20210422.source.java

@Entity
@Table(name = "nodes", schema = "playground", catalog = "postgres")
public class NodesEntity {
    @Id
    @Column(name = "id", nullable = false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    @Basic
    @Column(name = "node_name", nullable = false, length = 10)
    private String nodeName;

    @OneToMany(mappedBy = "fromNode", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    public Set<EdgesEntity> edges = new LinkedHashSet<>();

    public int getId() { return id; }
    public void setId(int id) { this.id = id; }

    public String getNodeName() { return nodeName; }
    public void setNodeName(String nodeName) { this.nodeName = nodeName; }
}

@Entity
@Table(name = "edges", schema = "playground", catalog = "postgres")
public class EdgesEntity {
    @Id
    @Column(name = "id", nullable = false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    @ManyToOne
    @JoinColumn(name = "from_node_id", nullable = false)
    private NodesEntity fromNode;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "to_node_id", nullable = false)
    private NodesEntity toNode;

    @Basic
    @Column(name = "type", nullable = false, length = 20)
    private String type;

    public int getId() { return id; }
    public void setId(int id) { this.id = id; }

    public NodesEntity getFromNode() { return fromNode; }
    public void setFromNode(NodesEntity fromNode) { this.fromNode = fromNode; }

    public NodesEntity getToNode() { return toNode; }
    public void setToNode(NodesEntity toNode) { this.toNode = toNode; }

    public String getType() { return type; }
    public void setType(String type) { this.type = type; }
}

public static void main(final String[] args) throws Exception {
    final Session session = getSession();
    try {
        NodesEntity nodeA = new NodesEntity();
        nodeA.setNodeName("A");

        NodesEntity nodeB = new NodesEntity();
        nodeB.setNodeName("B");

        EdgesEntity entityAToB = new EdgesEntity();
        entityAToB.setFromNode(nodeA);
        entityAToB.setToNode(nodeB);
        entityAToB.setType("parent");

        nodeA.edges.add(entityAToB);

        EdgesEntity entityBToA = new EdgesEntity();
        entityBToA.setFromNode(nodeB);
        entityBToA.setToNode(nodeA);
        entityBToA.setType("child");

        nodeB.edges.add(entityBToA);

        session.save(nodeA);
    } finally {
        session.close();
    }
}