This document discusses integrating Apache Bean Validation with Google Guice. It describes how to bootstrap Bean Validation using Guice, obtain ConstraintValidator instances via Guice injection, require injection of javax.validation components, and intercept methods to validate arguments. Integrating the two allows for dependency injection with Bean Validation and easy validation of method arguments using annotations.

1. JSRs 303 and 330 in Action
Apache Bean Validation & Google Guice
GuiceCon, March 19th, 2011
Simone Tripodi
simonetripodi@apache.org
http://people.apache.org/~simonetripodi

2. Apache Bean Validation
✗ Bean Validation Specifcation (JSR303)
implementation;
✗ Efort undergoing incubation at the ASF;
✗ TCK compliant;
✗ Works on JavaSE 5 or later;
✗ Donated to the ASF from Agimatec GmbH;
✗ Released under ASL 2.0 License.

3. Apache Bean Validation
&
Google Guice
✗ Bootstrap Apache Bean Validation using Google
Guice;
✗ Obtain javax.validation.ConstraintValidator
instances using the Google Guice Injector, to easily
support the DI;
✗ Require for javax.validation.* components
injection;
✗ Intercept methods and validate method arguments.

4. Bootstrapping
Guice.createInjector([...],
new org.apache.bval.guice.ValidationModule(),
[...]);
Simple enough?

5. obtain
javax.validation.ConstraintValidator
instances
class MyCustomValidator
Implements ConstraintValidator<MyAssert, MyType> {
private MyExternalService service;
@javax.inject.Inject
public setService(MyExternalService service) {
this.service = service;
}
public void initialize(MyAssert annotation) {
// do something
}
public boolean isValid(MyType value,
ConstraintValidatorContext context) {
return his.service.doSomething(value);
}
}

6. Require for javax.validation.*
components injection
class MyValidatorClient {
@javax.inject.Inject
private ValidatorFactory validatorFactory;
public void setValidatorFactory(ValidatorFactory
validatorFactory) {
this.validator = validator;
}
...
}

7. Require for javax.validation.*
components injection
class MyValidatorClient {
@javax.inject.Inject
private Validator validator;
public void setValidator(Validator validator) {
this.validator = validator;
}
...
}

8. Methods arguments validation
●the org.apache.bval.guice.ValidationModule comes with
an AOP interceptor automatically initialized;
●Based on @org.apache.bval.guice.Validate method
annotation
● Class<?>[] groups(): the groups have to be validated,
empty by default;
● boolean validateReturnedValue(): the returned object of
intercepted method has to be validated, false by default;
● Class<? Extends Throwable> rethrowExceptionAs(): the
exception re-thrown if a validation occurs,
javax.validation.ConstraintViolationException by
default;
● String exceptionMessage(): a custom error message
when throwing a custom exception.

9. Method arguments validation
@Validate(
groups = { Insert.class },
validateReturnedValue = true,
rethrowExceptionsAs = DummyException.class,
exceptionMessage = "Impossible adding Country{Name=%s, ISO2 Code=%s, ISO3 Code=%s}"
)
public Country insertCountry(@NotNull(groups = { Insert.class }) String name,
@NotNull(groups = { Insert.class })
@Size(max = 2, groups = { Insert.class, Update.class })
String iso2Code,
@NotNull(groups = { Insert.class })
@Size(max = 3, groups = { Insert.class, Update.class })
String iso3Code) {
Country country = new Country();
country.setName(name);
country.setIso2Code(iso2Code);
country.setIso3Code(iso3Code);
...
return country;
}

10. References
● Apache Bean Validation: http://incubator.apache.org/bval/
● Guice integration short guide:
http://incubator.apache.org/bval/cwiki/obtaining-a-validator.html
● Apache Bean Validation SVN:
https://svn.apache.org/repos/asf/incubator/bval/trunk

11. G R A Z I E :)