spring data neo4j rest projection returns null when using SpEL expression on nested object - spring-data-neo4j

Question

Consider the following output is produced:
Case 1: while retrieving the nested object from neo4j using spring data neo4j interface (projection)
{
"name": "Dhoni",
"currentLocation": {
"city": {
"name": "qwerqwer",
"regionalState": {
"state": {
"name": "zxvcxzcvc"
}
}
}
}
}
Projection Interface:
public interface PersonProjection {//Root
String getName();
CurrentLocationProjection getCurrentLocation();
public interface CurrentLocationProjection { // has relationship Props
CityProjection getCity(); // target object in entity mapping
interface CityProjection {
String getName();
RegionalStateProjection getRegionalState();
interface RegionalStateProjection { // has relationship Props
StateProjection getState(); // target object in entity mapping
interface StateProjection {
String getName();
}
}
}
}
}
Case 2: When i tried to get the nested values mapped to 1st level using SpEL, works fine as u can see below
public interface PersonProjection {//Root
String getName();
CurrentLocationProjection getCurrentLocation();
public interface CurrentLocationProjection {
#Value("#{target.city.name}")
String getCityName();
#Value("#{target.city.regionalState.state.name}")
String getStateName();
}
}
gives output as:
{
"name": "Deva",
"currentLocation": {
"cityName": "qwerqwer",
"stateName": "zxvcxzcvc"
}
}
Case 3:
Issue:
However, when i try to get nested values mapped to (root level / root node) itself using SpEL via #Value as below:
public interface PersonProjection {
String getName();
#Value("#{target.currentLocation.city.name}")
String getCityName();
#Value("#{target.currentLocation.city.regionalState.name}")
String getStateName();
}
expected output:
{
"name": "Dhoni",
"cityName": "qwerqwer",
"stateName": "zxvcxzcvc"
}
But, it throws the following error stating currentLocation is null as below: (but it has value)
WARN 13600 --- [nio-8080-exec-6] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: EL1007E: Property or field 'city' cannot be found on null; nested exception is com.fasterxml.jackson.databind.JsonMappingException: EL1007E: Property or field 'city' cannot be found on null (through reference chain: com.sun.proxy.$Proxy162["currentLocation"])]
I'm bit confused how it works in 1st-level and not in the root level?
could someone please point my mistake / guide me to achieve the expected output. Thanks.
Note: SDN (Spring Data Neo4j) version 6.1.2 for ref.

Answer 1

There was a bug in Spring Data Neo4j regarding Spring Expression Language using related entities that are not part of the projection.
https://github.com/spring-projects/spring-data-neo4j/issues/2325
tl;dr;
it is solved in Spring Data Neo4j 6.1.3