Form submit in conditionally rendered component is not processed - ajax

Question

I have a custom tagfile with a form:
<h:form>
<h:commandButton value="click">
<f:ajax event="click" listener="#{bean[method]}" />
</h:commandButton>
</h:form>
I'm conditionally rendering it by ajax as below:
<h:panelGroup id="test">
<h:form>
<h:commandButton value="click">
<f:ajax event="click" listener="#{backingTest.updateFlag}" render=":test"/>
</h:commandButton>
</h:form>
<h:panelGroup rendered="#{backingTest.flag}">
<my:customtag bean="#{backingTest}" method="printMessage"/>
</h:panelGroup>
</h:panelGroup>
This is the associated backing bean:
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
#ManagedBean
#RequestScoped
public class BackingTest {
private boolean flag = false;
public void printMessage() {
System.out.println("hello");
}
public void updateFlag() {
flag = true;
}
public boolean getFlag() {
return flag;
}
}
When I click the first command button, then the updateFlag() method is properly invoked and the second command button is properly shown. But when I then click the second command button, it never hits the printMessage() method. In the web browser's JS console and HTTP traffic monitor I can see that the click event is successfully fired and that the XHR POST request is successfully being sent.
If I remove the rendered attribute, then everything works as expected.
How is this caused and how can I solve it? I'm using Mojarra 2.1.25.

Answer 1

Your concrete problem is caused by 2 facts:
When JSF needs to decode a form submit action or a submitted input value, then it also checks if the component is rendered or not (as safeguard against hacked/tampered requests).
Request scoped beans are recreated on every HTTP request (an ajax request counts also as one request!).
In your specific case, the rendered condition has evaluated false while JSF needs to decode the form submit action and therefore the non-rendered input/command components are never processed.
Putting the bean in view scope should fix it. Below example assumes JSF 2.x.
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
#ManagedBean
#ViewScoped
And below example assumes JSF 2.2+ with CDI:
import javax.inject.Named;
import javax.faces.view.ViewScoped;
#Named
#ViewScoped
Or, if the techncial requirement is to keep the bean in request scope, then carry around the condition behind rendered attribute in a <o:inputHidden>. Adjust your snippet to include it in the <h:form>.
<o:inputHidden value="#{backingTest.flag}" />
See also:
commandButton/commandLink/ajax action/listener method not invoked or input value not set/updated - point 6
How to choose the right bean scope?