Cannot use enum in repository query (neo4j/Spring Data) - neo4j

Question

I'm having a problem querying based on an Enum property of my NodeEntity.
The NodeEntity in question is defined:
#NodeEntity(label = "Entity")
public class MyEntity {
#GraphId
private Long internalId;
....
private State state;
#Transient
public enum State {
STATEONE, STATETWO, STATETHREE
}
....
It saves without a problem, the state Enum represented perfectly, and I can query using other properties (Strings) with no problem at all. However the problem is the following query in a repository:
#Query("MATCH (entity:Entity {state:{0}})" +
"RETURN entity")
List<MyEntity> findByState(MyEntity.State state)
i.e. find all entities with the given state.
There's no exception, however using this simply returns a List of 0 Entities.
I've tried all kinds of variations on this, using a WHERE clause for example, with no luck.
The Entities are persisted properly, using findAll() in the same test returns the expected List of Entities with their states exactly as I would expect.
Any thoughts?

Answer 1

Not quite sure what the value #Transient adds to the enum. It is anyway not persistable as a node or relationship in Neo4j. It is sufficient to define the field as one that should persist with
private State state;
and leave off the #Transient annotation from the enum.
With it, SDN ignores the field sent to the derived query.
However, if you have a good reason to mark the enum #Transient, please do share it and we'll re-visit this case.

Answer 2

There is a general problems using spring data rest interface to search on enum fields. Just using the enum-to-string converter cannot work for search where you want to find if the value is IN a collection of values:
public interface AppointmentRepository extends Neo4jRepository<Appointment, Long> {
Page<Appointment> findByDayOfWeekIn(#Param("days") List<DayOfWeek> days, Pageable pageable);
}
The above does not work out of the box because neo4j will try to convert a List to your property type: DayOfWeek
In order to work around this I needed a custom converter that handles both requests providing collection of values (the search) and single values (the normal read and write entity):
#SuppressWarnings({ "unchecked", "rawtypes" })
public abstract class SearchQueryEnumConverter<T extends Enum> {
private Class<T> enumType;
public SearchQueryEnumConverter() {
enumType = (Class<T>) ((ParameterizedType) this.getClass()).getActualTypeArguments();
}
public Object toGraphProperty(Object value) {
if (Collection.class.isAssignableFrom(value.getClass())) {
List<T> values = (List<T>) value;
return values.stream().map(Enum::name).collect(Collectors.toList());
}
return ((Enum) value).name();
}
public Object toEntityAttribute(Object value) {
if (Collection.class.isAssignableFrom(value.getClass())) {
List<String> values = (List<String>) value;
return values.stream().map(v -> (T) T.valueOf(enumType, v)).collect(Collectors.toList());
}
return (T) T.valueOf(enumType, value.toString());
}
}
The abstract converter can be reified by all enums, and used as parameter of the #Convert annotation:
public enum EnumType {
VALUE_A, VALUE_B;
public static class Converter extends SearchQueryEnumConverter<EnumType> implements AttributeConverter {
}
}
#NodeEntity
public Entity {
#Property
#Convert(EnumType.Converter.class)
EnumType type;
}