1. Let's create a User class as the main object of our recipe:

public class User implements Serializable {

    private String name;
    private String email;

    public User(String name, String email) {
        this.name = name;
        this.email = email; 
    }
   
    //DON'T FORGET THE GETTERS AND SETTERS
    //THIS RECIPE WON'T WORK WITHOUT THEM
}

2. Now, we create a UserBean class to manage our UI:

@Named
@ViewScoped
public class UserBean implements Serializable {

    private User user;
    
    public UserBean(){
        user = new User("Elder Moraes", "[email protected]");
    }

    public void userAction(){
        FacesContext.getCurrentInstance().addMessage(null, 
                new FacesMessage("Name|Password welformed"));
    }

    //DON'T FORGET THE GETTERS AND SETTERS
    //THIS RECIPE WON'T WORK WITHOUT THEM
}

3. Now, we implement the Converter interface with a User parameter:

@FacesConverter("userConverter")
public class UserConverter implements Converter<User> {

    @Override
    public String getAsString(FacesContext fc, UIComponent uic, 
    User user) {
        return user.getName() + "|" + user.getEmail();
    }

    @Override
    public User getAsObject(FacesContext fc, UIComponent uic, 
    String string) {
        return new User(string.substring(0, string.indexOf("|")), 
        string.substring(string.indexOf("|") + 1));
    }

}

4. Now, we implement the Validator interface with a User parameter:

@FacesValidator("userValidator")
public class UserValidator implements Validator<User> {

    @Override
    public void validate(FacesContext fc, UIComponent uic, 
    User user) 
    throws ValidatorException {
        if(!user.getEmail().contains("@")){
            throw new ValidatorException(new FacesMessage(null, 
                                         "Malformed e-mail"));
        }
    }
}

5. And then we create our UI using all of them:

<h:body>
    <h:form>
        <h:panelGrid columns="3">
            <h:outputLabel value="Name|E-mail:" 
            for="userNameEmail"/>
            <h:inputText id="userNameEmail" 
            value="#{userBean.user}" 
            converter="userConverter" validator="userValidator"/> 
            <h:message for="userNameEmail"/>
        </h:panelGrid>
        <h:commandButton value="Validate" 
        action="#{userBean.userAction()}"/>
    </h:form> 
</h:body>

Don't forget to run it in a Java EE 8 server.