JSF converter causes validator(s) to be ignored

Question

Here\'s the field:

Answer 1

Conversion happens before validation. Converters will also be called when the value is null or empty. If you want to delegate the null value to the validators, then you need to design your converters that it just returns null when the supplied value is null or empty.

@Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
    if (value == null || value.trim().isEmpty()) {
        return null;
    }

    // ...
}

---

Unrelated to the concrete problem, your validator has a flaw. You should not extract the submitted value from the component. It's not the same value as returned by the converter. The right submitted and converted value is available as the 3rd method argument already.

@Override
public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
    if (value == null) {
        return; // This should normally not be hit when required="true" is set.
    }

    String phoneNumber = (String) value; // You need to cast it to the same type as returned by Converter, if any.

    if (!phoneNumber.matches("04\\d{8}")) {
        throw new ValidatorException(new FacesMessage(FacesMessage.SEVERITY_ERROR, "Please enter a valid mobile phone number.", null));
    }
}

Answer 2

After reading BalusC's comment I am updating this post again.

I created a small demo application and to see the phases and when the conversion and validation occur.

View:

<h:form>
    <h:inputText value="#{demoBean.field}">
        <f:converter converterId="demoConverter"/>
        <f:validator validatorId="demoValidator"/>
    </h:inputText>
    <h:commandButton value="Submit" action="#{demoBean.demoAxn()}"/>
</h:form>

Managed bean:

@ManagedBean
@SessionScoped
public class DemoBean implements Serializable {
    private String field;

    public DemoBean() {
        System.out.println(Thread.currentThread().getStackTrace()[1]);
    }

    public String getField() {
        System.out.println(Thread.currentThread().getStackTrace()[1]);
        return field;
    }

    public void setField(String field) {
        System.out.println(Thread.currentThread().getStackTrace()[1]);
        this.field = field;
    }

    public String demoAxn() {
        System.out.println(Thread.currentThread().getStackTrace()[1]);
        return null;
    }
}

Converter:

@FacesConverter(value="demoConverter")
public class DemoConverter implements Converter {

    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        System.out.println(Thread.currentThread().getStackTrace()[1]);            
        return value;
    }

    @Override
    public String getAsString(FacesContext context, UIComponent component, Object value) {
        System.out.println(Thread.currentThread().getStackTrace()[1]);
        return (String) value;
    }    
}

Validator:

@FacesValidator(value="demoValidator")
public class DemoValidator implements Validator {

    @Override
    public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
        System.out.println(Thread.currentThread().getStackTrace()[1]);
    }

}

Phase listener:

public class DemoPhaseListener implements PhaseListener {
    @Override
    public void afterPhase(PhaseEvent event) {
        System.out.println(Thread.currentThread().getStackTrace()[1]);
        System.out.println("PhaseId: " + event.getPhaseId() + "  ===============================\n\n");        
    }

    @Override
    public void beforePhase(PhaseEvent event) {
        System.out.println("\n\nPhaseId: " + event.getPhaseId() + "  ===============================");
        System.out.println(Thread.currentThread().getStackTrace()[1]);        
    }

    @Override
    public PhaseId getPhaseId() {
        return PhaseId.ANY_PHASE;
    }    
}

Registered the phase listener:

<lifecycle>
    <phase-listener>pkg.DemoPhaseListener</phase-listener>
</lifecycle>

With that setting when the "Submit" button is clicked, the output is:

INFO: PhaseId: RESTORE_VIEW 1  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: RESTORE_VIEW 1  ===============================

INFO: PhaseId: APPLY_REQUEST_VALUES 2  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: APPLY_REQUEST_VALUES 2  ===============================

INFO: PhaseId: PROCESS_VALIDATIONS 3  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoConverter.getAsObject(DemoConverter.java:13)
INFO: pkg.DemoValidator.validate(DemoValidator.java:14)
INFO: pkg.DemoBean.getField(DemoBean.java:17)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: PROCESS_VALIDATIONS 3  ===============================

INFO: PhaseId: UPDATE_MODEL_VALUES 4  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoBean.setField(DemoBean.java:22)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: UPDATE_MODEL_VALUES 4  ===============================

INFO: PhaseId: INVOKE_APPLICATION 5  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoBean.demoAxn(DemoBean.java:27)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: INVOKE_APPLICATION 5  ===============================

INFO: PhaseId: RENDER_RESPONSE 6  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoBean.getField(DemoBean.java:17)
INFO: pkg.DemoConverter.getAsString(DemoConverter.java:20)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: RENDER_RESPONSE 6  ===============================

But when make change to throw a NPE in the converter as follows:

@Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
    System.out.println(Thread.currentThread().getStackTrace()[1]);            
    throw new NullPointerException();
}

the output is:

INFO: PhaseId: RESTORE_VIEW 1  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: RESTORE_VIEW 1  ===============================

INFO: PhaseId: APPLY_REQUEST_VALUES 2  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: APPLY_REQUEST_VALUES 2  ===============================

INFO: PhaseId: PROCESS_VALIDATIONS 3  ===============================
INFO: pkg.DemoPhaseListener.beforePhase(DemoPhaseListener.java:17)
INFO: pkg.DemoConverter.getAsObject(DemoConverter.java:13)
INFO: pkg.DemoPhaseListener.afterPhase(DemoPhaseListener.java:10)
INFO: PhaseId: PROCESS_VALIDATIONS 3  ===============================

INFO: pkg.DemoBean.getField(DemoBean.java:17)

But the stacktrace is displayed on the resulting view.