How to use JPA2's @Cacheable instead of Hibernate's @Cache

Question

Typically , I use Hibernate's @Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE) to cache an @Entity class , and it works well.

In JPA2 , there's another @Cacheable annotation that seems to be the same functionality with Hibernate's @Cache. To make my entity class independent of hibernate's package , I want to give it a try. But I cannot make it work. Each time a simple id query still hits the DB.

Can anybody tell me where goes wrong ? Thanks.

Entity class :

@Entity //@Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE) @Cacheable(true)  public class User implements Serializable {  // properties } 

Test class :

@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations={"classpath:app.xml"}) @TransactionConfiguration(transactionManager="transactionManager") public class UserCacheTest {   @Inject protected UserDao userDao;    @Transactional   @Test   public void testGet1()   {     assertNotNull(userDao.get(2L));   }    @Transactional   @Test   public void testGet2()   {     assertNotNull(userDao.get(2L));   }    @Transactional   @Test   public void testGet3()   {     assertNotNull(userDao.get(2L));   } } 

The test result shows each "get" hits DB layer (with hibernate.show_sql=true).

Persistence.xml :

<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.format_sql" value="true" /> <property name="hibernate.use_outer_join" value="true"/>  <property name="hibernate.cache.provider_class" value="org.hibernate.cache.SingletonEhCacheProvider"/> <property name="hibernate.cache.use_second_level_cache" value="true"/> <property name="hibernate.cache.use_query_cache" value="true"/> 

JPA code :

@Override public T get(Serializable id) {   return em.find(clazz, id); } 

Answer 1

According to the JPA 2.0 specification, if you want to selectively cache entities using the @Cacheable annotation, you're supposed to specify a <shared-cache-mode> in the persistence.xml (or the equivalent javax.persistence.sharedCache.mode when creating the EntityManagerFactory).

Below, a sample persistence.xml with the relevant element and properties:

<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_2_0.xsd" version="2.0">   <persistence-unit name="FooPu" transaction-type="RESOURCE_LOCAL">     <provider>org.hibernate.ejb.HibernatePersistence</provider>     ...     <shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>     <properties>       ...       <property name="hibernate.cache.provider_class" value="org.hibernate.cache.SingletonEhCacheProvider"/>       <property name="hibernate.cache.use_second_level_cache" value="true"/>       <property name="hibernate.cache.use_query_cache" value="true"/>     </properties>   </persistence-unit> </persistence> 

Note that I've seen at least one issue HHH-5303 related to caching. So the above is not guaranteed :)

References

• Hibernate EntityManager reference guide
  • 2.2.1 Packaging
• JPA 2.0 Specification
  • Section 3.7.1 "The shared-cache-mode Element"
  • Section 11.1.7 "Cacheable Annotation"