Count JPA and Invalid Path

jpa

After poking around Stack Overflow I found the following solution for counting problem. My requirement is to get the total number of matching rows, and return the first ten for pagination purposes.

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<T> cq = cb.createQuery(clazz);
CriteriaQuery<Long> counterCq = cb.createQuery(Long.class);
counterCq.select(cb.count(counterCq.from(clazz)));
Predicate predicate= null;
Predicate predicate1 = null;
Root<T> root = cq.from(clazz);
for (Map.Entry<String, String> e : filters.entrySet()){
    predicate = cb.and(cb.like(root.<String>get(e.getKey()), e.getValue()+ "%"));
}
if(predicate != null){
    cq.where(predicate);
    counterCq.where(predicate);
}
int pn = ( em.createQuery(counterCq).getSingleResult()).intValue();
logger.debug("number of pages is {}", pn);
setRowCount(pn);

if(sortField !=null && !sortField.trim().equals("")){
    if(sortOrder == SortOrder.DESCENDING){
        cq.orderBy(cb.desc(root.get(sortField)));
    } else{
        cq.orderBy(cb.asc(root.get(sortField)));
    }
}

Query q = em.createQuery(cq);
q.setFirstResult(first);
q.setMaxResults(first+ps);
List<T> cats= (List<T>)q.getResultList();

This snippet makes hibernate to through

java.lang.IllegalArgumentException: org.hibernate.hql.ast.QuerySyntaxException: Invalid path: 'generatedAlias1.title' [select count(generatedAlias0) from Media as generatedAlias0 where generatedAlias1.title like :param0]

It seems like cq.from(clazz) cannot be applied for the other query.
Now my question: Is there a way to use the same predicate in both queries?

Best Answer

Your predicate list isn't assembled correctly. You have to 'and' predicates together into a single expression. I also prefer to build my predicate before performing the select for better readability.

Here's a refactor of your code to achieve the correct results:

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<T> cq = cb.createQuery(clazz);
Root<T> root = cq.from(clazz);

// build predicate list - conjuction starts us with an empty 'and' predicate
Predicate predicate = cb.conjunction();
for (Map.Entry<String, String> e : filters.entrySet()) {
    predicate = cb.and(predicate, cb.like(root.get(e.getKey()), e.getValue() + "%"));
}

// query total count
CriteriaQuery<Long> counterCq = cb.createQuery(Long.class);
counterCq.select(cb.count(root)).where(predicate);

int pn = (em.createQuery(counterCq).getSingleResult()).intValue();
logger.debug("number of pages is {}", pn);
setRowCount(pn);

// query results
cq.select(root).where(predicate);

if(sortField !=null && !sortField.trim().equals("")) {
    if(sortOrder == SortOrder.DESCENDING) {
        cq.orderBy(cb.desc(root.get(sortField)));
    }
    else {
        cq.orderBy(cb.asc(root.get(sortField)));
    }
}

TypedQuery<T> q = em.createQuery(cq);
q.setFirstResult(first);
q.setMaxResults(first+ps);
List<T> list = q.getResultList();
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