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POJPA 2.0: count for arbitrary CriteriaQuery?
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copied!<p>I am trying to implement the following convenience method:</p> <pre><code>/** * Counts the number of results of a search. * @param criteria The criteria for the query. * @return The number of results of the query. */ public int findCountByCriteria(CriteriaQuery<?> criteria); </code></pre> <p>In Hibernate, this is done by </p> <pre><code>criteria.setProjection(Projections.rowCount()); </code></pre> <p>What is the equivalent to the above in JPA? I found numerous simple count examples, but none of them made use of a CriteriaQuery whose row count should be determined.</p> <p><strong>EDIT:</strong></p> <p>I unfortunately found out that @Pascal's answer is not the correct one. The problem is very subtle and only shows up when you use joins:</p> <pre><code>// Same query, but readable: // SELECT * // FROM Brain b // WHERE b.iq = 170 CriteriaQuery<Person> query = cb.createQuery(Person.class); Root<Person> root = query.from(Person.class); Join<Object, Object> brainJoin = root.join("brain"); Predicate iqPredicate = cb.equal(brainJoin.<Integer>get("iq"), 170); query.select(root).where(iqPredicate); </code></pre> <p>When calling <code>findCountByCriteria(query)</code>, it dies with the following exception:</p> <pre><code>org.hibernate.hql.ast.QuerySyntaxException: Invalid path: 'generatedAlias1.iq' [select count(generatedAlias0) from xxx.tests.person.dom.Person as generatedAlias0 where generatedAlias1.iq=170] </code></pre> <p>Is there any other way to provide such a <code>CountByCriteria</code> method?</p>

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