Dropwizard API资源中的@Valid

Question

I am trying to use @Valid in dropwizard before the object is consumed by the API. However, none of the attributes of the object are getting validated as it seems validation is not happening? Am I missing something in adding a configuration to enable it?

FYI: We have implemented our own message body reader which extends from javax.ws.rs.ext.MessageBodyReader for mapping JSON to object.

Answer 1

You need to store a javax.validation.Validator object in your MessageBodyReader and use it to validate classes annotated with @Valid in your readFrom() method. This is how Dropwizard's Jackson Provider does it.

So the code looks something like this:

private static final Class<?>[] DEFAULT_GROUP_ARRAY = new Class<?>[]{ Default.class };
private final XmlMapper mapper;
private final Validator validator;

public MyMessageBodyReader(XmlMapper mapper, Validator validator) {
    this.validator = validator;
    this.mapper = mapper;
    setMapper(mapper);
}

@Override
public Object readFrom(Class<Object> type,
                       Type genericType,
                       Annotation[] annotations,
                       MediaType mediaType,
                       MultivaluedMap<String, String> httpHeaders,
                       InputStream entityStream) throws IOException {
    return validate(annotations, super.readFrom(type,
            genericType,
            annotations,
            mediaType,
            httpHeaders,
            entityStream));
}

private Object validate(Annotation[] annotations, Object value) {
    final Class<?>[] classes = findValidationGroups(annotations);

    if (classes != null) {
        final Set<ConstraintViolation<Object>> violations = validator.validate(value, classes);
        if (!violations.isEmpty()) {
            throw new ConstraintViolationException("The request entity had the following errors:",
                    ConstraintViolations.copyOf(violations));
        }
    }

    return value;
}

private Class<?>[] findValidationGroups(Annotation[] annotations) {
    for (Annotation annotation : annotations) {
        if (annotation.annotationType() == Valid.class) {
            return DEFAULT_GROUP_ARRAY;
        } else if (annotation.annotationType() == Validated.class) {
            return  ((Validated) annotation).value();
        }
    }
    return null;
}

I have an example here , where I've written a custom XML Jackson Reader + Writer with Validation support.