How to validate fields in vaadin made form

Question

I am making a Java project with vaadin. Right now I have a user registration form looking like that:

public class RegistrationComponent extends CustomComponent i         


        

Answer 1

Vaadin 8

Using Vaadin 8 com.vaadin.data.Binder easily you can validate your fields. See Binding Data to Forms in the manual.

Create a TextField and a binder to validate the text field.

public class MyPage extends VerticalLayout{
     TextField investorCode = new TextField();
     Binder beanBinder = new Binder();
     //Info : MyBean class contains getter and setter to store values of textField.

     public MyPage (){
         investorCode.addValueChangeListener(e->valueChange(e));
         addComponent(investorCode);
         bindToBean();
     }

     private void bindToBean() {
         beanBinder.forField(investorCode)
         .asRequired("Field cannot be empty")
         .withValidator(investorCode -> investorCode.length() > 0,"Code shold be atleast 1 character long").bind(MyBean::getInvestorCode,MyBean::setInvestorCode);
     }

     //rest of the code .....
     private void valueChange(ValueChangeEvent e) {
         beanBinder.validate();
     }
}

Call validate() from binder will invoke the validation action.

beanBinder.validate(); 

to validate the filed. You can call this from anywhere in the page. I used to call this on value change or on a button click.