vaadin-framework/documentation/articles/UsingBeanValidationToValidateInput.asciidoc

---
title: Using Bean Validation To Validate Input
order: 45
layout: page
---

[[using-bean-validation-to-validate-input]]
= 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 http://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:

[source,java]
....
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:

[source,java]
....
Person person = new Person("John", 26);
TextField firstName = new TextField("First name");

setContent(firstName);
....

and bind the field with a bean validation binder:

[source,java]
....
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:
http://docs.oracle.com/javaee/6/tutorial/doc/gircz.html