Rendering other form by ajax causes its view state to be lost, how do I add this back?

This is a known problem in the auto-included jsf.js library of JSF which handles ajax responses. See also JSF spec issue 790 which is fixed in the upcoming JSF 2.3. In the meanwhile, with JSF 2.0/2.1/2.2, you have to explicitly specify the ID of the other <h:form> inside the render attribtue to trigger proper addition of the view state.

<h:form>
    <h:commandLink action="#{my_fake_ajax_link}">
        <h:outputText value="Link" />
        <f:ajax render=":mydiv :mydivForm" />
    </h:commandLink>
</h:form>

<h:panelGroup layout="block" id="mydiv">
    <h:form id="mydivForm">
        <h:commandLink action="#{mybean.delete(0)}">
            <h:outputText value="Here" />
            <f:ajax render="@form" />
        </h:commandLink>
    </h:form>
</h:panelGroup>

No, this does not cause any overhead or markup duplication in the ajax response. Alternatively, use OmniFaces fixviewstate.js.

See also:

• Communication in JSF 2.0 - Ajax rendering of content which contains another form
• h:commandButton/h:commandLink does not work on first click, works only on second click