JCH
Java Community | Help. Code. Learn.•4d ago
Franscis123$#

Searching DB registers by other field instead PK using JPA

I have a project using JPA without any framework. I want to search registers by others fields like 'username', 'password' instead the primary key. I need to use SQL with JPA to it? 
    public User findUser(Long id) {
        EntityManager em = getEntityManager();
        try {
            return em.find(User.class, id);
        } finally {
            em.close();
        }
    }
    public User findUser(Long id) {
        EntityManager em = getEntityManager();
        try {
            return em.find(User.class, id);
        } finally {
            em.close();
        }
    }
I tried to create the same method in my JPA controller class using a string instead to the id for the search, obviously this give me a error where I see that the method search a numeric PK. But I can't to do something similar?
8 Replies
JavaBot
JavaBot•4d ago
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ayylmao123xdd
ayylmao123xdd•4d ago
i think the best choice would be using jpql to write the query and execute it
dan1st
dan1st•4d ago
em.createQuery() should work or alternatively use a typed query
Franscis123$#
Franscis123$#OP•4d ago
If I need to use PersistenceContext, this will affect to others methods that uses 'em' ?
dan1st
dan1st•4d ago
Didn't you say something about not using a framework? and what do you mean with affecting other methods?
Franscis123$#
Franscis123$#OP•4d ago
Nothing, now I see that 'em' is initialized individually in each method and not globally. 
 public User userByUsername(String username) {
    
    EntityManager em = getEntityManager();

    Query query = em.createQuery("SELECT u FROM User u WHERE u.username = :username");

    query.setParameter("username", username);

    User user;

    try { user = (User ) query.getSingleResult(); } catch (NoResultException e) {

        System.out.println("User not found");
        return null;

    }

    return user;

    }
 public User userByUsername(String username) {
    
    EntityManager em = getEntityManager();

    Query query = em.createQuery("SELECT u FROM User u WHERE u.username = :username");

    query.setParameter("username", username);

    User user;

    try { user = (User ) query.getSingleResult(); } catch (NoResultException e) {

        System.out.println("User not found");
        return null;

    }

    return user;

    }
I build my method like this, what you think?
dan1st
dan1st•4d ago
looks good
JavaBot
JavaBot•4d ago
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