JPA 2.0 Criteria and grouping of Predicates

问题

I encounter problem with Hibernate EntityManager 3.5.3-Final when it comes to composite predicates.

Example (not actual code snippet, but the idea should be clear):

CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
Predicate predicate1 = criteriaBuilder.conjunction();
Predicate predicate2 = criteriaBuilder.conjunction();
// These are Boolean expression with common Root
predicate1.getExpressions().add(expression1);
predicate1.getExpressions().add(expression2);
predicate2.getExpressions().add(expression3);
predicate2.getExpressions().add(expression4);
//...
query.where(criteriaBuilder.or(predicate1, predicate2));

Now, I would expect something like:

SELECT ... FROM ... WHERE (expression1 AND expression2) OR (expression3 AND expression4)

However I end up with:

SELECT ... FROM ... WHERE expression1 AND expression2 OR expression3 AND expression4

Am I doing something awfully wrong or is it Hibernate issue?

回答1:

According to the SQL specification, both statements mean the same thing. It doesn't matter whether the statement contains the () or not, so Hibernate doesn't use them. The order of precedence is like this, similar to 1+2*3 is the same as 1+(2*3).

来源：https://stackoverflow.com/questions/3382678/jpa-2-0-criteria-and-grouping-of-predicates