[bv-dev] BVAL-265 - Expose settings defined in XML in the Configuration API

[Hardy Ferentschik]

Hi,

comments inline

On Jul 2, 2012, at 8:35 PM, Matt Benson wrote:

> Hi all,
>  Sorry for my extreme tardiness in doing the backing research on this
> issue.  I am fine with the standing changes, so far as they go;
> however it seems like this could also be an opportunity of sorts.  If
> the Configuration object is going to expose the ConfigurationSource
> (and thereby the data corresponding to that mined from the XML
> configuration), it would seem to move the responsibility of parsing
> the XML and eliminate the need for ConfigurationState#getMappingStreams().

I don't think that the changes introduced by ConfigurationSource have an effect on 
ConfigurationState#getMappingStreams. Yes, this methods provides input streams to
the configuration files defined in validation.xml, but it is also a general programmatic 
configuration source to configure Bean Validation.

Whether it was/is a good choice to use input streams over strings (defining file paths)
is debatable. I think the idea was to allow other input sources than just files.
Generally I think this is a good idea,  but of course working with InputStream creates 
another set of problems. Despite these problems I don't think we should change anything
regarding ConfigurationState#getMappingStreams(), since it servers a different purpose 
than ConfigurationSource and changing it would break backwards compatibility.

Also there are work arounds for the one issue you are referring to (see comment below).

>  This method is AFAICT the
> place that complicates the building of multiple ValidatorFactory
> instances from a single Configuration, which was the subject of a
> thread which I cannot currently find, but whose participants I recall
> as having included Gunnar and myself

I think you are referring to HV-563 ("Enable Configuration#buildValidatorFactory() to be callable several times").

There was indeed an issue with building multiple ValidatorFactory instances from a single 
Configuration instance (at least in Hibernate Validator). However, we found a way to solve this, by
checking whether the provided InputStream supports marking [2]. If it does than there is no problem and if it doesn't
we wrap the stream in a BufferedInputStream which does. Once you have a markable stream you can mark, read 
and finally reset it [3]. This way you can reuse the Configuration multiple times.


--Hardy


[1] https://hibernate.onjira.com/browse/HV-563
[2] https://github.com/hibernate/hibernate-validator/blob/master/engine/src/main/java/org/hibernate/validator/internal/engine/ConfigurationImpl.java#L167
[3] https://github.com/hibernate/hibernate-validator/blob/master/engine/src/main/java/org/hibernate/validator/internal/xml/XmlMappingParser.java#L614