如何在JPA中从Expression转换为CriteriaBuilder

Question

I have below code which uses outdated Expression

Criteria criteria = getSession().createCriteria(TagSynonym.class);
criteria.add(Expression.like("title", "%"+piece+"%") );
criteria.setFirstResult(0);
criteria.setMaxResults(maxTagsInResult);
return criteria.list();

I want to achieve same with CriteriaBuilder . Below is what I tried, however it returns an empty array. Please guide what do I miss here. Also guide how to set limit on result.

EntityManager em = this.getEntityManager();
CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
CriteriaQuery<TagSynonym> query = criteriaBuilder.createQuery(TagSynonym.class);

Root<TagSynonym> fromTagsSynonyms = query.from(TagSynonym.class);
Predicate likesTags = criteriaBuilder.equal(fromTagsSynonyms.get(TagSynonym_.title), "%"+piece+"%");
query.select(fromTagsSynonyms).where(likesTags);
return em.createQuery(query).getResultList();

Answer 1

You should use CriteriaBuilder#like() instead of CriteriaBuilder#equal() , to perform like matching.

Predicate likesTags = criteriaBuilder.like(fromTagsSynonyms.get(TagSynonym_.title), "%"+piece+"%");

For the rest your code is basically correct.