Hibernate 4 with second level cache: what wrong in my understanding?

hibernate, java, second-level-cache

Solution

The setCacheable method is not available from javax.persistence.Query, so you'll need to add the caching hint to the named query (or call setHint):

@NamedQueries({
@NamedQuery(
    name="SimplePerson.findByName", 
    query="select p from SimplePerson p where p.name = :name", 
    hints = { @QueryHint(name = "org.hibernate.cacheable", value = "true") })
})

That said, using the query cache has jumped the shark, the following article is a must read if you're even going to consider it. These days there are better approaches like the Spring Caching abstraction.

Problem

I have starting to use Hibernate 4 with second level cache. The configuration was very simple according to the documentation: ``` <property name="hibernate.cache.use_second_level_cache" value="true"></property> <property name="hibernate.cache.use_query_cache" value="true"></property> <property name="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.EhCacheRegionFactory"></property> ``` According to my understanding the second level cache should eliminate same queries to the database. I have very simple entity and very simple named query: ``` @Entity @NamedQueries({ @NamedQuery(name="SimplePerson.findByName", query="select p from SimplePerson p where p.name = :name"), }) @Cache(usage = CacheConcurrencyStrategy.READ_WRITE) public class SimplePerson { public static final String FIND_BY_NAME = "SimplePerson.findByName"; @Id @GeneratedValue(strategy = GenerationType.AUTO) private int id; private String name; public SimplePerson() { } public SimplePerson(String name) { this.name = name; } } ``` I run named query 4 times and unfortunately I see that hibernate run it 4 times. ``` EntityManagerFactory emf = Persistence.createEntityManagerFactory("test"); EntityManager em = emf.createEntityManager(); Query query = em.createNamedQuery(SimplePerson.FIND_BY_NAME); query.setParameter("name", "BOB"); List result = query.getResultList(); result = query.getResultList(); result = query.getResultList(); result = query.getResultList(); ``` The output: ``` Hibernate: select simplepers0_.id as id0_, simplepers0_.name as name0_ from SimplePerson simplepers0_ where simplepers0_.name=? Hibernate: select simplepers0_.id as id0_, simplepers0_.name as name0_ from SimplePerson simplepers0_ where simplepers0_.name=? Hibernate: select simplepers0_.id as id0_, simplepers0_.name as name0_ from SimplePerson simplepers0_ where simplepers0_.name=? Hibernate: select simplepers0_.id as id0_, simplepers0_.name as name0_ from SimplePerson simplepers0_ where simplepers0_.name=? ``` What wrong with what wrong in my understanding of the second level cache? Why Hibernate runs the query 4 times? Do I miss some configurations? Thanks in advance, Michael

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