Spring-Neo4j: Relationship is not retrieving correctly - neo4j

Question

I have an entity class that refers to itself as the parent class.
#NodeEntity
public class Config {
#Id
#GeneratedValue
private Long id;
#Relationship(type = "OVERRIDES", direction="INCOMING")
private Config parentConfig;
#Properties(allowCast=true, prefix="properties", delimiter=".")
private Map<String, String> properties;
....
}
When I run the built-in findById() method in my java code, the "parentConfig" is always the same as the child object. I never see the other end of the relationship. What am I doing wrong?

Answer 1

this works as expected but depends on how you want to model your config.
Assuming you want to express "Child overwrites parent config", which I would model as
CREATE (c:Config {name: 'Parent'}) <- [:OVERRIDES] - (c2:Config {name: 'Child'})
This gives you:
Then you must model the association as outgoing from the child object like this:
import org.neo4j.ogm.annotation.GeneratedValue;
import org.neo4j.ogm.annotation.Id;
import org.neo4j.ogm.annotation.Relationship;
public class Config {
#Id
#GeneratedValue
private Long id;
private String name;
#Relationship(type = "OVERRIDES", direction = Relationship.OUTGOING)
private Config parent;
public Long getId() {
return id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Config getParent() {
return parent;
}
#Override public String toString() {
return "Config{" +
"name='" + name + '\'' +
'}';
}
}
Turning this into a full example:
import java.util.Optional;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.neo4j.repository.Neo4jRepository;
import org.springframework.stereotype.Component;
interface ConfigRepo extends Neo4jRepository<Config, Long> {
Optional<Config> findOneByName(String name);
}
#Component
class Example implements CommandLineRunner {
#Autowired
private ConfigRepo configRepo;
#Override
public void run(String... args) throws Exception {
configRepo.findOneByName("Parent").ifPresent(c -> {
System.out.println("Config " + c + " has parent " + c.getParent());
});
configRepo.findOneByName("Child").ifPresent(c -> {
System.out.println("Config " + c + " has parent " + c.getParent());
});
}
}
#SpringBootApplication
public class SorecassocApplication {
public static void main(String[] args) {
SpringApplication.run(SorecassocApplication.class, args);
}
}
Will return
2018-10-10 09:20:21.960 INFO 3832 --- [ main] o.n.o.drivers.bolt.request.BoltRequest : Request: MATCH (n:`Config`) WHERE n.`name` = { `name_0` } WITH n RETURN n,[ [ (n)-[r_o1:`OVERRIDES`]->(c1:`Config`) | [ r_o1, c1 ] ] ], ID(n) with params {name_0=Parent}
Config Config{name='Parent'} has parent null
2018-10-10 09:20:21.984 INFO 3832 --- [ main] o.n.o.drivers.bolt.request.BoltRequest : Request: MATCH (n:`Config`) WHERE n.`name` = { `name_0` } WITH n RETURN n,[ [ (n)-[r_o1:`OVERRIDES`]->(c1:`Config`) | [ r_o1, c1 ] ] ], ID(n) with params {name_0=Child}
Config Config{name='Child'} has parent Config{name='Parent'}
If you model the relationship as INCOMING from the perspective of the child, than you have to inverse the relation ship in the nodes. Otherwise the output is as:
2018-10-10 09:22:54.929 INFO 3837 --- [ main] o.n.o.drivers.bolt.request.BoltRequest : Request: MATCH (n:`Config`) WHERE n.`name` = { `name_0` } WITH n RETURN n,[ [ (n)<-[r_o1:`OVERRIDES`]-(c1:`Config`) | [ r_o1, c1 ] ] ], ID(n) with params {name_0=Parent}
Config Config{name='Parent'} has parent Config{name='Child'}
2018-10-10 09:22:54.951 INFO 3837 --- [ main] o.n.o.drivers.bolt.request.BoltRequest : Request: MATCH (n:`Config`) WHERE n.`name` = { `name_0` } WITH n RETURN n,[ [ (n)<-[r_o1:`OVERRIDES`]-(c1:`Config`) | [ r_o1, c1 ] ] ], ID(n) with params {name_0=Child}
Config Config{name='Child'} has parent null
Here are my dependencies to turn the examples into a running application:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>sorecassoc</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>sorecassoc</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.5.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-neo4j</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
Please let me know if this solves your problem.