I have the following structure...
Entity A
- ...
- Collection<B> c (#OneToMany)
Entity B
- ...
- Date d
I want the queryResult to be ordered by the Date d via an orderBy-Statement in my criteriaQuery. How can I achieve this?
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<A> cq = cb.createQuery(A.class);
Root<A> r = cq.from(A.class);
cq.select(r);
// orderBy-Statement -> cq.orderBy(cb.desc(r.get("c.d")).as(Date.class)));
// Error: javax.servlet.ServletException: javax.ejb.EJBException: java.lang.IllegalArgumentException: Unable to resolve attribute [c.d] against path
List<A> l = em.createQuery(cq).getResultList();
Is it possible to have the ordering in the query?
If not, i'm supposed to write a method for ordering my resultList afterwards, right?
Well, all in all I wasn't able to figure out how to use the orderBy-Statement I want. But Now I'm satisfied with an alternative approach (and in my opinion an even better one!):
Fetching the needed data from the database (unordered)
creating a datamodel and using it in the GUI
doing the sorting/ordering on the datamodel/GUI
By the way: I'm using the Primefaces.org-framework. Saves me a lot of work^^
What about this one?
cq.orderBy(cb.desc(r.get("c").get("d")));
Related
I try to do the following inside a Spring Boot application : create a native query and page it so it can returns a page of a given number of elements from a #RestController.
Here's the snippet of my code, where em is the #PersistanceContext EntityManager, and the repository method is the following, knowing that queryString is the native query :
Query searchQuery = em.createNativeQuery(this.queryString, MyEntity.class);
List<MyEntity> resultsList = searchQuery.getResultList();
return new PageImpl<>(resultsList, PageRequest.of(index,size), resultsList.size());
My problem is that the Page returned has a content of the complete query result, not a content of the size of size parameter inside the PageRequest.of.
Has anybody faced the same issue and could give a working example on how to paginate a nativeQuery please ?
Thanks for your help
You are mixing Spring Data JPA (Pageable) with JPA EntityManager. You can't do that. If you are already using a native query then simply put the pagination in the query. You can use what your database supports, for example the standard:
SELECT [a_bunch_of_columns]
FROM dbo.[some_table]
ORDER BY [some_column_or_columns]
OFFSET #PageSize * (#PageNumber - 1) ROWS
FETCH NEXT #PageSize ROWS ONLY;
this is example of using native query with pagination:
#Query("SELECT c FROM Customer As c INNER JOIN Offer as f on f.id=c.specialOffer.id inner join User As u on u.id=f.user.id where u.id=?1 And c.status=?2")
Page<Customer> getAllCustomerToShop(Integer shopId,String status,Pageable pageable)
and then you can call it as:
getAllCustomerToShop(shopId,"status",PageRequest.of(index, PAGE_SIZE));
Modify your code as follows
Query searchQuery = em.createNativeQuery(this.queryString, MyEntity.class)
.setFirstResult(pageable.getPageNumber() * pageable.getPageSize())
.setMaxResults(pageable.getPageSize());
I have created two entities in JPA, Listing and ItemType - these exist in a many-to-many relationship (Hibernate auto-generates a junction table). I'm trying to find the best way to create a query which accepts a dynamic list of item type Strings and returns the IDs of all listings which match the specified item types, but I am a recent initiate in JPA.
At present I'm using JpaRepository to create relatively simple queries. I've been trying to do this using CriteriaQuery but some close-but-not-quite answers I've read elsewhere seem to suggest that because this is in Spring, this may not be the best approach and that I should be handling this using the JpaRepository implementation itself. Does that seem reasonable?
I have a query which doesn't feel a million miles away (based on Baeldung's example and my reading on WikiBooks) but for starters I'm getting a Raw Type warning on the Join, not to mention that I'm unsure if this will run and I'm sure there's a better way of going about this.
public List<ListingDTO> getListingsByItemType(List<String> itemTypes) {
List<ListingDTO> listings = new ArrayList<>();
CriteriaQuery<Listing> criteriaQuery = criteriaBuilder.createQuery(Listing.class);
Root<Listing> listing = criteriaQuery.from(Listing.class);
//Here Be Warnings. This should be Join<?,?> but what goes in the diamond?
Join itemtype = listing.join("itemtype", JoinType.LEFT);
In<String> inClause = criteriaBuilder.in(itemtype.get("name"));
for (String itemType : itemTypes) {
inClause.value(itemType);
}
criteriaQuery.select(listing).where(inClause);
TypedQuery<Listing> query = entityManager.createQuery(criteriaQuery);
List<Listing> results = query.getResultList();
for (Listing result : results) {
listings.add(convertListingToDto(result));
}
return listings;
}
I'm trying to understand how best to pass in a dynamic list of names (the field in ItemType) and return a list of unique ids (the PK in Listing) where there is a row which matches in the junction table. Please let me know if I can provide any further information or assistance - I've gotten the sense that JPA and its handling of dynamic queries like this is part of its bread and butter!
The criteria API is useful when you need to dynamically create a query based on various... criteria.
All you need here is a static JPQL query:
select distinct listing from Listing listing
join listing.itemTypes itemType
where itemType.name in :itemTypes
Since you're using Spring-data-jpa, you just need to define a method and annotate it with #Query in your repository interface:
#Query("<the above query>")
List<Listing> findByItemTypes(List<String> itemTypes)
I am trying to use Spring Data JPA Specificaiton to query data, but I got some problem here.
The Java code is as below:
List<NoticeEntity> studentNoticeEntityList = noticeRepository
.findAll((root, criteriaQuery, criteriaBuilder) -> {
criteriaQuery.distinct(true);
root.fetch(NoticeEntity_.contentEntitySet, JoinType.LEFT);
Predicate restrictions = criteriaBuilder.conjunction();
SetJoin<NoticeEntity, UserNoticeEntity> recipientNoticeJoin = root
.join(NoticeEntity_.recipientNoticeEntitySet, JoinType.INNER);
recipientNoticeJoin.on(criteriaBuilder.equal(
recipientNoticeJoin.get(UserNoticeEntity_.recipientStatus), NoticeRecipientStatus.Unread));
Join<UserNoticeEntity, WeChatUserEntity> recipientUserJoin = recipientNoticeJoin
.join(UserNoticeEntity_.user);
restrictions = criteriaBuilder.and(restrictions,
criteriaBuilder.equal(recipientUserJoin.get(WeChatUserEntity_.id), id));
// recipientNoticeJoin.fetch(UserNoticeEntity_.user, JoinType.INNER);
return restrictions;
});
When I comment the code "recipientNoticeJoin.fetch(UserNoticeEntity_.user, JoinType.INNER);", it is working fine, but when I un-comment this, I will get error:
org.hibernate.QueryException: query specified join fetching, but the owner of the fetched association was not present in the select list
So, I am wondering if join fetch is supported by using Specification way, or there is something wrong with my code.
I know there is another way by using #Query("some hql"), but somehow I just prefer to use the Specification way.
Thanks a lot.
The error specifies that you're missing an entity from your select list. Try this:
criteriaQuery.multiselect(root, root.get(NoticeEntity_.recipientNoticeEntitySet);
Also, hibernate may run a count query first to determine the number of results, and this can cause the above error. You can avoid this breaking by checking the return type of the query before adding the fetch.
Eager fetching in a Spring Specification
I am using LinqPad to test my query. This query works when the LInqPad connection is to my database (LInq to SQL) but it does not work when I change the connection to use my Entity Framework 5 Model.dll. (Linq to Entity). This is in C#.
I have two tables called Plan and PlanDetails. Relationship is one Plan to many PlanDetails.
var q = from pd in PlanDetails
select new {
pd.PlanDetailID,
ThePlanName = (from p in this.Plans
where p.PlanID == pd.PlanID
select p.PlanName)
};
var results = q.ToList();
q.Dump(); //This is a linqpad method to output the result.
I get this error "NotSupportedException: Unable to create a constant value of type 'Domain.Data.Plan'. Only primitive types or enumeration types are supported in this context." Any ideas why this only works with Linq to SQL?
basically it means you are using some complex datatype inside the query for comparison.
in your case i suspect from p in this.Plans where p.PlanID == pd.PlanID is the culprit.
And it depends on DataProvider. It might work for Sql Data Provider, but not for SqlCE data Provider and so on.
what you should do is to convert your this.Plans collection into a primitive type collection containing only the Ids i.e.
var integers = PlanDetails.Plans.Select(s=>s.Id).ToList();
and then use this list inside.
var q = from pd in PlanDetails
select new {
pd.PlanDetailID,
ThePlanName = (from p in integers
where p == pd.PlanID
select pd.PlanName)
};
I got this error when i was trying to null check for a navigational property in the entity framework expression
I resolved it by not using the not null check in the expression and just using Any() function only.
protected Expression<Func<Entities.Employee, bool>> BriefShouldAppearInSearchResults(
IQueryable<Entities.Employee> briefs, string username)
{
var trimmedUsername = NameHelper.GetFormattedName(username);
Expression<Func<Entities.Employee, bool>> filterExpression = cse =>
cse.Employee.Cars.All(c =>
c.Employee.Cars!=null && <--Removing this line resolved my issue
c.Employee.Cars.Any(cur => cur.CarMake =="Benz")));
return filterExpression;
}
Hope this helps someone!
This is a Linqpad bug if you like (or a peculiarity). I found similar behaviour myself. Like me, you may find that your query works with an ObjectContext, but not a DbContext. (And it works in Visual Studio).
I think it has to do with Linqpad's inner structure. It adds MergeAs (AppendOnly) to collections and the context is a UserQuery, which probably contains some code that causes this bug.
This is confirmed by the fact that the code does work when you create a new context instance in the Linqpad code and run the query against this instance.
If the relationship already exists.
Why not simply say.
var q = from pd in PlanDetails
select new {
pd.PlanDetailID,
ThePlanName = pd.Plan.PlanName
};
Of course i'm assuming that every PlanDetail will belong to a Plan.
Update
To get better results from LinqPad you could tell it to use your own assembly (which contains your DbContext) instead of the default Datacontext it uses.
DynamicObject LINQ query with the List compiles fine:
List<string> list = new List<string>();
var query = (from dynamic d in list where d.FirstName == "John" select d);
With our own custom class that we use for the "usual" LINQ compiler reports the error "An expression tree may not contain a dynamic
operation":
DBclass db = new DBclass();
var query = (from dynamic d in db where d.FirstName == "John" select d);
What shall we add to handle DynamicObject LINQ?
Does DBClass implement IEnumerable? Perhaps there is a method on it you should be calling to return an IEnumerable collection?
You could add a type, against which to write the query.
I believe your problem is, that in the first expression, where you are using the List<>, everything is done in memory using IEnumerable & Link-to-Objects.
Apparently, your DBClass is an IQueryable using Linq-to-SQL. IQueryables use an expression tree to build an SQL statement to send to the database.
In other words, despite looking much alike, the two statements are doing radically different things, one of which is allowed & one which isn't. (Much in the way var y = x * 5; will either succeed or fail depending on if x is an int or a string).
Further, your first example may compile, but as far as I can tell, it will fail when you run it. That's not a particular good benchmark for success.
The only way I see this working is if the query using dynamic is made on IEnumerables using Link-to-Objects. (Load the full table into a List, and then query on the list)