Syntax to query two fields in a table with JPA

Question

Referencing JPQL, it's not clear to me exactly how to query a table.

What I want is, if it exists, the @Entity Note for a given messagId and group, but I don't understand the syntax.

How do I specify the messageId and group for the below query?

public void persist(Msg message) {
    LOG.info("\t" + message);
    LOG.info("isOpen?" + em.isOpen());
    em.getTransaction().begin();
    int id = message.getId();
    Query q = em.createQuery("SELECT  n "
            + "FROM Notes n WHERE n.messageId = :messageId "
            + "AND n.group = :group");
    List results = q.getResultList();
    em.getTransaction().commit();
    for (Object o : results) {
        LOG.info("object is \n\n" + o);
    }
}

}

Answer 1

Use setParameter(String name, Object value)

q.setParameter("messageId", id).setParameter("group", group);

To make it better, use TypedQuery

public void persist(Msg message) {
    LOG.info("\t" + message);
    LOG.info("isOpen?" + em.isOpen());
    em.getTransaction().begin();
    int id = message.getId();
    TypedQuery<Note> q = em.createQuery("SELECT  n "
            + "FROM Notes n WHERE n.messageId = :messageId "
            + "AND n.group = :group", Note.class);
    q.setParameter("messageId", id).setParameter("group", group);
    List<Note> results = q.getResultList();
    em.getTransaction().commit();
    for (Note o : results) {
        LOG.info("object is \n\n" + o);
    }
}

Answer 2

You need to set the parameters on the query using setParameter().

See, http://en.wikibooks.org/wiki/Java_Persistence/Querying#Parameters