ForumServiceImpl.java

@Service
public class ForumServiceImpl
        implements ForumService {
 
    @PersistenceContext
    private EntityManager entityManager;
 
    @Override
    @Transactional
    public Post newPost(String title, String... tags) {
        Post post = new Post();
        post.setTitle(title);
 
        post.getTags().addAll(
            entityManager.createQuery("""
                select t
                from Tag t
                where t.name in :tags
                """, Tag.class)
            .setParameter("tags", Arrays.asList(tags))
            .getResultList()
        );
 
        entityManager.persist(post);
 
        return post;
    }
 
    @Override
    @Transactional(readOnly = true)
    public List<Post> findAllPostsByTitle(String title) {
        return entityManager.createQuery("""
            select p
            from Post p
            where p.title = :title
            """, Post.class)
        .setParameter("title", title)
        .getResultList();
    }
}