CoffeeApplication.java

package com.example.molecues;

import java.util.Collections;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.Supplier;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.annotation.PersistenceConstructor;
import org.springframework.data.annotation.Version;
import org.springframework.data.neo4j.core.Neo4jTemplate;
import org.springframework.data.neo4j.core.schema.Id;
import org.springframework.data.neo4j.core.schema.Node;
import org.springframework.data.neo4j.core.schema.Relationship;
import org.springframework.stereotype.Component;

@Node
class Molecule {

	private static final Supplier<Long> sequenceGenerator = new Supplier<>() {

		private final AtomicLong source = new AtomicLong(0L);

		@Override
		public Long get() {
			return source.incrementAndGet();
		}
	};

	@Id
	private final Long id;

	@Version
	private Long version;

	private String name;

	@Relationship(direction = Relationship.Direction.OUTGOING, type = "—")
	private Set<Molecule> relatedObjects = new HashSet<>();

	Molecule(String name) {
		this(sequenceGenerator.get(), name);
	}

	@PersistenceConstructor Molecule(Long id, String name) {
		this.id = id;
		this.name = name;
	}

	public Long getId() {
		return id;
	}

	public Long getVersion() {
		return version;
	}

	public String getName() {
		return name;
	}

	public Set<Molecule> getRelatedObjects() {
		return Collections.unmodifiableSet(relatedObjects);
	}

	private void setRelatedObjects(Set<Molecule> relatedObjects) {
		this.relatedObjects = relatedObjects;
	}

	public void relate(Molecule object) {
		this.relatedObjects.add(object);
		object.relatedObjects.add(this);
	}

	public void relateUni(Molecule object) {
		this.relatedObjects.add(object);
	}

	@Override
	public boolean equals(Object o) {
		if (this == o) {
			return true;
		}
		if (o == null || getClass() != o.getClass()) {
			return false;
		}
		Molecule that = (Molecule) o;
		return id.equals(that.id);
	}

	@Override
	public int hashCode() {
		return Objects.hash(id);
	}
}

@Node
class C extends Molecule {

	C() {
		super("");
	}

	@PersistenceConstructor
	private C(Long id, String name) {
		super(id, name);
	}
}

@Component
class Brew implements CommandLineRunner {

	private final Neo4jTemplate neo4jTemplate;

	public Brew(Neo4jTemplate neo4jTemplate) {
		this.neo4jTemplate = neo4jTemplate;
	}

	@Override
	public void run(String... args) throws Exception {

		neo4jTemplate.deleteAll(Molecule.class);

		var o = new Molecule("O");
		var c1 = new C();
		var c2 = new C();
		var c3 = new C();
		var n = new Molecule("N");
		var ch3 = new Molecule("CH3");
		var c4 = new C();
		var o2 = new Molecule("O");
		var n2 = new Molecule("N");
		var h3c = new Molecule("H3C");
		var n3 = new Molecule("N");
		var n4 = new Molecule("N");
		var c5 = new C();
		var ch3_2 = new Molecule("CH3");

		o.relate(c1);
		c1.relateUni(c2);
		c2.relate(c3);
		c2.relateUni(n3);
		n3.relateUni(c5);
		n3.relateUni(ch3_2);
		c3.relateUni(n);
		c3.relateUni(n4);
		n4.relate(c5);
		n.relateUni(ch3);
		n.relateUni(c4);
		c4.relate(o2);
		c4.relateUni(n2);
		n2.relateUni(h3c);
		n2.relateUni(c1);

		neo4jTemplate.save(o);

		o = neo4jTemplate.findById(o.getId(), Molecule.class).get();
	}
}

// Latest Spring Data Neo4j 6.2-SNAPSHOT is needed to run this successfully…
@SpringBootApplication
public class CoffeeApplication {

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