JSF same ID on rendered

Question

Let's say I am using rendered as basically a case statement. I have a label and message for an input field, but I want the field itself to change depending on the case. As such:

<p:inputText id="foo" value="#{myBean.params[paramKey]}" 
   rendered="#{paramIsInput}" />
<p:calendar  id="foo" value="#{myBean.params[paramKey]}" 
   rendered="#{paramIsCalendar}" />

If I do that then I get the following error: java.lang.IllegalStateException: Component ID j_idt64:foo has already been found in the view.

As a workaround I created lots of labels/messages for each param type and changed their ids. But this brings my question. If only one component with an id is actually rendered, why would it matter that I have multiple defined in my jsf file? Is there a way to keep them with all the same ID?

Consider the use case where `paramIsInput` and `paramIsCalendar` both are true... — Bharat Sinha, Aug 28 '12 at 17:13
Change the id of your `` or your ``. Even if the control is not rendered, they can't have the same id. — Luiggi Mendoza, Aug 28 '12 at 17:17
@SiB I actually do a check of paramType == on each so they can only have 1 true. That's not the issue — Daniel Moses, Aug 28 '12 at 17:28
@DMoses You know that... this can't be used for decision making while writing the specifications :) — Bharat Sinha, Aug 28 '12 at 17:35

score 10 · Answer 1 · edited Jun 20 '20 at 09:12

10

JSF component IDs are supposed to be unique during view build time already, not during view render time only. This way you effectively end up with two JSF components with the same ID which is indeed invalid. You'd like to effectively end up with one JSF component with the desired ID in the JSF component tree after view build time.

You can achieve this by populating the component during the view build time instead of generating its HTML output conditionally during the view render time. You can use the JSTL <c:if> tag for this.

<c:if test="#{paramIsInput}">
    <p:inputText id="foo" value="#{myBean.params[paramKey]}" />
</c:if>
<c:if test="#{paramIsCalendar}">
    <p:calendar id="foo" value="#{myBean.params[paramKey]}" />
</c:if>

This has however caveats: the <c:if test> condition can't depend on a variable which is only known during JSF render time. So it has not to depend on var of a JSF iterating component, or to be a property of a view scoped bean, etc.

Good information, but the conditional is on a view scoped bean as I have a select listiner that changes the input fields. – Daniel Moses Aug 28 '12 at 17:33
Then you'd have to let the condition depend on a request parameter instead of a view scoped bean property. E.g. `` would only evaluate true when `` is submitted with the option value "someValue". – BalusC Aug 28 '12 at 17:35
Thanks again for the information, I read the JSTL in JSF2. My whole question was inside a repeater, so that makes the jstl solution not-viable, but I learned a lot from your answer. – Daniel Moses Aug 28 '12 at 18:13

score 4 · Accepted Answer · edited Mar 30 '16 at 10:16

4

If only one component with an id is actually rendered, why would it matter that I have multiple defined in my jsf file?

How would JSF know that only one component will be rendered? You are using EL in rendered and both can evaluate to true. Here is the documentation which says you can't have duplicate ids inside a naming container.

The specified identifier must be unique among all the components (including facets) that are descendents of the nearest ancestor UIComponent that is a NamingContainer, or within the scope of the entire component tree if there is no such ancestor that is a NamingContainer.

-

Is there a way to keep them with all the same ID?

In case you still want to have same ids on more than one components you need to separate the naming container.

You can use PanelGrid as a naming container.

edited Mar 30 '16 at 10:16

Gawron

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answered Aug 28 '12 at 17:18

Bharat Sinha

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Thanks. I guess what I was hoping for was a true switch statement that would be recognized as such so JSF knew that they couldn't be duplicates. The namingcontainer makes sense, but as I wanted the message and label to match on the same id, that won't work. I guess I'll keep it with the multiple labels/messages and different IDs that I have. – Daniel Moses Aug 28 '12 at 17:31
PanelGrid is not a naming container – kaiser Oct 30 '17 at 20:02

JSF same ID on rendered

2 Answers2

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