Menampilkan Data Bertingkat ke JTree Menggunakan Hibernate

Category.java

@Entity
@Table(name = "stripbandunk_category")
public class Category implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue
    @Column(name = "id")
    private Long id;

    @Column(name = "name")
    private String name;

    @ManyToOne
    @JoinColumn(name = "parent")
    private Category parent;

    @OneToMany(mappedBy = "parent")
    private List<Category> categories = new ArrayList<Category>(0);

    // getter dan setter

}

CategoryTreeModel.java

public class CategoryTreeModel implements TreeModel {

    private Object root;

    private List<Category> categories;

    public CategoryTreeModel(Object root, List<Category> categories) {
        this.root = root;
        this.categories = categories;
    }

    public Object getRoot() {
        return root;
    }

    public Object getChild(Object parent, int index) {
        if (parent == root) {
            return categories.get(index);
        } else if (parent instanceof Category) {
            Category category = (Category) parent;
            return category.getCategories().get(index);
        } else {
            return null;
        }
    }

    public int getChildCount(Object parent) {
        if (parent == root) {
            return categories.size();
        } else if (parent instanceof Category) {
            Category category = (Category) parent;
            return category.getCategories().size();
        } else {
            return 0;
        }
    }

    public boolean isLeaf(Object node) {
        if (node instanceof Category) {
            Category category = (Category) node;
            return category.getCategories().isEmpty();
        } else {
            return false;
        }
    }

    public void valueForPathChanged(TreePath path, Object newValue) {
        // do nothing
    }

    public int getIndexOfChild(Object parent, Object child) {
        if (parent instanceof Category) {
            Category parentcategory = (Category) parent;
            return parentcategory.getCategories().indexOf(child);
        } else if (parent == root) {
            return categories.indexOf(child);
        } else {
            return 0;
        }
    }

    public void addTreeModelListener(TreeModelListener l) {
        // do nothing
    }

    public void removeTreeModelListener(TreeModelListener l) {
        // do nothing
    }
}

Form.java

Session session = HibernateHelper.getSessionFactory().openSession();

@SuppressWarnings("unchecked")
List<Category> list = session.createQuery("from Category a where a.parent is null").list();
CategoryTreeModel treeModel = new CategoryTreeModel("Root", list);

jTreeCategory.setModel(treeModel);