A few questions reagarding UI components state and phases

0
votes

Having gone through these excellent posts:

Why JSF saves the state of UI components on server?

Why does JSF save component tree state?

and midway the JavaEE6 tutorial I still have the following questions:

  1. When I am developing a custom UI component whose values (styleClass, value, etc) are either defined statically(in the xhtml) or set via a bean, do I need to explicitly save/restore state in the extended component as well?
  2. Is it correct to say that the scope of the UI components is view scoped?
  3. How is the view identified behaviour? (If I navigate away from a view, the view gets rebuild the next time around. But if I open another tab, it is restored - at least the bean!)
  4. When I am executing an Ajax call, I would expect that 'execute' part of the UI component would be restored&processed and the 'rendered' part would be restored&updated. After running into some problems with UI:repeat, it is not clear to which extend the component tree is to be restored and if is possible to partially edit. As an example (I am not sure that it works like this): I define a UI:repeat that iterates over some values and creates some Ajax commandlinks. Whenever I call the command, it will restore the whole ui:repeat regardless of the Ajax scope (execute/render) that I have defined. So it will re-render the whole ui:repeat. Furthermore, I don't understand how it could ever -not- restore the ui:repeat as due to being a namingcontainer it will edit the id of my newly added component.
  5. How can I define a build-time component (vs render-time) and why would I want to do this? (It seems that build time components are troublesome when mixed with rendertime, so why have both)

Thanks

1
jsfjsf-2
I understand the personal ease of asking many questions at once, but in the future please ask one question per question :) This makes it easier to flesh out answers or point out a duplicate question and inherently also to others to search and find a specific question. – BalusC
I just asked many questions as I found that they would end up to a more complete answer like the link I quoted which was very useful. Will stick with single questions in the future ;) - thanks – Ioannis Deligiannis

1 Answers

7
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When I am developing a custom UI component whose values (styleClass, value, etc) are either defined statically(in the xhtml) or set via a bean, do I need to explicitly save/restore state in the extended component as well?

Yes. You normally use StateHelper for this.

See also:

Is it correct to say that the scope of the UI components is view scoped?

Absolutely not. UI component instances are request scoped. Only anything which is stored via StateHelper is in essence view scoped (and restored into newly created component instances during "restore view" phase).

See also:

How is the view identified behaviour? (If I navigate away from a view, the view gets rebuild the next time around. But if I open another tab, it is restored - at least the bean!)

It's likely requested from browser cache. Try submitting a form therein. The chance is big that you get a ViewExpiredException. You need to tell the browser to not cache dynamic pages. Putting a breakpoint on bean's constructor would also confirm that it's never been invoked.

See also:

When I am executing an Ajax call, I would expect that 'execute' part of the UI component would be restored&processed and the 'rendered' part would be restored&updated.

This is not true as to restore part. The "whole" view state is restored. Note that the view state does since JSF 2.0 not necessarily represent the entire component tree. You've found the explanation/answer to that already in the two links mentioned in your question.

How can I define a build-time component (vs render-time) and why would I want to do this? (It seems that build time components are troublesome when mixed with rendertime, so why have both)

This is called a "tag handler". I.e. just extend from TagHandler instead of UIComponent and implement according its contract. Tag handlers are useful if the sole goal is to build the view (the JSF component tree). They do not appear in the JSF component tree. As to when to create a custom component or a custom tag handler, check the "components" and "taghandlers" sections of OmniFaces showcase, it may give some new insights as to real world use cases of those things.

See also: