I'm starting to use JPA with hibernate and I'm having doubts about the HQL query, I did a little research on the hql Query only that I could not understand much. I want to do this select in hql only I did not understand how to transform it into hql
select idUsuario FROM usuarios where login = 'user'
Suppose a mapped and annotated class with JPA / Hibernate that represents Usuario with these fields, reflecting a table you already have in the database:
@Entity
class Usuario {
@Id
private long id;
private String login;
(...)
//getters e setters
}
Now suppose your query method in the database you want to bring a Usuario from a login property:
public Usuario getUsuario(String login) {
//Pegando a sessao (pressupõe que você já tenha o factory de sessão configurado etc.
SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
Session session = sessionFactory.getCurrentSession();
Query query = session.createQuery("from Usuario user where user.login= :login");
query.setString("login", login);
Usuario usuario = (Usuario) query.uniqueResult(); //retorna um Object, por isso o cast obrigatório
}
The important part of your question is here. We define a name for the variable that represents our class (here, user ) and define the property of this class on which we want to base our query ( login , but could be name, age, profession, etc.), accessing the object as we normally do in Java (object.property, that is, user.login ):
Query query = session.createQuery("from Usuario user where user.login= :infoDeLogin");
// Here you link the parameter used in the query with the parameter used in the method.
query.setString("infoDeLogin", login);
See that the query begins with "from Usuario" and not with "select *" , which would normally be expected. This is because, when you want to bring the whole entity, this start is unnecessary, just start with "from" , as done there.