What are the pros and cons of using Criteria or HQL? The Criteria API is a nice object-oriented way to express queries in Hibernate, but sometimes Criteria Queries are more difficult to understand/build than HQL.
When do you use Criteria and when HQL? What do you prefer in which use cases? Or is it just a matter of taste?
I mostly prefer Criteria Queries for dynamic queries. For example it is much easier to add some ordering dynamically or leave some parts (e.g. restrictions) out depending on some parameter.
On the other hand I'm using HQL for static and complex queries, because it's much easier to understand/read HQL. Also, HQL is a bit more powerful, I think, e.g. for different join types.
There is a difference in terms of performance between HQL and criteriaQuery, everytime you fire a query using criteriaQuery, it creates a new alias for the table name which does not reflect in the last queried cache for any DB. This leads to an overhead of compiling the generated SQL, taking more time to execute.
Regarding fetching strategies [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.
Criteria is an object-oriented API, while HQL means string concatenation. That means all of the benefits of object-orientedness apply:
Since HQL is very much like SQL (which most devs know very well already) then these "don't have to remember" arguments don't carry as much weight. If HQL was more different, then this would be more importatnt.
I usually use Criteria when I don't know what the inputs will be used on which pieces of data. Like on a search form where the user can enter any of 1 to 50 items and I don't know what they will be searching for. It is very easy to just append more to the criteria as I go through checking for what the user is searching for. I think it would be a little more troublesome to put an HQL query in that circumstance. HQL is great though when I know exactly what I want.
HQL is much easier to read, easier to debug using tools like the Eclipse Hibernate plugin, and easier to log. Criteria queries are better for building dynamic queries where a lot of the behavior is determined at runtime. If you don't know SQL, I could understand using Criteria queries, but overall I prefer HQL if I know what I want upfront.
Criteria Api is one of the good concept of Hibernate. according to my view these are the few point by which we can make difference between HQL and Criteria Api
Criteria API is better suited for dynamically generated queries. So, if you want to add WHERE clause filters, JOIN clauses, or vary the ORDER BY clause or the projection columns, then the Criteria API can help you generate the query dynamically in a way that also prevents SQL Injection attacks.
On the other hand, Criteria queries are less expressive and can even lead to very complicated and inefficient SQL queries.
JPQL is the JPA standard entity query language while HQL extends JPQL and adds some Hibernate-specific features.
JPQL and HQL are very expressive and resemble SQL. Unlike Criteria API, JPQL and HQL make it easy to predict the underlying SQL query that's generated by the JPA provider. It's also much easier to review one's HQL queries than Criteria ones.
It's worth noting that selecting entities with JPQL or Criteria API makes sense if you need to modify them. Otherwise, a DTO projection is a much better choice.
If you don't need to vary the entity query structure, then use JPQL or HQL. If you need to change the filtering or sorting criteria or change the projection, then use Criteria API.
However, just because you are using JPA or Hibernate, it doesn't mean you should not use native SQL. SQL queries are very useful and JPQL and Criteria API are not a replacement for SQL.
To use the best of both worlds, the expressivity and conciseness of HQL and the dynamic nature of Criteria consider using Querydsl.
Querydsl supports JPA/Hibernate, JDO, SQL and Collections.
I am the maintainer of Querydsl, so this answer is biased.
For me Criteria is a quite easy to Understand and making Dynamic queries. But the flaw i say so far is that It loads all many-one etc relations because we have only three types of FetchModes i.e Select, Proxy and Default and in all these cases it loads many-one (may be i am wrong if so help me out :))
2nd issue with Criteria is that it loads complete object i.e if i want to just load EmpName of an employee it wont come up with this insted it come up with complete Employee object and i can get EmpName from it due to this it really work bad in reporting. where as HQL just load(did't load association/relations) what u want so increase performance many times.
One feature of Criteria is that it will safe u from SQL Injection because of its dynamic query generation where as in HQL as ur queries are either fixed or parameterised so are not safe from SQL Injection.
Also if you write HQL in ur aspx.cs files, then you are tightly coupled with ur DAL.
Overall my conclusion is that there are places where u can't live without HQL like reports so use them else Criteria is more easy to manage.
For me the biggest win on Criteria is the Example API, where you can pass an object and hibernate will build a query based on those object properties.
Besides that, the criteria API has its quirks (I believe the hibernate team is reworking the api), like:
I tend to use HQL when I want queries similar to sql (delete from Users where status='blocked'), and I tend to use criteria when I don't want to use string appending.
Another advantage of HQL is that you can define all your queries before hand, and even externalise them to a file or so.
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();
so in our case the returned records are maps of needed properties.
Most the answers here are misleading and mention that Criteria Queries are slower than HQL, which is actually not the case.
If you delve deep and perform some tests you will see Criteria Queries perform much better that regular HQL.
And also with Criteria Query you get Object Oriented control which is not there with HQL.
For more information read this answer here.
This post is quite old. Most answers talk about Hibernate criteria, not JPA criteria. JPA 2.1 added CriteriaDelete/CriteriaUpdate, and EntityGraph that controls what exactly to fetch. Criteria API is better since Java is OO. That is why JPA is created. When JPQL is compiled, it will be translated to AST tree(OO model) before translated to SQL.
Another point is that, I see Criteria is more suited for building on top of it and not to be used ditectly in the end-code.
It is more suited to build liberaries using it more than using jpql or hql.
For example I've build spring-data-jpa-mongodb-expressions using Criteria API (the same way spring data QBE do).
I think spring data query generations are using jpaql rather criteria which I don't understand why.
