Does JPA have second-level caching support?

Sonar · **Joined:** Wed Dec 27, 2006 10:03 am **Posts:** 19

Greetings,

My short question is: is there any JPA cache provider that would enable second-level caching in JPA application? Can EHCache\OSCache work with JPA?

Thanks

max · **Posted:** Thu Jan 18, 2007 7:29 am

Hibernate EntityManager is implemented on top of Hibernate Core and Annotations so everythign that is available to hibernate core is available to JPA applications that uses Hibernate EntityManager.

leopinho · **Joined:** Sun Sep 30, 2007 2:58 pm **Posts:** 26

How can I evict some entity from 2nd Level Cache using JPA + Hibernate? Is there any method as below?

"For the second-level cache, there are methods defined on SessionFactory for evicting the cached state of an instance, entire class, collection instance or entire collection role.

sessionFactory.evict(Cat.class, catId); //evict a particular Cat
sessionFactory.evict(Cat.class); //evict all Cats
sessionFactory.evictCollection("Cat.kittens", catId); //evict a particular collection of kittens
sessionFactory.evictCollection("Cat.kittens"); //evict all kitten collections"

How can I do that using EntityManager or EntityManagerFactory?

Thanks!

max · **Posted:** Mon Oct 01, 2007 6:40 am

there is no concept of 2nd lvl cache in JPA spec.

leopinho · **Joined:** Sun Sep 30, 2007 2:58 pm **Posts:** 26

Even the JPA spec does not have the concept of 2nd level cache I can use it with Hibernate as JPA vendor.

I just have to pass the specific properties for cache at persistence.xml and it works.

Code:

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" 
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
          version="1.0">

      <persistence-unit name="SpringJpaPersistenceUnit" transaction-type="RESOURCE_LOCAL">
   
      <!-- A list of vendor-specific properties -->
      <properties>
         <property name="hibernate.cache.use_second_level_cache" value="true"/>
         <property name="hibernate.cache.use_query_cache" value="true"/>
         <property name="hibernate.cache.use_minimal_puts" value="true"/>    
         <property name="hibernate.cache.provider_class" value="org.hibernate.cache.EhCacheProvider"/>
         <property name="hibernate.cache.provider_configuration_file_resource_path" value="META-INF/ehcache.xml"/>         
      </properties>
   </persistence-unit>
</persistence>

I just want to know how to evict the objects cached... Should I do that directly using the Cache API (in my case EhCache API)? I guess this is an ugly solution...

max · **Posted:** Mon Oct 01, 2007 9:33 am

You use an hibernate specific feature that is not available in JPA api so yes you have to use hibernate interfaces/classes for this.

That means:

sessionFactory.evict(Cat.class, catId); //evict a particular Cat
sessionFactory.evict(Cat.class); //evict all Cats
sessionFactory.evictCollection("Cat.kittens", catId); //evict a particular collection of kittens
sessionFactory.evictCollection("Cat.kittens"); //evict all kitten collections"

if you start using ehcache api you will end up with an inconsistent cache.

leopinho · **Joined:** Sun Sep 30, 2007 2:58 pm **Posts:** 26

Is there any better way to access sessionFactory instance than below?

I would be useful if the interface HibernateEntityManager would have some getSessionFactory method...

Code:

@PersistenceContext
protected EntityManager entityManager;
...
HibernateEntityManager hibernateEntityManager = (HibernateEntityManager)entityManager;
Session session = null;
try {
   session = hibernateEntityManager.getSession();
   SessionFactory sessionFactory = session.getSessionFactory();
   sessionFactory.evict(ApplicationLog.class);
} finally {
   session.close();
}

max · **Posted:** Mon Oct 01, 2007 12:57 pm

Look for getDelegate() in jpa/annotation docs.

leopinho · **Joined:** Sun Sep 30, 2007 2:58 pm **Posts:** 26

Yeah, but this method does not help some much. I still have to get the sessionFactory using a Session instance...

New code:

Code:

@PersistenceContext
protected EntityManager entityManager;
...
Session session = (Session)entityManager.getDelegator();
try {
   SessionFactory sessionFactory = session.getSessionFactory();
   sessionFactory.evict(ApplicationLog.class);
} finally {
   session.close();
}

Do you have other idea? Thanks again!

max · **Posted:** Mon Oct 01, 2007 1:28 pm

ask in jpa forum - i can't remember the supported method.

leopinho · **Joined:** Sun Sep 30, 2007 2:58 pm **Posts:** 26

Unfortunately I've already checked the JPA api and there is no other method.

As I said before it would be useful if the interface HibernateEntityManager would have some getSessionFactory method...

max · **Posted:** Mon Oct 01, 2007 1:37 pm

*ask in the JPA forum*

leopinho · **Joined:** Sun Sep 30, 2007 2:58 pm **Posts:** 26

A better solution!

"( (HibernateEntityManagerFactory) emf).getSessionFactory()
and then the evict method you want
_________________
Emmanuel"

Thanks Emmanuel!