Using Bean Validation to validate input

Before you get started with Bean Validation you need to download a Bean Validation implementation and add it to your project. You can find one for instance at https://bval.apache.org/downloads.html. Just add the jars from the lib folder to your project.

Bean Validation works as a normal validator. If you have a bean with Bean Validation annotations, such as:

public class Person {

  @Size(min = 5, max = 50)
  private String name;

  @Min(0)
  @Max(100)
  private int age;
  // + constructor + setters + getters
}

You can create a field for the name field as you always would:

Person person = new Person("John", 26);
TextField firstName = new TextField("First name");

setContent(firstName);

and bind the field with a bean validation binder:

BeanValidationBinder<Person> binder = new BeanValidationBinder<>(Person.class);
binder.forField(firstName).bind("name");
binder.setBean(person);

Your firstName field is now automatically validated based on the annotations in your bean class. You can do the same thing for the age field and you won’t be able to set a value outside the valid 0-100 range.

A Bean Validation tutorial is available here: https://docs.oracle.com/javaee/6/tutorial/doc/gircz.html