Hibernate Tips: Use the QueryCache to avoid additional queries

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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.

Question:

Hibernate does not use the first- and second-level for queries. Is there any way to cache the result of a query?

Solution:

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());

Learn more:

I get into more details about Hibernate’s 3 different kinds of caches in the Hibernate Performance Tuning Online Training.