Convert JSR-303 validation errors to Spring's BindingResult

Question

I have the following code in Spring controller:

@Autowired
private javax.validation.Validator validator;

@RequestMapping(value = "/submit", method = RequestMethod.POST)
public String submitForm(CustomForm form) {
    Set<ConstraintViolation<CustomForm>> errors = validator.validate(vustomForm);
    ...
}

Is it possible to map errors to Spring's BindingResult object without manually going through all the errors and adding them to the BindingResult? Something like this:

// NOTE: this is imaginary code
BindingResult bindingResult = BindingResult.fromConstraintViolations(errors);

I now it is possible to annotate CustomForm parameter with @Valid and let Spring inject BindingResult as another method's parameter, but it's not an option in my case.

// I know this is possible, but doesn't work for me
public String submitForm(@Valid CustomForm form, BindingResult bindingResult) {
    ...
}

Answer 1

A simpler approach could be to use Spring's abstraction org.springframework.validation.Validator instead, you can get hold of a validator by having this bean in the context:

<bean id="jsr303Validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean" />

@Autowired @Qualifier("jsr303Validator") Validator validator;

With this abstraction in place, you can use the validator this way, passing in your bindingResult:

validator.validate(obj, bindingResult);

Answer 2

Spring uses a SpringValidatorAdapter to convert javax.validation.ConstraintViolation objects to ObjectError or FieldError objects, as found in the binding result. The BindStatus then uses a message source (like the web application context itself) to translate the errors. In short, you could do:

SpringValidatorAdapter springValidator = new SpringValidatorAdapter(validator);
BindingResult bindingResult= new BeanPropertyBindingResult(myBeanToValidate, "myBeanName");
springValidator.validate(myBeanToValidate, bindingResult);

This is easier when writing a unit test, because you don't even need to create a Spring context.

Answer 3

Expanding on Kristiaan's answer, for testing purposes it is not necessary to create a spring context to validate using Spring's bindingResult. The following is an example:

public class ValidatorTest {

    javax.validation.Validator javaxValidator = Validation.buildDefaultValidatorFactory().getValidator();
    org.springframework.validation.Validator springValidator = new SpringValidatorAdapter(javaxValidator);

    @Test
    public void anExampleTest() {

    JSR303AnnotatedClassToTest   ctt  = new JSR303AnnotatedClassToTest( ..init vars..)

    ... test setup...

    WebDataBinder dataBinder = new WebDataBinder(ctt);
    dataBinder.setValidator(springValidator);
    dataBinder.validate();
    BindingResult bindingResult = dataBinder.getBindingResult(); 

    ... test analysis ...

    }
}

This approach doesn't require creating a binding result ahead of time, the dataBinder builds the right one for you.