使用Criteria或HQL的优点和缺点是什么?Criteria API是一种在Hibernate中表达查询的面向对象的好方法,但有时Criteria queries比HQL更难理解/构建。
什么时候使用标准,什么时候使用HQL?在哪些用例中您更喜欢什么?还是说这只是个人口味的问题?
使用Criteria或HQL的优点和缺点是什么?Criteria API是一种在Hibernate中表达查询的面向对象的好方法,但有时Criteria queries比HQL更难理解/构建。
什么时候使用标准,什么时候使用HQL?在哪些用例中您更喜欢什么?还是说这只是个人口味的问题?
当前回答
另一点是,我认为Criteria更适合在它的基础上构建,而不是在最终代码中直接使用。
它更适合使用它来构建库,而不是使用jpql或hql。
例如,我使用Criteria API构建了spring-data-jpa-mongodb-expressions(与spring数据QBE的方式相同)。
我认为spring数据查询代使用jpaql而不是标准,我不明白为什么。
其他回答
对于动态查询,我更喜欢使用条件查询。例如,根据某些参数,动态地添加一些排序或保留一些部分(例如限制)要容易得多。
另一方面,我使用HQL进行静态和复杂的查询,因为它更容易理解/阅读HQL。此外,我认为HQL更强大一些,例如对于不同的连接类型。
HQL可能会导致SQL注入等安全问题。
为了两全其美,HQL的表达性和简洁性以及Criteria的动态特性可以考虑使用Querydsl。
Querydsl支持JPA/Hibernate, JDO, SQL和Collections。
我是Querydsl的维护者,所以这个答案是有偏见的。
We used mainly Criteria in our application in the beginning but after it was replaced with HQL due to the performance issues. Mainly we are using very complex queries with several joins which leads to multiple queries in Criteria but is very optimized in HQL. The case is that we use just several propeties on specific object and not complete objects. With Criteria the problem was also string concatenation. Let say if you need to display name and surname of the user in HQL it is quite easy (name || ' ' || surname) but in Crteria this is not possible. To overcome this we used ResultTransormers, where there were methods where such concatenation was implemented for needed result. Today we mainly use HQL like this:
String hql = "select " +
"c.uuid as uuid," +
"c.name as name," +
"c.objective as objective," +
"c.startDate as startDate," +
"c.endDate as endDate," +
"c.description as description," +
"s.status as status," +
"t.type as type " +
"from " + Campaign.class.getName() + " c " +
"left join c.type t " +
"left join c.status s";
Query query = hibernateTemplate.getSessionFactory().getCurrentSession().getSession(EntityMode.MAP).createQuery(hql);
query.setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);
return query.list();
因此,在本例中,返回的记录是所需属性的映射。
条件是指定利用第二级查询缓存中的特殊优化的自然键查找的唯一方法。HQL没有任何方法来指定必要的提示。
你可以在这里找到更多信息:
http://tech.puredanger.com/2009/07/10/hibernate-query-cache/