Neo4j でデータアクセス

$ brew install neo4j

$ neo4j start

Starting Neo4j.
Started neo4j (pid 96416). By default, it is available at http://localhost:7474/
There may be a short delay until the server is ready.
See /usr/local/Cellar/neo4j/<version>/libexec/logs/neo4j.log for current status.

docker run \
  --publish=7474:7474 --publish=7687:7687 \
  --volume=$HOME/neo4j/data:/data \
  --env NEO4J_AUTH=neo4j/spring+neo4j \
  neo4j

package com.example.accessingdataneo4j;

import java.util.Collections;
import java.util.HashSet;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;

import org.jspecify.annotations.Nullable;
import org.springframework.data.neo4j.core.schema.GeneratedValue;
import org.springframework.data.neo4j.core.schema.Id;
import org.springframework.data.neo4j.core.schema.Node;
import org.springframework.data.neo4j.core.schema.Relationship;

@Node
public class Person {

  @Id
  @GeneratedValue
  private @Nullable Long id;

  private String name;

  private Person() {
    // Empty constructor required as of Neo4j API 2.0.5
  };

  public Person(String name) {
    this.name = name;
  }

  @Relationship(type = "REFERRED")
  public Set<Person> referrals;

  public void referred(Person person) {
    if (referrals == null) {
      referrals = new HashSet<>();
    }
    referrals.add(person);
  }

  public String toString() {

    return this.name + " referred => "
      + Optional.ofNullable(this.referrals).orElse(
          Collections.emptySet()).stream()
            .map(Person::getName)
            .collect(Collectors.toList());
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }
}

package com.example.accessingdataneo4j;

import java.util.List;

import org.jspecify.annotations.Nullable;
import org.springframework.data.neo4j.repository.Neo4jRepository;

public interface PersonRepository extends Neo4jRepository<Person, Long> {

  @Nullable
  Person findByName(String name);

  List<Person> findByReferralsName(String name);
}

spring.neo4j.uri=bolt://localhost:7687
spring.neo4j.authentication.username=neo4j
spring.neo4j.authentication.password=spring+neo4j

package com.example.accessingdataneo4j;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class AccessingDataNeo4jApplication {

  public static void main(String[] args) {
    SpringApplication.run(AccessingDataNeo4jApplication.class, args);
  }

}

package com.example.accessingdataneo4j;

import java.util.Arrays;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.data.neo4j.repository.config.EnableNeo4jRepositories;

@SpringBootApplication
@EnableNeo4jRepositories
public class AccessingDataNeo4jApplication {

	private final static Logger log = LoggerFactory.getLogger(AccessingDataNeo4jApplication.class);

	public static void main(String[] args) throws Exception {
		SpringApplication.run(AccessingDataNeo4jApplication.class, args);
		System.exit(0);
	}

	@Bean
	CommandLineRunner demo(PersonRepository personRepository) {
		return args -> {

			personRepository.deleteAll();

			Person greg = new Person("Greg");
			Person roy = new Person("Roy");
			Person craig = new Person("Craig");

			List<Person> team = Arrays.asList(greg, roy, craig);

			log.info("Before linking up with Neo4j...");

			team.stream().forEach(person -> log.info("\t" + person.toString()));

			personRepository.save(greg);
			personRepository.save(roy);
			personRepository.save(craig);

			greg = personRepository.findByName(greg.getName());
			greg.referred(roy);
			greg.referred(craig);
			personRepository.save(greg);

			roy = personRepository.findByName(roy.getName());
			roy.referred(craig);
			personRepository.save(roy);

			// Craig has no referrals yet

			log.info("Lookup each person by name...");
			team.stream().forEach(person -> log.info(
					"\t" + personRepository.findByName(person.getName()).toString()));

			List<Person> referrers = personRepository.findByReferralsName(craig.getName());
			log.info("The following referred Craig...");
			referrers.stream().forEach(person -> log.info("\t" + person.getName()));
		};
	}

}

Before linking up with Neo4j...
	Greg referred => []
	Roy referred => []
	Craig referred => []

Lookup each person by name...
	Greg referred => [Roy, Craig]
	Roy referred => [Craig]
	Craig referred => []

The following referred Craig...
	Greg
	Roy