Spring data neo4j embedded property MappingException - spring

Question

I am fairly new to Neo4J; I am developing a project for learning purposes on which I am facing an issue that I am not managing to solve. My model might be somewhat relational DB influenced, but design issues aside, I believe however that what I am attempting should technically be done.
I have a NodeEntity Foo with an nested object Bar, converted to- and from String via ConversionService. In effect, Bar contains only one single String field, making the mapping trivial.
#NodeEntity
public class Foo {
#GraphId
private Long id;
#Indexed
private Bar bar;
...
}
public class Bar {
private String value;
...
}
When returning from a fairly simple Cypher query defined as follows on my repository:
#RepositoryRestResource(...)
public interface FooRepository
extends PagingAndSortingRepository<Foo, Long> {
...
#Query ("MATCH (foo) RETURN foo.bar")
Iterable<Bar> listBars ();
...
}
Conversion is configured as follows:
#Configuration
#ComponentScan(value = "de.h7r.playground.sd.neo4j",
excludeFilters = #ComponentScan.Filter({ Configuration.class }))
public class PKanbanConfiguration {
#Bean
public ConversionServiceFactoryBean conversionService ()
throws Exception {
final ConversionServiceFactoryBean csfb = new ConversionServiceFactoryBean ();
csfb.setConverters (getConverters ());
return csfb;
}
private Set<Converter> getConverters () {
return Sets.newHashSet (new BarConverter.ToString (), new BarConverter.FromString ());
}
}
Where the code for BarConverter is as follows.
public class BarConverter {
public static class FromString <S extends String, P extends Bar>
implements Converter<S, P> {
#Override
public P convert (final S source) {
// sets value into new instance of Bar and returns
}
}
public static class ToString <P extends Bar, S extends String>
implements Converter<P, S> {
#Override
public S convert (final P source) {
// gets value from Bar and returns
}
}
}
I am getting the following exception.
org.springframework.data.mapping.model.MappingException: Unknown persistent entity test.domain.Bar
at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:178)
...
Bar is indeed not a persitent entity nor should in my understanding be one. I grasp that this might have something to do with the defined return type of listBars; on the other hand, the repository if of Foos, so I had expected it to work. I would very much not like to fetch the whole set of nodes and then filter only the nested objects; the same way I would not like to have Bar replaced by String on Foo, since their type might have semantic relevance.
I am a bit lost as to how to returning all the property values for the existing nodes, specially since this query works as expected from neo4j-shell, so I see this as a pure Spring mapping issue.
I can add any further information that might prove helpful upon request.
Any help is very much appreciated.