Is it possible to update non-JSF components (plain HTML) with JSF ajax?

Is it possible to update parts of my page that are not JSF components?

For example, can I update a plain HTML <div> or do I need to wrap that in a JSF component?

Is it possible to update parts of my page that are not JSF components?

No. The to-be-updated component has to be available by UIViewRoot#findComponent(), so that JSF can find them, invoke encodeAll() on it, capture the generated HTML output and pass back it in the ajax response so that JavaScript can update the HTML DOM tree with it. Plain HTML elements are not represented as real UIComponent instances in the JSF component tree, so JSF already cannot locate them in first place.

For example, can I update a plain HTML <div> or do I need to wrap that in a JSF component?

You need to wrap it in a JSF component like <h:panelGroup>. You can however just use <h:panelGroup layout="block"> to represent a real <div> in JSF. This way you don't need to wrap the <div> in another JSF component.

<h:panelGroup layout="block" id="foo">
    ...
</h:panelGroup>

Since JSF 2.2 you can use new passthrough elements feature with jsf:id attribute to declare HTML(5) elements as JSF components.

<... xmlns:jsf="http://xmlns.jcp.org/jsf">

<div jsf:id="foo">
    ...
</div>

<main jsf:id="bar">
    ...
</main>

<section jsf:id="baz">
    ...
</section>

They will render their output as-is, but under the covers be a concrete UIPanel instance.

There's however one corner case in case of composite components. You can use the following approach to have a HTML element which is updateable by ajax.

<cc:implementation>
    <span id="#{cc.clientId}">
        ...
    </span>
</cc:implementation>

The explanation that this approach works is because even though the composite component does not render itself to the HTML output, it is by itself available by UIViewRoot#findComponent().

See also:

• How to find out client ID of component for ajax update/render? Cannot find component with expression "foo" referenced from "bar"
• Why do I need to nest a component with rendered="#{some}" in another component when I want to ajax-update it?
• Rerendering composite component by ajax

It seems that you can't.

to update something wrap it up in a 'updateable' component (in primeaces p:outputpanel) and update that one.

Addition: in your special case you can refresh the children of the p:tree that way: JSF update primefaces tree children

(haha always wanted to talk to me in third person)