Stephen Bayliss | 27 Jan 11:20

[fcrepo-dev] Fedora validation enhancements - FCREPO-1026

I've made some validation enhancements as per https://jira.duraspace.org/browse/FCREPO-1026, these are currently in the fcrepo-1026 branch on GitHub.  Some documentation is in the Fedora 3.6 documentation space at https://wiki.duraspace.org/display/FEDORA36/Validation
 
I've some questions on how far to take this, so feedback is welcomed.
 
The current implementation:
 
* allows configuration of the XML ingest validation via a new DOManager fedora.fcfg parameter (with a suitable warning in the documentation about decreasing the level of validation)
* allows all objects to be validated when they are modified, with the API operation being failed if the resulting object would be invalid
 
Object validation is configured via spring (see doobjectvalidator.xml in the server/config/spring directory) - by default it is turned off, so out-of-the-box there's no performance hit.  This feature enables for instance ECM validation to be turned on for every object modification to enforce repository content conformance with the CModel specification via ECM.  Certainly this isn't for everyone, but there are use cases.  Custom validators can be written and added that validate the Java Fedora object (rather than the XML).  Any number of validators can be added, these will execute in turn until (if) one fails.
 
Questions and thoughts:
 
* HTTP response code for REST API operations:  Currently if an ingest fails XML validation this is reported via HTTP status code 500 (Server Error).  To maintain consistency with the existing behaviour, object validation failures will also result in this code, with the text of the exception containing details of the validation failure.  I'd suggest that maybe 400 - Bad Request [1] might be more appropriate for both of these; but this would essentially represent a REST API change - would that be acceptable for a Fedora 3.6 release?  If this change was made I'd suggest implementing this by catching ObjectValidityException at the API level, and extending this exception to contain details of the validation failure for the response body (rather than the 500 exception reporting that occurs currently).
 
* Validate API method.  Currently this performs the ECM validation as it did in previous releases.  This could be modified to perform object validation as specified in the spring config for this - would this make sense?  It should be configurable so that custom validation can be plugged into the validate API method *without* enforcing validation on object commital of course.
 
* Comments on the implementation and code in that branch are most welcome
 
Thanks
Steve
 
 
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