bean validation support

Bean Validation support

Easy Random can introspect fields annotated with Bean Validation API annotations and generate random values according to declared validation constraints. Let's see an example, here is a Person class:

public class Person {

    private String name;

    @javax.validation.constraints.Size(min = 5, max = 10)
    private List<String> nickNames;

    @javax.validation.constraints.Past
    private Date birthDate;

    // constructors, getters and setters omitted
}

If you populate a Person bean using Easy Random, the generated value for nickNames will be a list containing a random number of Strings in the [5, 10] range and the birthDate field will be a random date in the past. This feature allows you to generate valid random data according to constraints already defined on your beans. In order to activate Bean Validation support, you need to add the easy-random-bean-validation dependency to your project:

<dependency>
   <groupId>org.jeasy</groupId>
   <artifactId>easy-random-bean-validation</artifactId>
   <version>${latest.version}</version>
</dependency>

Bean Validation contraint parameters precedence

Bean validation constraint parameters will take precedence over global parameters, except for custom randomizers and registries. This means that, in the previous example:

• nickNames will still be populated with a random number of elements in the [5, 10] range, even if the collectionSizeRange is set to [1, 4] for example.
• if a custom Date randomizer generating dates in the future is registered for the field birthdate, then this field will be randomized with a date in the future and not in the past anymore as declared by the constraint.

The following example shows the expected behaviour:

@Test
void testParametersPrecedence() {
    // given
    class Person {
        @Size(min = 5, max = 10)
        private List<String> names;
        @javax.validation.constraints.Past
        private LocalDate birthDate;
    }
    LocalDate today = LocalDate.now();
    EasyRandomParameters parameters = new EasyRandomParameters().collectionSizeRange(1, 4)
            .randomize(FieldPredicates.named("birthDate").and(FieldPredicates.inClass(Person.class)),
                    new LocalDateRangeRandomizer(today, today.plusYears(10)));
    EasyRandom easyRandom = new EasyRandom(parameters);
    
    // when
    Person person = easyRandom.nextObject(Person.class);
    
    // then
    assertThat(person.names.size()).isBetween(5, 10); // Bean Validation constraint parameters take precedence
    assertThat(person.birthDate).isAfterOrEqualTo(today); // custom randomizers take precedence
}

Supported annotations

Easy Random can generate random valid data for all Bean Validation API annotations except @Digits. There is no plan to support this annotation in a future release, you should use a custom randomizer for fields annotated with @Digits.