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JPA 2.0 EclipseLink Check for Unique

I have a column like unique = true .. in the exam class .... I found that since transactions are automatic, so for forced use I use em.commit ()

However, I would like to know how to check if it is unique. Querying an exception is not a solution, because it may be an attempt after verification due to consistency ....

What is the best way to check uniqness?

List<Exam_Normal> exam_normals = exam.getExam_Normal();
    exam.setExam_Normal(null);

    try {
        em.persist(exam);
        em.flush();

        Long i = 0L;
        if (exam_normals != null) {
            for (Exam_Normal e_n : exam_normals) {
                i++;
                e_n.setItem(i);
                e_n.setId(exam);
                em.persist(e_n);
            }
        }
    } catch (Exception e) {
        System.out.print("sfalma--");
    }
}

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3 answers

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