I am trying to write a distinct criteria query, using:
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<CorporateNews> query = criteriaBuilder.createQuery(CorporateNews.class);
Root<CorporateNews> root = query.from(CorporateNews.class);
query.select(root).distinct(true);
return (List<CorporateNews>) entityManager.createQuery(query).getResultList();
However, this method is not working. The data further contain duplicates.
Anyone know how to fix it?
I call out this method later in the REST API. I get the result:
[{"category":"Cinema"},{"category":"Cinema"},{"category":"Music"}]
However, I would get without repetition of data and so something like this:
[{"category":"Cinema"},{"category":"Music"}]
Related
Spring/Hibernate/MySQL/JPA here. I have the following code:
public void setOrdering(
SearchRequest searchRequest,
CriteriaQuery query,
CriteriaBuilder builder,
Root<? extends MyEntity> root) {
String sortParam = "reportedOn";
Expression expression = builder.selectCase()
.when(builder.isNull(root.get(sortParam)), root.get(sortParam))
.otherwise(root.get(sortParam));
Order order = (searchRequest.isAscending())
? builder.asc(expression)
: builder.desc(expression);
query.orderBy(order);
}
Basically, I'm trying to implement the CriteriaBuilder/JPA equivalent of:
SELECT
*
FROM
mytable
WHERE
<lots of predicates here>
ORDER BY reported_on IS NULL, reported_on <ASC/DESC>
I already have the WHERE predicates added, I'm just struggling with the query.orderBy(...).
At runtime, when searchRequest.isAscending() is false, the results come back working just fine, with the records that contain a null reported_on value ordered at the end of the results.
But if searchRequest.isAscending() is true, the NULLS LAST attempt does not appear to work at all.
You're mixing up the Spring and JPA APIs, here query is from the JPA API so you need to sort using something like:
CriteriaBuilder cb = ...
Root root = ...
query.orderBy(cb.asc(root.get("reportedOn")));
It does not look like JPA's CriteriaBuilder supports NULLS LAST. I actually got this working using a SQL "hack":
String sortParam = "reportedOn";
Order order = (searchRequest.isAscending())
? builder.desc(builder.neg(root.get(sortParam)))
: builder.desc(root.get(sortParam));
query.orderBy(order);
Basically ORDER BY -reported_on DESC does the same thing as ORDER BY reported_on ASC but it sorts records with NULL reported_on values all the way to the bottom of the search results, which is what NULLS LAST is supposed to do.
I am have a problem where i need to join two tables using the LEAST and GREATEST functions, but using JPA CriteriaQuery. Here is the SQL that i am trying to duplicate...
select * from TABLE_A a
inner join TABLE_X x on
(
a.COL_1 = least(x.COL_Y, x.COL_Z)
and
a.COL_2 = greatest(x.COL_Y, x.COL_Z)
);
I have looked at CriteriaBuilder.least(..) and greatest(..), but am having a difficult time trying to understand how to create the Expression<T> to pass to either function.
The simplest way to compare two columns and get the least/greatest value is to use the CASE statement.
In JPQL, the query would look like
select a from EntityA a join a.entityXList x
where a.numValueA=CASE WHEN x.numValueY <= x.numValueZ THEN x.numValueY ELSE x.numValueZ END
and a.numValueB=CASE WHEN x.numValueY >= x.numValueZ THEN x.numValueY ELSE x.numValueZ END
You can code the equivalent using CriteriaBuilder.selectCase() but I've never been a big fan of CriteriaBuilder. If requirements forces you to use CriteriaBuilder then please let me know and I can try to code the equivalent.
CriteriaBuilder least/greatest is meant to get the min/max value of all the entries in one column. Let's say you want to get the Entity that had the alphabetically greatest String name. The code would look like
CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery query = cb.createQuery(EntityX.class);
Root<EntityX> root = query.from(EntityX.class);
Subquery<String> maxSubQuery = query.subquery(String.class);
Root<EntityX> fromEntityX = maxSubQuery.from(EntityX.class);
maxSubQuery.select(cb.greatest(fromEntityX.get(EntityX_.nameX)));
query.where(cb.equal(root.get(EntityX_.nameX), maxSubQuery));
I created a sample Spring Data JPA app that demonstrates these JPA examples at
https://github.com/juttayaya/stackoverflow/tree/master/JpaQueryTest
It turns out that CriteriaBuilder does support calling LEAST and GREATEST as non-aggregate functions, and can be accessed by using the CriteriaBuilder.function(..), as shown here:
Predicate greatestPred = cb.equal(pathA.get(TableA_.col2),
cb.function("greatest", String.class,
pathX.get(TableX_.colY), pathX.get(TableX_.colZ)));
I have to write that HQL query:
FROM Sending adp WHERE adp.id = (SELECT MAX (adpw.id) FROM Sending adpw WHERE adpw.place = adp.place)
I have to use Criteria API and I can't manage it. Query returns last sendings from all places in database and it works very well but now I have to transform it to Criteria. The only thing I managed is to show just one place with following code:
Criteria criteria = getSession().createCriteria(
Sending.class);
criteria.setFetchMode("place", FetchMode.JOIN);
DetachedCriteria maxId = DetachedCriteria.forClass(Sending.class).setProjection(Projections.max("id"));
criteria.add(Property.forName("id").eq(maxId));
Could you help me? Thanks in advance!!
Sorry for answering my own question, but I found the solution.
I forgot that Subqueries can be correlated with themselves. I realized my query with following code:
Criteria criteria = getSession().createCriteria(Sending.class);
DetachedCriteria dc = DetachedCriteria.forClass(Sending.class, "adpw");
dc.add(Restrictions.eqProperty("adpw.place", "adp.place"));
dc.setProjection(Projections.max("id"));
criteria.add(Property.forName("id").eq(dc));
criteria.setMaxResults(count).setFirstResult(start);
return criteria.list();
Everything works now very well.
I'm building my first Java EE web application using Glassfish and JSF. I'm fairly new to the criteria query and I have a query I need to perform but the javaee6 tutorial seems a little thin on examples. Anyway, I'm having a hard time creating the query.
Goal: I want to pull the company with the most documents stored.
Companies have a OneToMany relationship with Documents.
Documents has a ManyToOne relationship with several tables, the "usertype" column distinguishes them.
MySQL query:
SELECT USERID, COUNT(USERID) AS CNT
FROM DOCUMENTS
WHERE USERTYPE="COMPANY"
GROUP BY USERID
ORDER BY CNT DESC
Thanks
--update--
Based on user feedback, here is what I have so far:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Documents> cqry = cb.createQuery(Documents.class);
//Intersting Stuff
Root<Documents> root = cqry.from(Documents.class);
Expression userid = root.get("userID");
Expression usertype = root.get("userType");
Expression count = cb.count(userid);
cqry.multiselect(userid, count);
Predicate userType = cb.equal(usertype, "COMPANY");
cqry.where(userType);
cqry.groupBy(userid);
cqry.orderBy(cb.desc(count));
//more boilerplate
Query qry = em.createQuery(cqry);
List<Documents> results = qry.getResultList();
The error I get is:
Exception Description: Partial object queries are not allowed to maintain the cache or be edited. You must use dontMaintainCache().
Typical error, means nothing to me!
Your query doesn't return a complete entity object as you're only selecting two fields of the given table (this is why you're getting an error that says yadayadapartialyadayada).
Your solution is almost right, here's what you need to change to make it workâmaking it partial.
Instead of a plain CriteriaQuery<...> you have to create a tuple CriteriaQuery<..> by calling CriteriaBuilder.createTupleQuery(). (Basically, you can call CriteriaBuilder.createQuery(...) and pass Tuple.class to it as an argument. Tuple is a sort of wildcard entity class.)
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Tuple> cq= cb.createTupleQuery();
Root<Documents> root = cq.from(Documents.class);
Expression<Integer> userId = root.get("USERID");
Expression<String> userType = root.get("USERTYPE");
Expression<Long> count = cb.count(userId);
cq.multiselect(userId.alias("USERID"), count.alias("CNT"));
cq.where(cb.equal(userType, "COMPANY");
cq.groupBy(userId);
cq.orderBy(cb.desc(count));
TypedQuery<Tuple> tq = em.createQuery(cq);
for (Tuple t : tq.getResultsList()) {
System.out.println(t.get("USERID"));
System.out.println(t.get("CNT"));
}
(Accessing fields of a Tuple gave me an error if I didn't use aliases for them (in multiselect(...)). This is why I've used aliases, but this can be tackled more cleanly by using JPA 2's Metamodel API, which is described in the specification quite thoroughly. )
The documentation for CriteriaQuery.multiselect(...) describes the behaviour of queries using Tuple objects more deeply.
If you are using Hibernate, this should work:
ProjectionList pl = Projections.projectionList()
.add(Projections.groupProperty("userid"))
.add(Projections.property("userid"))
.add(Projections.count("userid"));
Criteria criteria = session.createCriteria(Document.class)
.add(Restrictions.eq("usertype",usertype))
.setProjection(pl)
.addOrder(Order.desc("cnt"));
Hope it helps!
Take a look into this easy tutorial. It uses JPA2 and Criteria
http://www.jumpingbean.co.za/blogs/jpa2-criteria-api
Regards!
You need to add a constructor to Documents with only userid and count because you will need it on:
cqry.multiselect(userid, count);
In this query:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Tuple> q = cb.createTupleQuery();
// FROM GamePlayedEvent gpe
Root<GamePlayedEvent> gpe = q.from(GamePlayedEvent.class);
// SELECT gameId, COUNT(*) AS count, AVG(duration)
// AS avDur, AVG(rewardCurrency) AS avCur, AVG(rewardXP) avXp
q.select(cb.tuple(
gpe.<String>get("gameId"),
cb.count(gpe).alias("count"),
cb.avg(gpe.<Double>get("duration")).alias("avDur"),
cb.avg(gpe.<Integer>get("rewardCurrency")).alias("avCur"),
cb.avg(gpe.<Integer>get("rewardXp")).alias("avXp")
));
// WHERE loginTime BETWEEN ...
q.where(cb.between(gpe.<Date>get("time"), fromTime, toTime));
// GROUP BY gameId
q.groupBy(gpe.<String>get("gameId"));
// ORDER BY count DESC
q.orderBy(cb.desc(???));
How can I add the ORDER BY count DESC, referring to the "count" defined in the SELECT clause?
What if you just captured the count expression, and used it directly?
Expression event_count = cb.count(gpe);
q.select(cb.tuple(
gpe.<String>get("gameId"),
event_count,
...
));
q.orderBy(cb.desc(event_count));
I came across the same problem today but none of the suggested solutions worked for me because I needed to reuse the expression not only in the order by clause but also in the group by clause.
One obvious solution would be to create a view on the database level but this is a bit clumsy, creates an unnecessary subquery and even not possible if the db user isn't granted enough privileges. A better option which I ended up implementing is to write something like this
q.select(cb.tuple(
gpe.<String>get("gameId"),
cb.count(gpe),
...
)).groupBy(cb.literal(2)).orderBy(cb.literal(2));
The first downside of this approach is that the code is errorprone. The other drawback is that the generated sql query contains ordinal position notation, which works on some databases (like postgresql or mariadb) but doesn't work on others (like sql server). In my case, however, I found this to be the best option.
Tested on jpa 2.1 with hibernate 5.2.3 as a provider and postgresql 9.6.
Even though the Pro JPA 2 book describes that the alias method can be used to generate a sql query alias (on page 251) I have had no success with making it work with neither EclipseLink or Hibernate. For your question I would say that your orderBy line should read:
q.orderBy(cb.desc(cb.count(gpe));
if it was supported by the different vendors.
As far as my research goes it seams that the alias method is only used for naming elements in the tuble used in the select (so only for projection).
I have one question though. Why would you want to use the JPA Criteria API for this query. It (the query) seams to be static in nature so why not use JPQL where you can define your query aliases directly.
Have you tried setting up a projection with an alias?
criteria.setProjection(Projections.projectionList()
.add(Projections.count("item.id"), "countItems"));
criteria.addOrder(Order.desc("countItems"));
For a sum aggregation field I have the following code which worked for me:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<T> cq = cb.createQuery(entity);
Root<T> root = cq.from(entity);
cq.orderBy(cb.desc(cb.sum(root.get(orderByString))));
// orderByString is string entity field that is being aggregated and which we want to put in orderby clause as well.