Disable a Vaadin Binding

Question

I have a component (e.g. a TextField) that will be shown depending on some other selection, a radio button for example, and when it is hidden I don't want the bind on this field to be applied, so

In some place:

Binder binder = new Binder<SomeDTO>(SomeDTO.class);
TextField conditionalComponet = TextField("A conditional component: ");
binder.bind(conditionalComponet, "propertyX");

and in some other place:

SomeDTO someDTO = new SomeDTO;
binder.writeBean(someDTO); //Here propertyX shouldn't be filled, i.e. bind should 
                       //not be applied, to propertyX of SomeDTO if the 
                       //conditionalComponet is hidden.

I wouldn't like to remove the component from layout since putting it in the same position will be a problem. I tried to setVisible(false), setEnabled(false) and setReadOnly(true), but none prevent the binding to be applied. Is there a simple way of doing that?

I am using Vaadin 8.

Answer 1

As far as I know there's no direct way to prevent a value from being set to a field by the binder, once it's bound. Nonetheless, you can work around this limitation(?!) easily, by using the bind(HasValue<FIELDVALUE> field, ValueProvider<BEAN,FIELDVALUE> getter, Setter<BEAN,FIELDVALUE> setter) method variant.

For a sample you can check the code below. Please note that it has just the basics parts to show the effect, so it does not have all the bells-and-whistles such as disabling or resetting the employment-date field with the check-box:

import com.vaadin.data.Binder;
import com.vaadin.data.ValidationException;
import com.vaadin.ui.*;

import java.io.Serializable;
import java.time.LocalDate;

public class DisableBindingForField extends VerticalLayout {
    private final Person person = new Person("Dark Vaper");
    private final TextField name = new TextField("Name:");
    private final CheckBox isEmployed = new CheckBox("Is employed:");
    private final DateField dateOfEmployment = new DateField("Date of employment:");
    private final Binder<Person> binder = new Binder<>(Person.class);
    private final Button button = new Button("Save");

    public DisableBindingForField() {
        // manually bind the custom field separately (https://vaadin.com/docs/-/part/framework/datamodel/datamodel-forms.html - scroll to the end)
        binder.bind(dateOfEmployment, person -> person.dateOfEmployment, (person, dateOfEmployment) ->
                // if the check-box is checked then populate the pojo with the value, otherwise reset the pojo value to null
                person.setDateOfEmployment((isEmployed.getValue()) ? dateOfEmployment : null)
        );

        // automatically bind the rest of the fields
        binder.bindInstanceFields(this);

        // initial reading of the bean
        binder.readBean(person);

        // add components to the user interface
        addComponents(name, isEmployed, dateOfEmployment, button);

        // simulate a "save button"
        button.addClickListener(event -> {
            try {
                binder.writeBean(person);
                Notification.show(person.toString());
            } catch (ValidationException e) {
                e.printStackTrace();
            }
        });
    }

    // basic pojo for binding
    public class Person implements Serializable {

        private String name;
        private Boolean isEmployed;
        private LocalDate dateOfEmployment;

        public Person(final String name) {
            this.name = name;
        }

        public String getName() {
            return name;
        }

        public void setName(final String name) {
            this.name = name;
        }

        public boolean isEmployed() {
            return isEmployed;
        }

        public void setEmployed(boolean employed) {
            isEmployed = employed;
        }

        public LocalDate getDateOfEmployment() {
            return dateOfEmployment;
        }

        public void setDateOfEmployment(LocalDate dateOfEmployment) {
            this.dateOfEmployment = dateOfEmployment;
        }

        @Override
        public String toString() {
            return "Person{" +
                    "name='" + name + '\'' +
                    ", isEmployed=" + isEmployed +
                    ", dateOfEmployment=" + dateOfEmployment +
                    '}';
        }
    }
}

Result:

P.S.: Alternative fluent-builder style:

binder.forField(dateOfEmployment)
      .bind(person -> person.dateOfEmployment, (person, dateOfEmployment) ->
          // if the check-box is checked then populate the pojo with the value, otherwise reset the pojo value to null
          person.setDateOfEmployment((isEmployed.getValue()) ? dateOfEmployment : null)
      );