How to get SELECT values and COUNT value with JPA GROUP BY?

Question

If my entity is get as a Man, it have name, id properties, with JPA how I get retrieve result like this query,

entityManager.createQuery("SELECT m.name AS name, COUNT(m) AS total FROM Man AS m GROUP BY m.name ORDER BY m.name ASC"); 

Is there any way to use org.springframework.jdbc.core.RowMapper with JPA?

Answer 1

When you execute this query, instead of getting directly a list of objects like usual, you'll retrieve a list of Object[].

For each array you retrieve, the first element will be the name of the row, the second the count.

I don't think you can use a RowMapper with JPA. RowMapper comes from Spring, which is not the same framework as JPA. Maybe some JPA implementation allow this, but I don't think it is wise to do so.

Edit - Code Example:

List<Object[]> results = entityManager         .createQuery("SELECT m.name AS name, COUNT(m) AS total FROM Man AS m GROUP BY m.name ORDER BY m.name ASC");         .getResultList(); for (Object[] result : results) {     String name = (String) result[0];     int count = ((Number) result[1]).intValue(); }