CREATE TABLE t_directory (
  id           number(7) NOT NULL,
  parent_id    number(7),
  is_directory number(7),
  "name"       varchar2(50),

  CONSTRAINT pk_t_directory PRIMARY KEY (ID),
  CONSTRAINT pk_t_directory_self FOREIGN KEY (PARENT_ID) 
    REFERENCES t_directory(ID) ON DELETE CASCADE
);

INSERT INTO t_directory VALUES                     ( 1, null, 1, 'C:');
    INSERT INTO t_directory VALUES                 ( 2,    1, 1, 'eclipse');
        INSERT INTO t_directory VALUES             ( 3,    2, 1, 'configuration');
        INSERT INTO t_directory VALUES             ( 4,    2, 1, 'dropins');
        INSERT INTO t_directory VALUES             ( 5,    2, 1, 'features');
        INSERT INTO t_directory VALUES             ( 7,    2, 1, 'plugins');
        INSERT INTO t_directory VALUES             ( 8,    2, 1, 'readme');
            INSERT INTO t_directory VALUES         ( 9,    8, 0, 'readme_eclipse.html');
        INSERT INTO t_directory VALUES             (10,    2, 1, 'src');
        INSERT INTO t_directory VALUES             (11,    2, 0, 'eclipse.exe');
        INSERT INTO t_directory VALUES             (12,    2, 0, 'eclipse.ini');
    INSERT INTO t_directory VALUES                 (13,    1, 1, 'Program Files');
        INSERT INTO t_directory VALUES             (14,   13, 1, 'Internet Explorer');
            INSERT INTO t_directory VALUES         (15,   14, 1, 'de-DE');
            INSERT INTO t_directory VALUES         (16,   14, 0, 'ielowutil.exe');
            INSERT INTO t_directory VALUES         (17,   14, 0, 'iexplore.exe');
        INSERT INTO t_directory VALUES             (18,   13, 1, 'Java');
            INSERT INTO t_directory VALUES         (19,   18, 1, 'jre6');
                INSERT INTO t_directory VALUES     (20,   19, 1, 'bin');
                    INSERT INTO t_directory VALUES (21,   20, 0, 'java.exe');
                    INSERT INTO t_directory VALUES (22,   20, 0, 'javaw.exe');
                    INSERT INTO t_directory VALUES (23,   20, 0, 'javaws.exe');
                INSERT INTO t_directory VALUES     (24,   19, 1, 'lib');
                    INSERT INTO t_directory VALUES (25,   24, 0, 'javaws.jar');
                    INSERT INTO t_directory VALUES (26,   24, 0, 'rt.jar');

SELECT *
FROM t_directory
CONNECT BY PRIOR id = parent_id
START WITH parent_id IS NULL
ORDER SIBLINGS BY "name"

DSL.using(configuration)
   .select()
   .from(T_DIRECTORY)
   .connectBy(prior(T_DIRECTORY.ID).eq(T_DIRECTORY.PARENT_ID))
   .startWith(T_DIRECTORY.PARENT_ID.isNull())
   .orderSiblingsBy(T_DIRECTORY.NAME)

@Entity
@Table(name = "t_directory")
public class JPADirectory {

    @Id
    public int                id;

    @ManyToOne
    @JoinColumn(name = "parent_id")
    public JPADirectory       parent;

    @OneToMany(mappedBy = "parent")
    public List<JPADirectory> children;

    @Column(name = "`name`")
    public String             name;
}

List<JPADirectory> result = em.createNativeQuery(sql, JPADirectory.class).getResultList();