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Hibernate Tips is a new series of posts in which I describe a quick and easy solution for common Hibernate questions. If you have a question you like me to answer, please leave a comment below.
Hibernate does not use the first- and second-level for queries. Is there any way to cache the result of a query?
Hibernate also supports the QueryCache, which can store the result of a query. You need to activate it in the persistence.xml file by setting the parameter hibernate.cache.use_query_cache to true and defining a hibernate.cache.region.factory_class (see l. 12-13).
<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.1" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"> <persistence-unit name="my-persistence-unit"> ... <properties> ... <! – configure caching – > <property name="hibernate.cache.use_query_cache" value="true"/> <property name="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.EhCacheRegionFactory"/> </properties> </persistence-unit> </persistence>
And you also need to activate caching for the specific query of which you want to cache the results by calling the setCacheable of the Hibernate-specific Query interface with the parameter true.
Session s = (Session) em.getDelegate(); Query q = s.createQuery("SELECT a FROM Author a WHERE id = :id"); q.setParameter("id", 1L); q.setCacheable(true); log.info(q.uniqueResult());
I get into more details about Hibernate’s 3 different kinds of caches in the Hibernate Performance Tuning Online Training.
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