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
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。
其他回答
我不想在这里白费口舌,但有一点很重要,那就是Criteria查询现在已被弃用。使用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。
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!
当我不知道哪些输入将用于哪些数据时,我通常使用Criteria。就像在一个搜索表单上,用户可以输入1到50个项目中的任何一个,我不知道他们会搜索什么。在检查用户正在搜索的内容时,很容易将更多内容添加到条件中。我认为在这种情况下放置HQL查询会更麻烦一些。当我确切地知道我想要什么时,HQL是很棒的。
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。