Thank you very much.
Pere
James Sutherland wrote:
>
> The table creation support is only meant for rapid prototyping, not for
> production data.
>
> The table creation "create" option will only create the tables if they are
> missing. You must use "drop and create" to recreate the database. There
> is no support for altering, but you can do this yourself through your
> databases DDL.
>
>
> snowstone wrote:
>>
>> Hello everybody:
>> I'm using JPA-Toplink in a desktop application, linked to a Postgres DB.
>> I'm following a course and its exercises. I created the tables from the
>> code without problems. The problems come whenever I want to add more
>> attributes to the already existing classes (In the next exercise we
>> create relationships between classes made with new attributes).
>>
>> Having the 2 classes:
>> @Entity
>> public class Autor implements Serializable {
>> @Id
>> private String nombre;
>> private String correo;
>> @OneToMany(mappedBy = "autor")
>> private Collection<Mensaje> mensajes = new HashSet<Mensaje>();
>>
>> //This is the new attribute for the new relationship
>> @OneToMany(mappedBy="autor")
>> private Collection<PaginaHtml> paginas = new HashSet<PaginaHtml>();
>> ...}
>>
>> @Entity
>> public class PaginaHtml implements Serializable {
>>
>> private static final long serialVersionUID = 1L;
>>
>> @Id
>> private String nombreFichero;
>> @Temporal(value = TemporalType.DATE)
>> private Calendar creacion;
>> @Lob
>> private String html;
>> private Encoding encoding;
>> private String extensión;
>>
>> //This is the new attribute for the new relationship
>> @ManyToOne
>> private Autor autor;
>> ...}
>>
>> And the code to link both:
>>
>> public void addAutorPagina(){
>> PaginaHtmlDAO phDAO = new PaginaHtmlDAO (em);
>> AutorDAO autDAO = new AutorDAO (em);
>> List<PaginaHtml> listaPag = new ArrayList();
>> List<Autor> listaAut = new ArrayList();
>>
>> em.getTransaction().begin(); //3
>> listaPag = phDAO.listaPaginas();
>> listaAut = autDAO.listaAutores();
>>
>> if (!listaPag.isEmpty() && !listaAut.isEmpty()){
>> listaPag.get(0).setAutor(listaAut.get(0)); //Update
>> relationship from propietary end (PaginaHtml)
>> listaAut.get(0).addPagina(listaPag.get(0)); //Update
>> relationship from other end
>>
>> }
>> em.getTransaction().commit(); //4
>>
>> }
>>
>> Whenever I do the commit, I get the error from Postgre:
>> "Internal Exception: org.postgresql.util.PSQLException: ERROR: no existe
>> la columna «autor_nombre»" (The column "autor_nombre" doesn't exist.
>>
>> This is done with my Table Generation Strategy (from the PU) set to
>> "Create".
>> If I change this strategy to "Drop and Create", I don't get any errors,
>> and the column "autor_nombre" is created in the table "paginahtml".
>>
>> But for me this is not a solution, since when I drop the table I loose
>> all the data...
>>
>> is that the correct procedure? Every time you change attributes in
>> classes you have to backup your DB, change to "Drop and Create", and then
>> get back the "old data".
>>
>> Or what am I doing wrong?
>>
>> Tank you very much for your time,
>>
>> Pere Serrano
>>
>>
>
>
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