Artem Vereschaka Artem Vereschaka - 1 month ago 18
Java Question

Clear Hibernate 2nd level cache after manually DB update

Shortly, I have an entity mapped to view in DB (Oracle) with enabled 2nd level Cache (read only strategy) -- ehcache.

If I manually update some column in DB -- cache will not be updated.

I did not find any ways to do this. Only if updates will be done through Hibernate entity.

May I somehow implement this feature?

Maybe Job to monitor table (or view)? Or maybe there is some method to notify Hibernate about change in DB in concrete table.

Thanks for future answers!

Answer

According to Hibernate JavaDoc, you can use org.hibernate.Cache.evictAllRegions() :

evictAllRegions() Evict all data from the cache.

Using Session and SessionFactory:

Session session = sessionFactory.getCurrentSession();

if (session != null) {
    session.clear(); // internal cache clear
}

Cache cache = sessionFactory.getCache();

if (cache != null) {
    cache.evictAllRegions(); // Evict data from all query regions.
}

1) If you need update only one entity (if directly from db you will update only certain entities) not whole session, you can use

evictEntityRegion(Class entityClass) Evicts all entity data from the given region (i.e.

2) If you have a lot of entities, that can be updated directly from db you can use this method that evicts all entities from 2nd level cache (we can expose this method to admins through JMX or other admin tools):

/**
 * Evicts all second level cache hibernate entites. This is generally only
 * needed when an external application modifies the game databaase.
 */
public void Evict2ndLevelCache() {
    try {
        Map<String, ClassMetadata> classesMetadata = sessionFactory.getAllClassMetadata();
        for (String entityName : classesMetadata.keySet()) {
            logger.info("Evicting Entity from 2nd level cache: " + entityName);
            sessionFactory.evictEntity(entityName);
        }
    } catch (Exception e) {
        logger.logp(Level.SEVERE, "SessionController", "evict2ndLevelCache", "Error evicting 2nd level hibernate cache entities: ", e);
    }
}

3) here another apporche described here for postgresql+hibernate, I think similar you can do for Oracle like this