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

对于动态条件查询,我们可以根据我们的输入构造查询..在Hql查询是静态查询的情况下,一旦我们构造,我们就不能改变查询的结构。

其他回答

HQL可能会导致SQL注入等安全问题。

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/

HQL更容易阅读,更容易使用Eclipse Hibernate插件等工具进行调试,也更容易记录日志。条件查询更适合构建动态查询,其中许多行为都是在运行时确定的。如果你不知道SQL,我可以理解使用Criteria查询,但总的来说,如果我知道我想要什么,我更喜欢HQL。

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。

对于动态条件查询,我们可以根据我们的输入构造查询..在Hql查询是静态查询的情况下,一旦我们构造,我们就不能改变查询的结构。