JSF Form Validation Using Ajax getting stuck

Question

I have two fields on a form that are cross validated. Initially the user see this:

<p:inputText size="5" 
  value="#{bean.maximum_hole_diameter}">
  <f:validator validatorId="doubleNotLessThanSecondDouble" />
  <f:attribute name="secondDouble" 
    value="#{bean.minimum_hole_diameter}" />
  <p:ajax event="change" update="@this" />
</p:inputText>

<p:inputText size="5" 
  value="#{bean.minimum_hole_diameter}">
  <f:validator validatorId="doubleNotGreaterThanSecondDouble" />
  <f:attribute name="secondDouble"
    value="#{bean.maximum_hole_diameter}" />
  <p:ajax event="change" update="@this" />
</p:inputText>

Everything works as expected IF the user enters a positive value for the maximum first and then a lesser value for the minimum.

If they enter the minimum first that gets flagged as invalid:

So far so good - 2 is larger than 0.0. Intuitively, the user would then put in a maximum hole diameter, which is larger than the minimum. But the form get's stuck. The minimum is still invalid because technically in the model it is still 0.0. Ajax never stored the value 2 in the model but the browser still shows the value 2. How can I get the 2 to get revalidated and stored in my bean??

I could do a update="@form" to clear the 2 value back to zero but this would frustrate the user. And if the user retypes 2, the form doesn't get submitted, because the it hasn't "changed". The user has to change to another number then go back to 2. Doing "onblur" has its issues too.

How can I get the value 2 to get resubmitted and revalidated when the user enters the 3?

Answer 1

There are a couple of problems here:

1. You're in <f:attribute> passing the model value to the validator instead of the component value. The updated model value is not necessarily available during Validations phase, which runs before Update Model Values phase. It will only work if the input field referencing this model value was successfully processed in a previous request. You'd better pass the physical component along which is referenced via binding and use UIInput#getValue() on it instead.

2. The <p:ajax> by default processes only the component it is nested in, as in process="@this". You really need to process the other component too in order to have the right value in the validator.

3. You're not updating the other input when changing one input. So the other input will never be able to remove the error highlight when validation on it actually succeeds.

All in all, this should do it:

<p:inputText id="max" binding="#{max}" ...>
    <f:validator validatorId="doubleNotLessThanSecondDouble" />
    <f:attribute name="secondComponent" value="#{min}" />
    <p:ajax process="@this min" update="@this min" />
</p:inputText>

<p:inputText id="min" binding="#{min}" ...>
    <f:validator validatorId="doubleNotGreaterThanSecondDouble" />
    <f:attribute name="secondComponent" value="#{max}" />
    <p:ajax process="@this max" update="@this max" />
</p:inputText>

With below logic in those validators:

double firstDouble = (double) value;
UIInput secondComponent = (UIInput) component.getAttributes().get("secondComponent");
double secondDouble = (double) secondComponent.getValue();
// ...

See also:

• JSF doesn't support cross-field validation, is there a workaround?
• Understanding PrimeFaces process/update and JSF f:ajax execute/render attributes
• What is component binding in JSF? When it is preferred to be used?

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If you happen to use JSF utility library OmniFaces, or are open to using it, then it's good to know that this requirement is also covered by <o:validateOrder> as below (without need for any custom validator):

<h:panelGroup id="diameter">
    <p:inputText id="max" ...>
        <p:ajax process="diameter" update="diameter" />
    </p:inputText>

    <p:inputText id="min" ...>
        <p:ajax process="diameter" update="diameter" />
    </p:inputText>

    <o:validateOrder type="gt" components="max min" />
</h:panelGroup>

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Unrelated to the concrete problem, you'd better use BigDecimal instead of double if accuracy is that important.