• Post Reply Bookmark Topic Watch Topic
  • New Topic

JPA: Count object relations in n:m relationship - do I need a native query?  RSS feed

Posts: 436
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

I am stuck at n:m relationships. I want to count the number of relations with JPA.

Prerequisites: JPA (1.x atm), Hibernate as JPA provider, configuration by JPA annotations.


Item - Category (Student - Course would do also )

This results in a quite simple database schema:

- item(id,...)
- category(id, label...)
- item_category(item_id, category_id)

I just want to count the number of articles that belong to a category. Simple with a native query:

But a native query feels like an impurity. No IDE checks, no refactoring support, no startup checks by the persistence provider... I would prefer something in JPQL but I can't see how to access the "entity-less" relationship table.

Alternatively I could build an object for the relationship. Seems plausible, as I do work with it's elements.

Are those the ways to go or am I missing something important?

Thank you.
It is sorta covered in the JavaRanch Style Guide.
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!