Create form based on object dynamically

[Andre Froes]

Hello everyone,

Is it possible to create a form based on my object dynamically?

Example:

@ManagedBean(name="person")
@RequestScoped
@Entity
public class Person{
  @Column(length=100)
  private String name;
  @Column(length=2)
  private int age;
  public Person(){}
...get/set
}

Based on that object, I want to create a form that will read it and create the form with a repetition structure, ui:repeat for example:

<ui:repeat var="p" value="#{person}">
  <h:outputLabel value="#{p.name}"/>
  <h:inputText value="#{don'tKnow}"/>
</ui:repeat>

Can that be done? I managed to do it with scriplet and annotation based on Generic, but in JSF2 I'm not managing to do so.

[Tim Holloway]

I generally don't encourage dynamic forms. One of JSF's strengths is that instead of having to have programmers painstakingly create and debug the UI from logic (one of the annoying things about frameworks such as java awt), you can have non-JSF people "paint" a form in declarative View Template Language (xhtml) and let JSF do all the dirty work. Some people, alas think that they're too clever for that, but the results are generally awkward and expensive.

Beside, there's a simpler way (in JSF, there usually is).

<h:dataTable var="person" value="#{mybean.people}">
   <h:column><h:outputLabel="Name"/></h:column>
   <h:column><h:inputText id="person" value="#{person.name}"/></h:column>
</h:dataTable>

You get as many rows as there are elements in the "mybean.people" datamodel object.

[Andre Froes]

Let me add a scenario here to make more understandable what I'm aiming for. I am going to have several tables (studying purpose), such as person, cars, fruits, etc., and I'll eventually add some info there, but I don't want to create a view for each one, I'll pass thru URL param the kind of object that I want to add. Ex.:

http://localhost:8085/MyStudy/persist-new-object.jsf?objKind=person

based on objKind, I'll access the corresponding bean and load all fields within it regarding its rules, length(), etc,.

I already did that implementation that you showed me, but it is no for the same purpose that I'm after, it would be an n-1 relation. I'm just aiming to generate the form and then persist. My brain is boiling already with it

[Tim Holloway]

There are 3 common expressions of this concept, which itself transcends JSF.

1. Dynamic application form construction. People end up essentially re-creating the framework, only with more complexity, less flexibility, less reliability and no vendor support. I've seen some real abominations. The reason that JSF is so clean and flexible in comparison has less to do with the relative cleverness of the people involved and more to do with the fact that there were more people involved in more environments and the framework design and implementation wasn't secondary to a specific business app.

2. Generic database table view/edit. I wrote one of these, and one of these days, I'll add the last few features that it needs and open-source it. It has dynamic forms because it's not a business application, it's a database utility and therefore doesn't have a static pre-defined set of objects to work from.

3. Code generator. Been there/did that circa Y2K. Created an open-source tool called the EJBWizard that would introspect tables and apply a set of macro templates to generate compilable code. Originally, the code was EJB version 1 and the View definitions were JSPs. I later wrote templates for Struts and then JSF. Like I said, the concept transcends JSF.