Question

Was wondering if there’s a way one can handle conversion errors in a lenient way.

Given a query that returns a List[ModelObject]

If there are 5 DBObjects retrieved, one of them is throwing a ConversionException when converted to ModelObject, is there a way to return the 4 convertible objects and provide a hook for the 1 conversion failure?

Answer 1

A bit late, but this answer might help someone else’s search

I agree it would be nice to do this on a policy basis – at the moment, if you get a single conversion error, you get no list at all. I think there are use cases where this is a valid need.

However, since you can’t, you need to register a custom converter for your ModelObject that converts leniently…

public class DBObjectToModelObjectConverter implements Converter<DBObject,ModelObject>{

    public ModelObject convert(DBObject s) {
        ... Read from the DBObject into your ModelObject and work around the bad data
    }
}

and then register this as a custom converter in your bean definitions. Something like:

<bean id="lenientModelReadConverter" class="com.my.DBObjectToModelObjectConverter"/>

<mongo:custom-converters>
   <mongo:converter ref="lenientModelReadConverter"/>
</mongo:custom-converters>