JSR-303 Bean Validation. Emmanuel Bernard Doer JBoss, a Division of Red Hat

Transcription

1 JSR-303 Bean Validation Emmanuel Bernard Doer JBoss, a Division of Red Hat emmanuel@hibernate.org

2 Emmanuel Bernard Hibernate Search in Action blog.emmanuelbernard.com twitter.com/emmanuelbernard

3 Help the planet, write less code Express data constraints once and for all across all the layers of your application

4 Constraints Constraint restriction on a bean, field or property not null, between 10 and 45, valid ... How is that useful give feedback to the user ensure that a service will behave correctly define service range of usability avoid adding crap to the database unless you like fixing the data manually

5 Constraints in the Java Ecosystem Where should they be applied Java Client Side Presentation Layer Business Layer Data Access Layer Database How many model do I have? 1

6 So what is the problem? Duplication multiple declarations of the same constraint code duplication risk of inconsistency Multiple runtime checking not all constraints can be expressed by all engines slightly different semantic?

7 What is the solution? Uniform way to express a constraint everybody speaks the same language based on the domain model (JavaBeans) Standard way to validate constraints one runtime engine same validation implementations shared Bridge for constraints out of Java land API to access the constraint repository

8 Solutions? JavaDoc Validation method in the object XML!

9 Demo

10 Expressing constraint: annotations Using annotations extends type system next to the class definition public class message="longer than {max} characters") private String street1; private String street2;... }

11 How to express a constraint Annotation based annotate the target (bean, field, getter) Annotation elements message groups and custom parameters

12 Validating an object graph public class message="longer than {max} characters") private private Country country; } public class private String name;... }

13 Groups Subset of constraints Partial validation screen of a wizard UI Constraints applied in a given use case Order constraint validations which depends on other validations when a constraint is resource/time intensive

14 interface Billable {} interface BuyInOneClick extends Billable, Default {} class User Address getdefaultcreditcard() {...} //Default group String getusername() Heavy.class}) interface Complete {}

15 Create our own constraint Annotation with expressive name list of ConstraintValidators Composition Advance error reporting if needed

16 How to define a new SizeValidatorForCollections.class), SizeValidatorForString.class } ) Size { String message() default "{validation.size}"; Class[] groups() default {}; int min() default 0; int max() default Integer.MAX_VALUE; }

17 public class SizeValidatorForString implements ConstraintValidator<Size, String> { public void initialize(size annotation) {} } public boolean isvalid(string value, ConstraintValidatorContext context) {}

18 Composition Reuse constraints expose FrenchZipCode { String message() default "{validation.length}"; Class[] groups() default {}; }

19 @ReportAsViolationFromCompositeConstraint FrenchZipCode { String message() default "{validation.length}"; Class[] groups() parameter= min parameter= max ) } int size() default 5; parameter= message ) } String sizemessage() default not right size ;

20 20 Built-in Constraints But you can write your own! In for

21 Usage Validation triggered by other frameworks JPA on entity change JSF validate properties EL bind a component to a bean Use appropriate Locale for MessageInterpolator Any framework in need for validation

22 Outside Java boundaries DDL generation, tools, JavaScript generators Metadata API Constraint Composition elementary bricks understood

23 Explicit call Validate a bean ValidatorFactory vf = Validation.buildDefaultValidatorFactory(); Validator vf.getvalidator(); [...] Set<ConstraintViolation<User>> errors = validator.validate(user, BuyInOneClick.class); Java EE injection Returns invalid constraints invalid value / invalid root bean internationalized message path to the failing property

24 Ultimate goal Common constraint declaration no duplication close to the code, close to the model Reused layers application frameworks JSRs Declarative validation Extensible

25 Hibernate Validator 4 Reference Implementation ASL 2.0 Road Map

26 Questions

27 27 For More Information JCP.org Search for Bean Validation Hibernate Validator