- 

Available since OmniFaces 1.0

The <o:validator> is a taghandler that extends the standard <f:validator> tag family with support for deferred value expressions in all attributes. In other words, the validator attributes are not evaluated anymore on a per view build time basis, but just on every access like as with UI components and bean properties. This has among others the advantage that they can be evaluated on a per-iteration basis inside an iterating component, and that they can be set on a custom validator without needing to explicitly register it in a tagfile.

Usage

When you specify for example the standard <f:validateLongRange> by validatorId="javax.faces.LongRange", then you'll be able to use all its attributes such as minimum and maximum as per its documentation, but then with the possibility to supply deferred value expressions.

<o:validator validatorId="javax.faces.LongRange" minimum="#{item.minimum}" maximum="#{item.maximum}" />

The validator ID of all standard JSF validators can be found in their javadocs. First go to the javadoc of the class of interest, then go to VALIDATOR_ID in its field summary and finally click the Constant Field Values link to see the value.

It is also possible to specify the validator message on a per-validator basis using the message attribute. Any "{0}" placeholder in the message will be substituted with the label of the referenced input component. Note that this attribute is ignored when the parent component has already validatorMessage specified.

<o:validator validatorId="javax.faces.LongRange" minimum="#{item.minimum}" maximum="#{item.maximum}"
    message="Please enter between #{item.minimum} and #{item.maximum} characters" />

JSF 2.3 compatibility

The <o:validator> is currently not compatible with validators which are managed via JSF 2.3's new managed=true attribute set on the FacesValidator annotation, at least not when using Mojarra. Internally, the converters are wrapped in another instance which doesn't have the needed setter methods specified. In order to get them to work with <o:validator>, the managed=true attribute needs to be removed, so that OmniFaces ValidatorManager will automatically manage them.

Demo

In the below first demo, it was the intent to use <f:validateLongRange> as follows:

 <f:validateLongRange minimum="#{question.minimum}" maximum="#{question.maximum}" />

But this fails hard as the minimum and maximum values are set during view build time instead of during processing the validation. The #{question} is not available during view build time and thus both minimum and maximum will default to 0 (for a background explanation, check this Stack Overflow answer). It works as intuitively expected with the <o:validator> as it allows a render time evaluation of attributes.

For another related use case, checkout the <o:converter> showcase page.

Further, the <o:validator> also allows setting the validation message on a per-validator basis by the message attribute. This is not possible with <f:validator> and the validatorMessage attribute of the parent input component applies to all validators. Note that the message attribute of <o:validator> has no effect when the validatorMessage attribute of the parent input component has already been set.

Demo

With f:validateLongRange in each row - fails!

Enter value between 1 and 9
Enter value between 5 and 10
Enter value between 3 and 7

With o:validator in each row - works!

Enter value between 1 and 9
Enter value between 5 and 10
Enter value between 3 and 7

Set validator message on a per-validator basis

Demo source code
<h3>With f:validateLongRange in each row - fails!</h3>
<h:form>
    <h:dataTable value="#{validatorBean.questions}" var="question">
        <h:column>
            Enter value between #{question.minimum} and #{question.maximum}
        </h:column>
        <h:column>
            <h:inputText id="input" value="#{question.answer}" required="true" requiredMessage="Fill out the value!">
                <f:validateLongRange minimum="#{question.minimum}" maximum="#{question.maximum}" />
            </h:inputText>
        </h:column>
        <h:column>
            <h:message for="input" />
        </h:column>
    </h:dataTable>
    <h:commandButton value="Submit">
        <f:ajax execute="@form" render="@form" />
    </h:commandButton>
    <h:outputText value="OK!" rendered="#{facesContext.postback and not facesContext.validationFailed}" />
</h:form>

<hr />

<h3>With o:validator in each row - works!</h3>
<h:form>
    <h:dataTable value="#{validatorBean.questions}" var="question">
        <h:column>
            Enter value between #{question.minimum} and #{question.maximum}
        </h:column>
        <h:column>
            <h:inputText id="input" value="#{question.answer}" required="true" requiredMessage="Fill out the value!">
                <o:validator validatorId="javax.faces.LongRange" minimum="#{question.minimum}" maximum="#{question.maximum}" message="Invalid value!" />
            </h:inputText>
        </h:column>
        <h:column>
            <h:message for="input" />
        </h:column>
    </h:dataTable>
    <h:commandButton value="Submit">
        <f:ajax execute="@form" render="@form" />
    </h:commandButton>
    <h:outputText value="OK!" rendered="#{facesContext.postback and not facesContext.validationFailed}" />
</h:form>

<hr />

<h3>Set validator message on a per-validator basis</h3>
<h:form>
    <h:messages />
    <h:dataTable binding="#{table}" value="#{validatorBean.entities}" var="entity">
        <h:column>
            <c:set var="label" value="Input #{table.rowIndex + 1}" />
            <o:outputLabel for="input" value="#{label}" />
        </h:column>
        <h:column>
            <h:inputText id="input" value="#{entity.value}" required="true" requiredMessage="#{label} is required">
                <o:validator validatorId="javax.faces.Length" minimum="5" message="{0} must be at least 5 chars" />
                <o:validator validatorId="javax.faces.RegularExpression" pattern="\\d+" message="{0} must contain digits only" /><!-- Fails in Apache EL (Tomcat/TomEE/etc), use \d+ instead. -->
            </h:inputText>
        </h:column>
    </h:dataTable>
    <h:commandButton value="Submit">
        <f:ajax execute="@form" render="@form" />
    </h:commandButton>
    <h:outputText value="OK!" rendered="#{facesContext.postback and not facesContext.validationFailed}" />
</h:form>
Documentation & Sources

VDL documentation

API documentation

Java source code