Add Sort implementations that use JPA Metamodel API and/or QueryDsl API [DATAJPA-12] about spring-data-jpa

[spring-projects-issues]

Nemanja Nedic commented

Have you considered adding an implementation that uses JPA Path interface or something equivalent? This is important in cases where we have a parent-child relationship and want to sort by parent field while selecting child entities

[spring-projects-issues]

Oliver Drotbohm commented

This is what JPA Metamodel actually means :). What do you exactly mean with parent? If the parent object is reachable from the child object then a new Sort("parent.foo", Direction.ASC) should do the trick with the current String-based implementation

[spring-projects-issues]

Stevo Slavić commented

It doesn't work and at the moment we believe issue is in hades/spring-data-jpa ( http://redmine.synyx.org/boards/2/topics/221 ) and not JPA implementation we're using (Hibernate). We think that hades/spring-data-jpa should do additional processing when creating queries with sort using dot notation. We'll try to create a simple reproducible example/test

[spring-projects-issues]

Nemanja Nedic commented

I would recommend to use additional parsing in the toJpaOrder method of QueryUtils class. Something like this:

private static javax.persistence.criteria.Order toJpaOrder(Order order, Root<?> root, CriteriaBuilder cb) {
	Expression<?> expression = null;
	String pathString = order.getProperty();
	String[] pathElements = pathString.split(".");
	int pathSize = pathElements.length;

	if (pathSize > 1) {
		Join<Object, Object> path = root.join(pathElements[0]);
		for (int i = 1; i < pathSize - 1; i++) {
			path = path.join(pathElements[0]);
		}
		expression = path.get(pathElements[pathSize - 1]);
	} else {
		expression = root.get(pathString);
	}
	return order.isAscending() ? cb.asc(expression) : cb.desc(expression);
}

[spring-projects-issues]

Nemanja Nedic commented

There are some bugs in my example above. This one is tested and works for us:

private static javax.persistence.criteria.Order toJpaOrder(Order order,
		Root<?> root, CriteriaBuilder cb) {
	Expression<?> expression = null;
	String pathString = order.getProperty();
	String[] pathElements = pathString.split("\\.");
	int pathSize = pathElements.length;

	if (pathSize > 1) {
		Join<Object, Object> path = root.join(pathElements[0]);
		for (int i = 1; i < pathSize - 1; i++) {
			path = path.join(pathElements[i]);
		}
		expression = path.get(pathElements[pathSize - 1]);
	} else {
		expression = root.get(pathString);
	}
	return order.isAscending() ? cb.asc(expression) : cb.desc(expression);
}

[spring-projects-issues]

Oliver Drotbohm commented

Okay, it seems we were talking about different things here. This ticket is more about a special Sort implementation that takes Path parameters instead of String instances as this would allow usage of generated metamodel classes for sort expressions.

I'll be applying your patch nonetheless as it seems to be a more accurate interpretation of the spec than the current version

[spring-projects-issues]

Stevo Slavić commented

Note: Patch was not tested (yet) when path element references @Embedded @Embeddable property

[spring-projects-issues]

Oliver Drotbohm commented

Consolidated implementation derived from that ticket with some code we already had in JpaQueryCreator in course of fixing DATAJPA-103

[spring-projects-issues]

Thomas Darimont commented

Added PR: #54

[spring-projects-issues]

Thomas Darimont commented

Please revise