JSR 303 - Hibernate Validation 4.2.0 - UnexpectedTypeException - @Valid and @Size in combination

Question

I have strange behaviour using Hibernate Validator (JSR 303) and annotating a property of type java.util.List

Following Code Base:

public class A {
  @Valid @NotNull @Size(min=1, max=15)
  private List<B<?>> validList = new ArrayList<B<?>>();
  ...
}

If I start the validation I get the following exception:

javax.validation.UnexpectedTypeException: No validator could be found for type: B
at org.hibernate.validator.engine.ConstraintTree.verifyResolveWasUnique(ConstraintTree.java:383)
at org.hibernate.validator.engine.ConstraintTree.findMatchingValidatorClass(ConstraintTree.java:364)
at org.hibernate.validator.engine.ConstraintTree.getInitializedValidator(ConstraintTree.java:313)
at org.hibernate.validator.engine.ConstraintTree.validateConstraints(ConstraintTree.java:144)
at org.hibernate.validator.engine.ConstraintTree.validateConstraints(ConstraintTree.java:117)
at org.hibernate.validator.metadata.MetaConstraint.validateConstraint(MetaConstraint.java:84)
at org.hibernate.validator.engine.ValidatorImpl.validateConstraint(ValidatorImpl.java:452)
at org.hibernate.validator.engine.ValidatorImpl.validateConstraintsForDefaultGroup(ValidatorImpl.java:397)
at org.hibernate.validator.engine.ValidatorImpl.validateConstraintsForCurrentGroup(ValidatorImpl.java:361)
at org.hibernate.validator.engine.ValidatorImpl.validateInContext(ValidatorImpl.java:313)
at org.hibernate.validator.engine.ValidatorImpl.validateCascadedConstraint(ValidatorImpl.java:613)
at org.hibernate.validator.engine.ValidatorImpl.validateCascadedConstraints(ValidatorImpl.java:478)
at org.hibernate.validator.engine.ValidatorImpl.validateInContext(ValidatorImpl.java:322)
at org.hibernate.validator.engine.ValidatorImpl.validate(ValidatorImpl.java:139)

If I change my code (and therefore unfortunately my semantic) as follows:

public class A {
  @Valid @NotNull @Size(min=0, max=15)
  private List<B<?>> validList = new ArrayList<B<?>>();
  ...
}

everything validates fine without exception.

Which part do I miss? Has anybody an idea why this doesn't work?

I have found out what the problem was. I have a customized constraint on the class B

@CustomConstraint
public class B {
}

the constraint:

@Target( { METHOD, FIELD, ANNOTATION_TYPE })
@Retention(RUNTIME)
@Constraint(validatedBy = CustomConstraintValidator.class)
@Documented
public @interface CustomConstraint {

  String message() default "{com.mycompany.constraints.checkcase}";

  Class<?>[] groups() default {};

  Class<? extends Payload>[] payload() default {};

}

and the validator:

public class CheckCaseValidator implements ConstraintValidator<CustomConstraint, B<? extends C>> {

... //validation stuff here

}

after I have removed the generics expression from the validator class:

public class CheckCaseValidator implements ConstraintValidator<CustomConstraint, B> {

... //validation stuff here

}

everything worked fine.

Hope that other people find this helpful. Best Regards, Walter

Answer 1

The javadoc ( http://jcp.org/en/jsr/detail?id=303 ) for javax.validation.ConstraintValidator<A, T> says:

Defines the logic to validate a given constraint A for a given object type T. Implementations must comply to the following restriction:

• T must resolve to a non parameterized type
• or generic parameters of T must be unbounded wildcard types

1. (T must resolve to a non parameterized type)

   that's why ConstraintValidator<CustomConstraint, B> works

2. (or generic parameters of T must be unbounded wildcard types)

   does not seem to work, as ConstraintValidator<CustomConstraint, B<?>> does not work either

I also found a different version of the javadoc where the second restriction is left out. So it could be that the official javadoc is just wrong. If you are curious, file a bug report for Hibernate Validator (it's the reference implementation). If you don't - I will ;-)