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

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/

其他回答

还有另一种方法。我最终创建了一个基于hibernate原始语法的HQL解析器,这样它就可以首先解析HQL,然后动态地注入动态参数或自动为HQL查询添加一些通用过滤器。效果很好!

HQL和criteriaQuery在性能上是有区别的,每次你使用criteriaQuery发起查询时,它会为表名创建一个新的别名,这个别名不会反映在任何DB的最后一个查询缓存中。这会导致编译生成的SQL的开销,需要更多的时间来执行。

关于抓取策略[http://www.hibernate.org/315.html]

Criteria respects the laziness settings in your mappings and guarantees that what you want loaded is loaded. This means one Criteria query might result in several SQL immediate SELECT statements to fetch the subgraph with all non-lazy mapped associations and collections. If you want to change the "how" and even the "what", use setFetchMode() to enable or disable outer join fetching for a particular collection or association. Criteria queries also completely respect the fetching strategy (join vs select vs subselect). HQL respects the laziness settings in your mappings and guarantees that what you want loaded is loaded. This means one HQL query might result in several SQL immediate SELECT statements to fetch the subgraph with all non-lazy mapped associations and collections. If you want to change the "how" and even the "what", use LEFT JOIN FETCH to enable outer-join fetching for a particular collection or nullable many-to-one or one-to-one association, or JOIN FETCH to enable inner join fetching for a non-nullable many-to-one or one-to-one association. HQL queries do not respect any fetch="join" defined in the mapping document.

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。

这里的大多数答案都是误导性的,并提到标准查询比HQL慢,但事实并非如此。

如果你深入研究并执行一些测试,你会发现标准查询比常规HQL执行得更好。

同样,通过Criteria Query,你可以得到HQL所没有的面向对象的控制。

更多信息请阅读这里的答案。

Criteria Api是Hibernate的一个很好的概念。根据我的观点,这些是我们可以区分HQL和Criteria Api的少数点

HQL is to perform both select and non-select operations on the data, but Criteria is only for selecting the data, we cannot perform non-select operations using criteria. HQL is suitable for executing Static Queries, where as Criteria is suitable for executing Dynamic Queries HQL doesn’t support pagination concept, but we can achieve pagination with Criteria. Criteria used to take more time to execute than HQL. With Criteria we are safe with SQL Injection because of its dynamic query generation but in HQL as your queries are either fixed or parametrized, there is no safe from SQL Injection