SEVERE: an assertion failure occured (this may indicate a bug in Hibernate, but is more likely due to unsafe use of the session)
org.hibernate.AssertionFailure: Table SUBCATEGORY not found
        at org.hibernate.persister.entity.JoinedSubclassEntityPersister.getTableId(JoinedSubclassEntityPersister.java:458)
        at org.hibernate.persister.entity.JoinedSubclassEntityPersister.<init>(JoinedSubclassEntityPersister.java:237)
        at org.hibernate.persister.PersisterFactory.createClassPersister(PersisterFactory.java:58)

@ManyToOne and
  @JoinTable(name = "SUBCATEGORY",
             joinColumns = {@JoinColumn(name = "CHILDID")},
             inverseJoinColumns = {@JoinColumn(name = "PARENTID")})
  private Category parent;

  @ManyToMany
  @JoinTable(name = "SUBCATEGORY",
             joinColumns = { @JoinColumn(name = "PARENTID")},
             inverseJoinColumns = { @JoinColumn(name = "CHILDID")})

CREATE TABLE IF NOT EXISTS Category(
    CategoryId            bigint(4)     NOT NULL    auto_increment,
    Title                     varchar(30)   NOT NULL,
    CategoryLevel         bigint(1)     NOT NULL    DEFAULT '1',
    CategoryType         varchar(20)    NOT NULL    DEFAULT 'Category',
    PRIMARY KEY (CategoryId)
) ENGINE=INNODB;

CREATE TABLE IF NOT EXISTS Chapter(
    ChapterId             bigint(4)     NOT NULL    auto_increment,
    ChapterOrder          int(4)        NOT NULL    DEFAULT '0',
    BookId                bigint(4)     NOT NULL,
    PRIMARY KEY (ChapterId),
    FOREIGN KEY (ChapterId) REFERENCES Category(CategoryId) ON UPDATE CASCADE,
    FOREIGN KEY (BookId) REFERENCES Book(BookId) ON UPDATE CASCADE
) ENGINE=INNODB;

CREATE TABLE IF NOT EXISTS SubCategory(
    SubCategoryId     bigint(4)     NOT NULL   auto_increment,
    ParentId          bigint(4)     NOT NULL,
    ChildId           bigint(4)     NOT NULL,
    PRIMARY KEY (SubCategoryId),
    FOREIGN KEY (ParentId) REFERENCES Category(CategoryId) ON UPDATE CASCADE,
    FOREIGN KEY (ChildId) REFERENCES Category(CategoryId) ON UPDATE CASCADE
) ENGINE=INNODB;

@Entity
@Table(name = "CHAPTER")
@PrimaryKeyJoinColumn(name="CHAPTERID", referencedColumnName="CATEGORYID")
public class Chapter extends Category {

  @Column(name = "CHAPTERORDER")
  private Long chapterOrder;
 
  @ManyToOne
  @JoinColumn(name = "BOOKID")
  private Book book;

  public Chapter() {super();}

@Entity
@Table(name = "CATEGORY")
@Inheritance(strategy=InheritanceType.JOINED)
public class Category implements Serializable {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "CATEGORYID")
  private Long categoryId;

  @Column(name = "TITLE")
  private String title;
 
  @Column(name = "CATEGORYLEVEL")
  private Long categoryLevel;

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

  @ManyToOne
  @JoinTable(name = "SUBCATEGORY",
             joinColumns = {@JoinColumn(name = "CHILDID")},
             inverseJoinColumns = {@JoinColumn(name = "PARENTID")})
  private Category parent;

  @ManyToMany
  @JoinTable(name = "SUBCATEGORY",
             joinColumns = { @JoinColumn(name = "PARENTID")},
             inverseJoinColumns = { @JoinColumn(name = "CHILDID")})
  private Set<Category> subCategoryList;

@Entity
@Table(name = "SUBCATEGORY")
public class SubCategory implements Serializable {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "SUBCATEGORYID")
  private Long subCategoryId;

  @Column(name = "PARENTID")
  private Long parentId;

  @Column(name = "CHILDID")
  private Long childId;