使用hibernate的查詢快取

執行以下程式碼：

String jpql = "FROM User u WHERE u.id = ?";
Query query = entityManager.createQuery(jpql);
query.setParameter(1, 1);
User user = (User) query.getSingleResult();


query = entityManager.createQuery(jpql);
query.setParameter(1, 1);
user = (User) query.getSingleResult();

很顯然會執行兩次查詢

如果想要使用快取，只查詢一次，可以使用setHint

String jpql = "FROM User u WHERE u.id = ?";
Query query = entityManager.createQuery(jpql).setHint(QueryHints.HINT_CACHEABLE, true);
query.setParameter(1, 1);
User user = (User) query.getSingleResult();


query = entityManager.createQuery(jpql).setHint(QueryHints.HINT
 
_CACHEABLE, true);
query.setParameter(1, 1);
user = (User) query.getSingleResult();

注意：這裡的QueryHints是org.hibernate.ejb.QueryHints包下的，並且，使用查詢快取的前提是在配置檔案中配置了啟用查詢快取

<property name="hibernate.cache.use_query_cache" value="true"/>