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Handling null values from database in spring jpa

This works fine:
#Repository
public interface VoteDao extends CrudRepository <Vote, Long> {
#Query(value = "select sum(points) from votes where siteuserid= ?1", nativeQuery = true)
int countBySiteUser(#Param("user") SiteUser user);
}
Except in case when there are no votes yet that the result is NULL and the problem is that I do not know how to handle that case of checking when it is Null since the query does no return anything when I ask...
System.out.println("!!!!: PROPOSAL VoteService: " + voteDao.countBySiteUser(user));
Should it print a Null value for that sysout? The DAO is supposed to answer with a NULL value, but it is not. I would be able to handle that NULL if provided, but it does not.
Thanks in advance for your help!

Use COALESCE to handle null as 0, which correspond to what you actually mean.
#Query(
value = "SELECT COALESCE(SUM(points), 0) FROM votes WHERE siteuserid = ?1",
nativeQuery = true)
int countBySiteUser(#Param("user") SiteUser user);
... or another solution with a programmatic approach:
// Integer instead of int to add the "null" handling
#Query(
value = "SELECT SUM(points) FROM votes WHERE siteuserid = ?1",
nativeQuery = true)
Integer countBySiteUser(#Param("user") SiteUser user);
Usage:
Integer count = voteDao.countBySiteUser(user);
if (count == null) {
count = 0;
}
System.out.println("!!!!: PROPOSAL VoteService: " + count);
The COALESCE solution seems better to me. But as #EJP said, it will depend on your needs.

JPQL collection parameter - mismatch the expected type

A bit of context: I have a Spring app with Hibernate.
I want to get all Location entities filtered by ID so I pass a set of IDs as parameter to the query. The problem is that on the query.setParameter("ids", locationIds); row I get the following error:
:Parameter value element [728331] did not match expected type [java.lang.Long (n/a)]
I am confused since the set I am giving is set of Long values. So I assume no explicit casting should be done when passing it as parameter, right? Does anyone has suggestion what is causing the error?
I checked other similar questions but I didn't find one that solve my issue.
#Repository
#Transactional(propagation = Propagation.MANDATORY)
public class LocationDao {
#PersistenceContext
private EntityManager em;
public List<Location> getLocationsByIds(Set<Long> locationIds) {
if (locationIds == null || locationIds.isEmpty()) {
return null;
}
final TypedQuery<Location> query =
em.createQuery("FROM Location l WHERE l.id IN :ids", Location.class);
query.setParameter("ids", locationIds);
return query.getResultList();
}
}
#Entity
#Table(name = "location")
public class Location {
#Id
private Long id;
// other fields
}
EDIT: Hibernate entity manager version: 4.3.8.Final

Found the problem. The locationIds are not exactly Set<Long> locationIds but Set<BigInteger>.
I retrieve the IDs through a native query since I need to perform recursive search in locations. Although I cast it to List<Long> it is actually returns a List<BigInteger>. Here is the code:
private static final String SQL_FIND_LOCATION_AND_CHILDREN_IDS =
" WITH RECURSIVE result_table(id) AS ( "
+ " SELECT pl.id "
+ " FROM location AS pl "
+ " WHERE pl.id = :parentId "
+ "UNION ALL "
+ " SELECT c.id "
+ " FROM result_table AS p, location AS c "
+ " WHERE c.parent = p.id "
+ ") "
+ "SELECT n.id FROM result_table AS n";
#SuppressWarnings("unchecked")
public List<Long> getLocationAndAllChildren(Long parentId) {
final Query query = em.createNativeQuery(SQL_FIND_LOCATION_AND_CHILDREN_IDS);
query.setParameter("parentId", parentId);
return query.getResultList();
}
Then I can just take the long value of the BigInteger since I am sure the values fit in Long's size.
#SuppressWarnings("unchecked")
public List<Long> getLocationAndAllChildren(Long parentId) {
final Query query = em.createNativeQuery(SQL_FIND_LOCATION_AND_CHILDREN_IDS);
query.setParameter("parentId", parentId);
final List<BigInteger> resultList = query.getResultList();
final List<Long> result = new ArrayList<Long>();
for (BigInteger bigIntId : resultList) {
result.add(bigIntId.longValue());
}
return result;
}
Thanks to all for replying and sorry for wasting your time.

JPA TypedQuery error

I get the error "Cannot create TypedQuery for query with more than one return using requested result type"
for the following query using JPA on Glassfish, any ideas what is wrong here? I want to get the latest debit record with a certain debit status.
entityManager.createQuery("select dd, MAX(dd.createdMillis) from T_DEBIT dd" +
" where dd.debitStatus in (:debitStatus)" +
" and dd.account = :account" , Debit.class)
.setParameter("debitStatus", false)
.setParameter("account", account)
.getSingleResult();

A generic parameter is normally specified for a TypedQuery. If you declared a TypedQuery you would use an Object[] as the generic parameter for the TypedQuery, since you are projecting columns and not returning a complete entity.
However, since you have not declared a TypedQuery (your using a concise coding style), you need to change Debit.class to Object[].class since your not selecting an object, but instead only two fields.
Object[] result = entityManager.createQuery("select dd, MAX(dd.createdMillis) from T_DEBIT dd" +
" where dd.debitStatus in (:debitStatus)" +
" and dd.account = :account" , Object[].class) //Notice change
.setParameter("debitStatus", false)
.setParameter("account", account)
.getSingleResult();
Executing this query will return a Object[] where each index in the Object[] corresponds with a field in your select statement. For example:
result[0] = dd
result[1] = max(dd.createdMillis)
To avoid using the Object[] you could create a new class to retrieve these values in a more strongly typed fashion. Something like:
public class Result {
String dd;
Date createdMillis;
public Result(String dd, Date createdMillis) {
super();
this.dd = dd;
this.createdMillis = createdMillis;
}
public String getDd() {
return dd;
}
public void setDd(String dd) {
this.dd = dd;
}
public Date getCreatedMillis() {
return createdMillis;
}
public void setCreatedMillis(Date createdMillis) {
this.createdMillis = createdMillis;
}
}
Then in your JPQL statement you could call the constructor:
Result result = entityManager.createQuery("select NEW fully.qualified.Result(dd, MAX(dd.createdMillis)) from T_DEBIT dd" +
" where dd.debitStatus in (:debitStatus)" +
" and dd.account = :account" , Result.class)
.setParameter("debitStatus", false)
.setParameter("account", account)
.getSingleResult();
Recently, I have blogged about this exact topic. I encourage you to view this video tutorial I created: https://tothought.cloudfoundry.com/post/16

Filtering results in a JPQL query

I am trying to make "filter" search for all questions in my database. Now I get a exception telling me that I can't compare enum values with string. Is it because I don't use the fully qualified package name of wher the enum type is declared? If so, is it better ways than hard-coding the package name?
Exception Description: Error compiling the query [SELECT q FROM
Question q WHERE q.status = 'APPROVED'], line 1, column 40: invalid
enum equal expression, cannot compare enum value of type
[app.utility.Status} with a non enum value of type
[java.lang.String].
public List<Question> all(Status status, ViewOption viewOption) {
String jpql = "SELECT q FROM Question q ";
boolean isWhereClauseAdded = false;
if (status != Status.ALL) {
if (!isWhereClauseAdded) {
jpql += "WHERE ";
}
jpql += "q.status = '" + status + "'";
}
if (viewOption != ViewOption.ALL) {
if (!isWhereClauseAdded) {
jpql += "WHERE ";
}
// Check if 'AND' operator is needed.
if (status != Status.ALL) {
jpql += " AND ";
}
switch (viewOption) {
case ONLY_IMAGES:
jpql += "q.image != ''";
break;
case NO_IMAGES:
jpql += "q.image = '' ";
break;
}
}
TypedQuery<Question> query = entityManager.createQuery(jpql,
Question.class);
return query.getResultList();
}

The right thing to do would be to use a query parameter:
String jpql = "select ... where q.status = :status";
Query query = em.createQuery(jpql).setParameter("status", status);
Rather than creating your query dynamically be concatenating query parts, you should also use the Criteria API, which has been designed with this goal in mind.

Can you try changing:
jpql += "q.status = '" + status + "'";
To:
jpql += "q.status = app.utility.Status." + status;

CriteriaAPI - GroupBy - Not Generated

I'm tearing my hair out over something that may very well be very simple,
but I just cant get it right.
My GroupBy clause is not being added to the SQL generated by EclipseLink.
Have tried many different orders and variations of the code below.
public List<Orders> findOrdersEntitiesBySearch(int maxResults, int firstResult, String column1, String column2, String key, boolean searchOrder) {
EntityManager em = getEntityManager();
try {
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Orders> cq = cb.createQuery(Orders.class);
Root<Orders> order = cq.from(Orders.class);
Join<Orders, Products> prod = order.join("productsCollection");
// Where like key
if (column1 != null && column2 != null) {
if (searchOrder) {
cq.where(cb.or(cb.like(cb.lower(order.get(column1).as(String.class)), "%" + key.toLowerCase() + "%"), cb.like(cb.lower(order.get(column2).as(String.class)), "%" + key.toLowerCase() + "%")));
} else {
cq.where(cb.or(cb.like(cb.lower(prod.get(column1).as(String.class)), "%" + key.toLowerCase() + "%"), cb.like(cb.lower(prod.get(column2).as(String.class)), "%" + key.toLowerCase() + "%")));
}
} else {
if (searchOrder) {
cq.where(cb.like(cb.lower(order.get(column1).as(String.class)), "%" + key.toLowerCase() + "%"));
} else {
cq.where(cb.like(cb.lower(prod.get(column1).as(String.class)), "%" + key.toLowerCase() + "%"));
}
}
// Order By
List<Order> orderByList = new ArrayList<Order>();
orderByList.add(cb.desc(order.get("ordDate")));
orderByList.add(cb.desc(order.get("pkOrdID")));
cq.orderBy(orderByList);
// Select
cq.select(order);
// Group by
//cq.groupBy(order.get("pkOrdID"));
//Expression<Integer> grouping = order.get("pkOrdID").as(Integer.class);
Expression<String> grouping = order.get("pkOrdID").as(String.class);
cq.groupBy(grouping);
Query q = em.createQuery(cq);
q.setMaxResults(maxResults);
q.setFirstResult(firstResult);
return q.getResultList();
} finally {
em.close();
}
}
The code compiles an runs fine, I get results but my GroupBy clause is not included.
As a nasty quickfix, I am running the list returned through a function to remove the duplicates until I can find the solution.
Thanks in advance for any assistance,
David

For clarity, re-written as regular JPQL query, you currently have something like this:
SELECT o
FROM Orders o JOIN o.productsCollection p
WHERE ...
GROUP BY o.pkOrdID...
There are two issues here. First, the group by is not correct, because you can't group by on a single column when a full object is selected - just as with standard SQL, all selected columns that are not aggregates must be listed in the group by. The second issue is that you don't need group by here at all. See below for your options:
Since you don't use any aggregate functions here, what you actually want is simply:
SELECT DISTINCT o
FROM Orders o JOIN o.productsCollection p
WHERE ...
Therefore, simply drop the group-by from your criteria API query, and use cq.distinct(true) instead.
If you really need group by with aggregate functions for a different query, instead of grouping on the primary key of a selected object, in JPA you group by the object itself. A simple JPQL example might be:
SELECT o, sum(p.quantity)
FROM Orders o JOIN o.productsCollection p
WHERE ...
GROUP BY o
In your query, this would be cq.groupBy(order).
Btw. I have no idea why eclipse link simply ignores your group by here instead of reporting an error. Which version are you using?