How to update bean in database on a RequestScoped view?

Question

First of all, sorry for my english. I have a RequestScoped ManagedBean in order to send parameters to other views, without getting the The scope of the object referenced by expression is shorter than the referring managed beans error. I also have in the same RequestScoped view a p:dataTable showing these beans objects, with an update button for each row, that retrieves this bean to another form in the same view to be update with new values.

The problem is, when I hit the submit button to record the new values, another record is created, instead of the older one being updated. Of course, because the bean is killed when the submit button is pressed (RequestScoped), creating a new bean and another record in the DB. How can I fix it in this scope?

I've seen some alternatives using @PostConstruct here, however I'm not entirely sure it would solve my specific problem.

EDIT:

After researching a bit more into this topic, I came to another doubt: I am using the same Bean in both views (in my case, ProjectBean), should I create a new Bean with RequestScoped annotation (something like ProjectIdBean), set the older one to ViewScoped (so I can reproduce updates naturally on my Database), and let this new Bean handle the requests for other views?

Submit button: <p:commandButton value="Gravar" action="#{projetoBean.gravar}" process="@form" update="@form :formTabelaProjetos:tabelaProjetos" />

'Gravar' method:

    public void gravar() {
    System.out.println("Gravando projeto " + this.projeto.getNome());

    ProjetoDAO dao = new ProjetoDAO();

    if (this.projeto.getId() == null) {
        dao.adiciona(this.projeto);
        projetosAtivos = this.getProjetosAtivos();
    } else {
        dao.atualiza(this.projeto);
    }

    this.projeto = new Projeto();
}

Here it is, thanks for your attention. Is there any other snippet of the code that would be useful here? — Felipe Wagner
Have you tried the suggestion you said ? to separate the bean into two beans with different scopes ? (i.e make one bean only for update's purpose) — Omar
Actually I removed the annotation which was causing the error mentioned in the OP, and set up the scope of ProjetoBean to SessionScoped, preserving the same bean to the next page. It is not always a good thing to do, but in my case it's fine, since I won't have other pages with other projects. Thank you for your time, Omar. — Felipe Wagner

David Hladky David Hladky · Accepted Answer · 2018-09-05T09:15:58

You can use request scoped backing bean for updating entities. The problem is, that the request life cycle ends when your page is rendered. So anything you loaded will get discarded. The submit creates another request, that will try to reload resources, but it is a different request than the previous one and for example request parameters often do not contain what the programmer expects. But this is what you found out already. There are two ways how to deal with the problem:

1) use simple getters and setters to set "String, Integer" and similar variables in your request scoped bean, that you use to reconstruct and modify the entity you want to update. It is not convenient for the programmer but request scoped beans save resources of your server.

2) change the scope of your backing bean. Session scope is not ideal, because it can stay in memory for a really long time. And you might realize you need to clean it up manually. Much better is ViewScoped bean as it allows you to work with the entities you loaded over several steps. It gets wiped out when the user leaves the page.

@javax.faces.bean.ViewScoped
@javax.faces.bean.ManagedBean
public class SomethingBean {
    ......
}

How to update bean in database on a RequestScoped view?

1 Answers