cassandra-driver-mapping 3.1.0 MappingManager#mapper fails for Groovy class

[Jason Januzelli]

We implement our @Table mappings as Groovy classes.  This has worked fine with previous releases of the MappingManager thru release 3.0.3.  With the latest 3.1.0 release, it appears MappingManager requires there to be a column defined for the Groovy MetaClass property.  Comparing the source between 3.0.3 and 3.1.0, it looks like reflective inspection of the entity class has changed considerably within com.datastax.driver.mapping.AnnotationParser#parseEntity.  The new 3.1.0 source utilizes com.datastax.driver.mapping.ReflectionUtils.scanFieldsAndProperties which picks up the MetaClass property.  Creation of the Mapper fails since the actual table metadata does not include a corresponding column for the Groovy class's MetaClass.

Any suggestions?  Obviously we can convert all our mappings to Java classes but that's not desirable.

[Andrew Tolbert]

Hi Jason,

Could you share the exception stack trace and an example of a Groovy class that fails to map?  That may help us understand what we need to fix.

Thanks,

Andy

[Alexandre Dutra]

Hi Jason,

This is due to JAVA-636, that added support for mapped properties through both fields and getters, and also to the fact the the mapper has an opt-out approach when scanning for such properties, i.e, you need to explicitly exclude a property from being mapped by using the @Transient annotation.

Of course, this is a problem for auto-generated properties, like Groovy's "metaClass" property. I created JAVA-1279 to track this issue. In the meanwhile, I experimented with the following workaround: in each of your mapped classes, override the "metaClass" property and annotate it with @Transient:

@Transient
def MetaClass metaClass = super.metaClass;

It makes things work as far as the mapper is concerned, although I wouldn't guarantee that id does not introduce side-effects as I'm no Groovy expert.

Hope that helps!

Cheers,

Alexandre

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Alexandre Dutra

Driver & Tools Engineer @ DataStax

[Jason Januzelli]

We'll hold off on upgrading to the 3.1 driver for a bit and watch for any movement on JAVA-1279.  If we get to the point of needing to upgrade before JAVA-1279 is resolved, we'll evaluate whether to go with the proposed workaround or to refactor our mappings to Java classes.

Thanks.