How to perform validation in JSF and how to create a custom validator in JSF

I want to perform validation in some of my input components, such as < H: inputtext > using some java bean methods Should I use < F: validator > or < F: validatebean > for this? Where can I read more about it?

Solution

You only need to implement the validator interface

@FacesValidator("myValidator")
public class MyValidator implements Validator {

    @Override
    public void validate(FacesContext context,UIComponent component,Object value) throws ValidatorException {
        // ...

        if (valueIsInvalid) {
            throw new ValidatorException(new FacesMessage("Value is invalid!"));
        }
    }

}

@Facesvalidator will register it with JSF using the verifier ID myvalidator so that you can reference it in any verifier attribute of < H: inputxxx > / < H: selectxxx > The components are as follows:

<h:inputText id="foo" value="#{bean.foo}" validator="myValidator" />
<h:message for="foo" />

You can also use < F: validator >, which is the only way to attach multiple validators to the same component:

<h:inputText id="foo" value="#{bean.foo}">
    <f:validator validatorId="myValidator" />
</h:inputText>
<h:message for="foo" />

Whenever the validatorexception is thrown by the validator, its message will be displayed in < H: Message > Associated with an input field

You can use < F: validator binding > to reference a specific validator instance somewhere within the El range, which in turn can be easily provided as a lambda:

<h:inputText id="foo" value="#{bean.foo}">
    <f:validator binding="#{bean.validator}" />
</h:inputText>
<h:message for="foo" />

public Validator getValidator() {
    return (context,component,value) -> {
        // ...

        if (valueIsInvalid) {
            throw new ValidatorException(new FacesMessage("Value is invalid!"));
        }
    };
}

To go further, you can use JSR 303 bean validation This validates the field against the comments As this will be a complete story, here are just some getting started links:

> Hibernate Validator – Getting started > JSF 2.0 tutorial – Finetuning validation

< F: validatebean > is only useful if you intend to disable JSR 303 bean validation Then put the input component (or even the whole form) in < F: validatebean disabled = "true" >

You can also see:

> JSF doesn’t support cross-field validation,is there a workaround? > How to perform JSF validation in actionListener or action method?