Question

Okay, so I have several tables

• Vote
• Contest
• ContestSegment
• ContestRegistration
• Submittable
• User

The relationship is that a Submittable may be submitted to a contest via creating a ContestRegistration, which is tied to a ContestSegment, which is tied to a Contest.

A Vote has a User and a reference to a ContestRegistration that the Vote relates to.

Pretty simple.

Now, the idea is that I want to hit a RESTful service which checks to see if I’ve already voted on one of the ContestRegistrations in a contest.

Everything is working except for the desired result.

The JPQL that I’m running looks like this:

SELECT DISTINCT v 
FROM Vote v, Contest c 
JOIN v.user vu 
LEFT JOIN c.segments cs 
LEFT JOIN cs.registrations csr 
LEFT JOIN csr.votes csrv 
WHERE vu.id = :userId 
AND cs.beginDate < CURRENT_TIMESTAMP 
AND cs.endDate > CURRENT_TIMESTAMP 
AND c.id = :contestId

The method looks like:

public Boolean hasUserVoted(User user, Contest contest){
    StringBuffer query = new StringBuffer()
    .append("SELECT DISTINCT v from Vote v, Contest c ")
    .append("JOIN v.user vu LEFT JOIN c.segments cs LEFT JOIN cs.registrations csr LEFT JOIN csr.votes csrv ")

    .append("WHERE vu.id = :userId ")
    .append("  ")
    .append("AND cs.beginDate < CURRENT_TIMESTAMP AND cs.endDate > CURRENT_TIMESTAMP AND c.id = :contestId ");
    Boolean hasVoted = true;
    try{
    Vote vote = (Vote)entityManager.createQuery(query.toString())
        .setParameter("userId", user.getId())
        .setParameter("contestId", contest.getId()).getSingleResult();
    }catch(NoResultException nre){
        hasVoted = false;
    }

    return hasVoted;
}

But when I return, no matter what I plug in, I’m always getting a true back (meaning I’ve already voted). For instance, I’ve voted on contest#1, but I haven’t voted on contest#2. If I plug in the value for contest#2, then I still get a true back. I’m fairly new to JPQL, so any help you can provide would be awesome! Thanks!

Answer 1

With the use of left joins in your JPQL, it will return true unless the contest don’t exists. Its sounds like the csr.votes should be a normal join.