我有一个包含多个实体的数据库，特别是Book和User，它们之间存在如下ManyToMany关系：
书：

@Entity
@Table(name = "Books")
public class Book implements Serializable
{
  private static final long serialVersionUID = 1L;

  @Id
  @GeneratedValue(strategy = GenerationType.TABLE)
  @Column(name = "bookId", nullable = false, unique = true)
  private Long id;

  @Column(name = "title", nullable = false)
  private String title;

  @Column(name = "price", nullable = false)
  private int price;

  @ManyToMany(fetch = FetchType.EAGER)
  @JoinTable(name = "User_Book",
             joinColumns = @JoinColumn(name = "bookId"),
             inverseJoinColumns = @JoinColumn(name = "userId"))
  private Set<UserAccount> users;

用户：

@Entity
@Table(name = "UserAccounts")
public class UserAccount implements Serializable
{
  private static final long serialVersionUID = 1L;

  @Id
  @GeneratedValue(strategy = GenerationType.TABLE)
  @Column(name = "userId", nullable = false, unique = true)
  private Long id;

  @Column(name = "username", nullable = false, unique = true)
  private String username;

  @Column(name = "password", nullable = false)
  private String password;

  @ManyToMany(fetch = FetchType.EAGER)
  @JoinTable(name = "User_Book",
             joinColumns = @JoinColumn(name = "userId"),
             inverseJoinColumns = @JoinColumn(name = "bookId"))
  Set<Book> purchasedBooks;

一切正常，数据库中确实创建了表User_Book，问题似乎与该表的访问有关。
例如，

Query query = entityManager.createQuery("SELECT u FROM User_Book u");

一直在告诉我
The abstract schema type 'User_Book' is unknown
那么，我应该从头开始创建User_Book实体吗？它会像现在一样自动填充吗？也就是说，每当用户购买一本书时，该购买会记录在表中吗？