7

So if my JPA query is like this: Select distinct p from Parent p left join fetch p.children order by p.someProperty

I correctly get results back ordered by p.someProperty, and I correctly get my p.children collection eagerly fetched and populated. But I'd like to have my query be something like "order by p.someProperty, p.children.someChildProperty" so that the collection populated inside each parent object was sub-ordered by someChildProperty.

This seems intuitive when I think in terms of the sql that is actually generated for these calls, but I guess less so when it tries to map back to hierarchical objects.

Brian Deacon
  • 19,494
  • 12
  • 36
  • 40

3 Answers3

17

For preserving order, use TreeSet. As far as, sorting of a collection inside parent is concerned, just do it in your code using Comparator.

Well, try this on your collection definition in your parent entity class. I hope you are getting my point.

You can use this JPA annotation,

@javax.persistence.OrderBy(value = "fieldName")

or this Hibernate specific,

@org.hibernate.annotations.OrderBy(clause = "FIELD_NAME asc")

and you can also use this,

@org.hibernate.annotations.Sort(type = SortType.NATURAL)

or

@org.hibernate.annotations.Sort(type = SortType.COMPARATOR)

In the case of comparator, a comparator must be in place. Other might only work with String collections.

Adeel Ansari
  • 38,068
  • 12
  • 89
  • 127
  • as a generic alternative you can use the javax annotation: @javax.persistence.OrderBy(value = "fieldName") – James A Wilson May 20 '12 at 13:46
  • I tried @javax.persistence.OrderBy(value = "fieldName") where fieldName is an integer. It fetches child collection in descending order and when I use @javax.persistence.OrderBy("fieldName") then it fetches the child collection in ascending order. It is quite strange to me, As per the documentation ASC and DESC should be appended with field name but it is not impacting the results. – Satyam Feb 08 '19 at 06:28
2

If you are using springboot and jpa here's the example

in parent class add the code like below

@OneToMany(mappedBy = "user")
@OrderBy(value = "position desc ")
private List<UserAddresses> userAddresses;

in the above code, position is the field name in UserAddresses Class and desc is the order. You can pass either asc or desc like in sql order by.

Dilli Babu Kadati
  • 69
  • 1
  • 8
1

Adeel basically has this nailed. You can also use those with a List which might be important if your collections contain the same entity more than once.

cliff.meyers
  • 17,342
  • 5
  • 48
  • 66