(dtoId);
}

Solution 3

• Call refresh entity session.refresh(entity)

  or

• Open new session then call session2.get(EntityClass.class,id) it will pull the entity from the database

      Session session2=sessionFactory.openSession();                  
      EntityClass entity=(EntityClass) session2.get(EntityClass.class, id);
  

Solution 4

Please call EntityManger.clear() method, and then call repository.find() or repository.findOne() as per your requirement to select the updated data from database.

@PersistentContext EntityManager em;
@Autowired EntityReporisitory rep;
....
....
@Transactional
public void method(){
....
....
em.clear();// This line will clear the current value of entity
Entity e = rep.find(example);// In this line data will be loaded freshly from DB
....
....
}

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Comments

[Saif]

i am not using JPA. so do i need to change session.get() to session.refresh()? or if there is a way to check if it is coming from cache .?

[Predrag Maric]

No, you should use session.refresh() after session.get() because it only works with attached entities. To check if an entity is already loaded, this thread has some suggestions, but nothing reliable imho.

[Adam Siemion]

the trick with this approach is that when the entity does not exist in the database, but exists in the cache, calling refresh() throws org.hibernate.UnresolvableObjectException: No row with the given identifier exists

[Predrag Maric]

@adamsiemion Yes, that is something one should be aware of.

[danidemi]

I had the same problem described in the question. With JPA it seems that entityManager.clear() discard in a single operation the whole cache.

[Alkanshel]

This isn't really satisfactory for retrieving multiple entities--won't refresh on every single one just create a separate query for each? I'd prefer if the initial query itself just bypassed the cache. I'm doing query.setHint("javax.persistence.cache.retrieveMode", CacheRetrieveMode.BYPASS) ... but this doesn't seem to work either. Annoying cache!

[Dragas]

You're using Hibernate, which implements JPA, meaning you use JPA.