Grails : from HQL to DetachedCriteria Query - grails

Question

Let say I have the following domain model :
class Book {
String title
Set authors
static hasMany = {authors: Author}
}
class Author {
String name
}
The HQL query to retrieve a collection of Author given a query on a title Book:
Author.executeQuery("select distinct author from Book as book join book.authors as author where book.name like ?", ["%groovy%"])
But I would to be able to have the same result a with DetachedCriteria or alike (but is it possible ... ?) and without adding a relationship from Author to Book (otherwise it would pretty obvious)
thanks

Answer 1

This can be done a few ways with criteria or detached Criteria, but a bit easier with regular GORM criteria since it implements the createAlias command that detachedCriteria doesn't as of Grails 2.2.2:
Create Alias In Detached Criteria
Here are both ways:
package bookauthor
import grails.gorm.DetachedCriteria
import grails.orm.HibernateCriteriaBuilder
class MyController {
def index() {
HibernateCriteriaBuilder ac2 = Author.createCriteria()
HibernateCriteriaBuilder criteria2 = Author.createCriteria()
HibernateCriteriaBuilder criteria = Book.createCriteria()
def bookResults = criteria {
projections {
property 'aut.id'
}
createAlias('authors', 'aut')
like('title', '%Groovy%')
}
def dc = new DetachedCriteria(Book).build {
authors {}
like('title', '%Groovy%')
}
def myList = dc.list().collect { it.authors.collect { author -> author.id} }.flatten()
def resultsDetached = criteria2 {
'in'('id', myList )
}
def results = ac2 {
'in'('id', bookResults )
}
log.info("RESULTS: " + results)
log.info("Detached RESULTS: " + resultsDetached)
}
}
You'll see in the logs:
bookauthor.MyController - RESULTS: [bookauthor.Author : 1, bookauthor.Author : 3]
bookauthor.MyController - Detached RESULTS: [bookauthor.Author : 1, bookauthor.Author : 3]

Answer 2

Unfortunately, AFAIK, this is not possible with this query. It's possible with the following ugly query, though:
select author from Author author
where author.id in (select author2.id from Book book
join book.authors as author2
where book.name like :bookName)
For such a simple, non-dynamically composed query, I would stick with your HQL query. If you really need to use Criteria, then this is the corresponding code:
Criteria c = session.createCriteria(Author.class, "author");
DetachedCriteria dc = DetachedCriteria.forClass(Book.class, "book");
dc.createAlias("book.authors", "author2");
dc.add(Restrictions.like("book.name", bookName));
dc.setProjection(Projections.property("author.id"));
c.add(Subqueries.propertyIn("author.id", dc);
List<Author> authors = (List<Author>) c.list();