<f:ajax> contains an unknown id :someid when used in <ui:repeat>

My code snippet:

<ui:repeat var="o">
   <h:panelGroup id="someid">
      <ui:repeat>
         // HTML
      </ui:repeat>
   </h:panelGroup>

   <div>
      <h:form>
          <h:commandButton action="#{o.doSomething}">
            开发者_StackOverflow  <f:ajax event="action" render=":someid" />
          </h:commandButton>
      <h:form>
   </div>
</ui:repeat>

Why didn't <f:ajax> find someid?

That's not possible. The <ui:repeat> prepends the client ID with its own ID and an index. All those panelgroups get IDs like j_id1:0:someid, j_id1:1:someid, j_id1:2:someid, etc. The following is supposed to work in your particular construct:

<f:ajax render=":#{component.parent.parent.clientId}:someid" />

This will prepend the <ui:repeat>'s current client ID dynamically. It however only works when you're using with MyFaces instead of Mojarra. The <ui:repeat> is broken in many ways in Mojarra. They have scheduled many fixes for 2.2.

An alternative is to group them in a common NamingContainer component like <h:form>, so that you can use a relative ID.

<ui:repeat var="o">
    <h:form>
        <h:panelGroup id="someid">
            <ui:repeat>
                // HTML
            </ui:repeat>
        </h:panelGroup>

        <div>
            <h:commandButton action="#{o.doSomething}">
                <f:ajax event="action" render="someid" />
            </h:commandButton>
        </div>
    <h:form>
</ui:repeat>