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when is criteria better than HQL or nativeSQL Query?

In my Case after getting a certain list I need to to iterate that list to set some other fields of the POJO class.
if (transportHeaderList.get(i) instanceof TransportHeaderIiss){
transHeadIiss=(TransportHeaderIiss)transportHeaderList.get(i);
customerVendor= tOManagementDAO.getVendorCode(transHeadIiss.getCustVendUid());
}
if(customerVendor!=null){
transHeadIiss.setVendorCode(customerVendor.getCustVendCode());
}
The Above code calls getVendorCode method to get custVendorCode value from the database. The code for getVendorCode is as follows
public CustomerVendorIiss getVendorCode(Long custVendUid) {
List list=new ArrayList();
/* Criteria criteria = sessionFactory.getCurrentSession().createCriteria(CustomerVendorIiss.class);
criteria.add(Restrictions.eq("companyCode",user.getDefaultCompany().getCompanyCode()));
if(custVendUid!=null && custVendUid.intValue()>0)
{
criteria.add(Restrictions.eq("custVendUid",custVendUid));
}
list=criteria.list();*/
UsersIiss user= ApplicationContextProvider.getLoggedInUser();
String sqlQuery="select custVendCode as custVendCode from CustomerVendorIiss where companyCode ='"+ user.getDefaultCompany().getCompanyCode() +"' and custVendUid= "+custVendUid;
Query query = sessionFactory.getCurrentSession().createQuery(sqlQuery);
query.setResultTransformer(Transformers.aliasToBean(CustomerVendorIiss.class));
list=query.list();
if(list.size()>0){
return (CustomerVendorIiss)list.get(0);
}else{
return null;
}
}
When I executed above code with criteria, it took a lot time to get the values from table and set it to POJO class and sometimes I would get java.lang.OutOfMemoryError: Java heap space error . I guess that's because I am not de-allocating the criteria object.
when I executed the above code using createQuery() method I did not run into that issue and all that process of getting and setting was faster.
I want to understand what is that I am doing wrong here?
it would be great to know how and when criteria is better or HQL is better ?
Thank you !!

Actually these queries are different. The second one has an additional restriction
companyCode ='"+ user.getDefaultCompany().getCompanyCode() +"'
So try to add the same to the criteria
criteria.add(Restrictions.eq("companyCode",user.getDefaultCompany().getCompanyCode()));
Also it's not god to concate strings this way to get the query. SQL injection is possible. Use parameters instead.
Criteria and HQL is better than SQL in one case - you need DB independent logic to swap DB when necessary without rewriting code.

Can't cast the result of query to entity

everyone. I'm new to Hibernate. And I'm making desktop application. I have 2 tables: Worker and Ceh (i.e. Department). Relation between them: many-to-one, i.e. 1 Ceh may contain many workers.
I run hql query with inner join to show info about all workers including name of the department and want to show the results in JTable.
The hql query:
private static String query_All_Workers="select W.fio, W.nomer, W.salary, C.name from Worker W Inner Join W.ceh C;
The method that runs query:
try {
Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
Query q = session.createQuery(hql);
List resultList = q.list();
displayResult(resultList);
session.getTransaction().commit();
} catch (HibernateException he) {
he.printStackTrace();
}
The method displayResult(List resultList):
Vector<String> tableHeaders = new Vector<>();
tableHeaders.add("FIO");
tableHeaders.add("Nomer");
tableHeaders.add("Salary");
tableHeaders.add("Ceh");
Vector tableData = new Vector();
for(Object o : resultList) {
Worker worker = (Worker)o;
Vector<Object> oneRow = new Vector<Object>();
oneRow.add(worker.getFio());
oneRow.add(worker.getNomer());
oneRow.add(worker.getSalary());
oneRow.add(worker.getCeh());
tableData.add(oneRow);
}
resultTable.setModel(new DefaultTableModel(tableData, tableHeaders));
And the exception occurs like this:
"java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to
workers.entity.Worker"
It happens because the list contains objects which are results of inner join query. So I don't know how I can correctly cast the object to Worker entity in order to use its getters.

You’re getting the “java.lang.ClassCastException” because you are trying to cast object of type java.lang.Object to custom class Worker:
Worker worker = (Worker)o;
There’s nothing wrong with what you’re trying to do just make sure that the result set returns actually Worker, which is not the case. In your example you are returning resultSet of Objects, because you’re writing regular JDBC select SQL statement.
In order to fix that you will need to checkout Hibernate’s Query Language (HQL) syntax and write HQL query instead of regular JDBC one.
Quick tutorial here http://www.tutorialspoint.com/hibernate/hibernate_query_language.htm
I will advise you do to so from now on, because you will gain the following benefits:
When you write select statements (or any other for that matter) with HQL you think and use Java objects, not DB tables (it helps a lot with table foreign key mappings);
HQL returns whole Java object back since Hibernate will do the necessary conversion for you.
In your case you just need to replace the query_All_Workers with this: “from Worker”. Yup, that’s it! Looks weird but as I said before, Hibernate is taking care of all conversions;
Once you’ve done that, and assuming that your Java class is properly mapped to Hibernate entity, resultSet will contain Workers this time, from which you can easily extract Ceh’s name by using Java getter method:
worker.getCeh.getName();
Also using HQL you will not need to make a second select to Ceh table, just to get the name, like you need to do right now.
Hope that helps.

How to return hibernate collection entities without returning root entity

I would like to get elements of a collection (Set<SheetConfig>) for a set of objects (WorkbookConfig) from Hibernate without getting the primary objects(WorkbookConfig).
The underlying tables look like this:
workbook_config -> workbook_config_sheet_join <- sheet_config
If I just run it in my SQL utility, a successful SQL statement looks like this:
SELECT DISTINCT sheet_config_id FROM sheet_config AS sc
LEFT JOIN workbook_config_sheet_join AS wcsj
ON sc.sheet_config_id = wcsj.sheet_config_id
LEFT JOIN workbook_config AS wc
ON wc.workbook_config_id = wcsj.workbook_config_id
WHERE wc.group_id ="1"
ORDER BY sheet_name;
I would like to do this properly without using HQL.
My UNSUCCESSFUL attempt has resulted in this:
#SuppressWarnings("unchecked")
public List<SheetConfig> findAllForUser() {
List<SheetConfig> sheetConfigs = null;
Session session = getSession();
Criteria crit = session.createCriteria(WorkbookConfig.class)
.add(Restrictions.in(GROUP, getGroupsForUser()))
.setFetchMode(SHEET_CONFIGS, FetchMode.JOIN);
sheetConfigs = (List<SheetConfig>) crit.list();
return sheetConfigs;
}
This is still giving me WorkbookConfigs, but what I would like to do in a single pass is get SheetConfigs. I have spent the day on the Internet trying to find a coherent explanation of the Hibernate API, and I haven't been able to find what I would think is a solution to a fairly common requirement. I can always back out and just do most of the work in Java, but it seems like I should be able to do this with the Hibernate API. I appreciate any help, and also, if you can recommend a reference that explains not simply querying collections, but returning them, I would be grateful.

Did you look into the setProjection method on Criteria?
Using the setProjection method lets you select properties or objects from the executed query.
Hibernate Criteria documentation

Need help creating JPA criteria query

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 work—making 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);

Referring to an earlier aliased field in a criteria query

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.