JSF h：inputFile自定义验证器未调用

Question

I'm building a custom valdiator to do some validations over an uploaded image so I did the following :

<h:form styleClass="form" role="form" prependId="false" enctype="multipart/form-data">  
          <h:inputFile  styleClass="form-control"  id="slideImage"> 
                 <f:validator validatorId="NewImageValidator"/>
          </h:inputFile>
// Rest of form data & components
</h:form>

NewImageValidator.java

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

    @Override
    public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
        System.out.println("NewImageValidator");

    }
}

The issue is that the validator is never called (NewImageValidator is never printed on output) inside the h:inputFile tried calling the validator inside an h:inputText and it worked just fine So what is the wrong with h:inputFile here

Thanks in advance

Answer 1

<h:inputFile  styleClass="form-control"  id="slideImage"> 
    <f:validator validatorId="NewImageValidator"/>
</h:inputFile>

First, you are- not using a value on the h:inputFile , hence your file will not be submitted into any BakingBean Property and the value passed to the converter will always be null . That's not true actually. The validator will still pickup the right value, but ofc. if you want continue to use the file, you should store it in your backing bean.

Second, your form is missing a submit button. If you have a look at the JSF LifeCycle, the validation is invoked, after the values of the components have been evaluated (after submitting a form, not while the user fills out data, ie is picking a file)

If you want to execute the validation right away, there is no way around (partial)-submitting the form and transfer the file to the server. Depending on the size this might be a bad approach.

Bot for that purpose you can use f:ajax :

<h:form styleClass="form" role="form" prependId="false" enctype="multipart/form-data">  
    <h:inputFile value="#{myBean.uploadedFile}" styleClass="form-control"  id="slideImage"> 
        <f:validator validatorId="NewImageValidator"/>
        <f:ajax event="change" execute="slideImage" /> 
    </h:inputFile>
</h:form>

but i would prefer to only transfer files the user decides to submit (using a regular submit button). He might re-pick several files, and you don't need to upload them all as the user changes his mind.

I think there is no client-side validation of files, because your browser would not allow any client-side script to access an unsubmitted file on the filesystem.