Real World Example for Google Cloud Spanner - JPA - Hibernate

@MappedSuperclass
@Cacheable(value = true)
@BatchSize(size = 20)
public abstract class FriggEntity implements Serializable
{
	private static final long serialVersionUID = 1L;

	private static final NoArgGenerator GENERATOR = Generators.randomBasedGenerator();

	/**
	 * ID is generated from the UUID
	 */
	@Id
	@FriggDomainDescriptor(excludedFromDataPanel = true)
	private Long id;

	@Column(nullable = false, unique = true, length = 20)
	@FriggDomainDescriptor(excludedFromDataPanel = true)
	private UUID uuid;

	@FriggDomainDescriptor(defaultVisibleInDataPanel = false, defaultVisibleInAutoForm = false)
	@Column(nullable = false)
	private Date created;

	@FriggDomainDescriptor(defaultVisibleInDataPanel = false, defaultVisibleInAutoForm = false)
	@Column(nullable = false)
	private Date updated;

	protected FriggEntity()
	{
	}

	public UUID getUuid()
	{
		if (uuid == null)
			uuid = GENERATOR.generate();
		return uuid;
	}

	public void setUuid(UUID uuid)
	{
		this.uuid = uuid;
	}

	@PrePersist
	protected void onCreate()
	{
		created = new Date();
		updated = new Date();
		if (uuid == null)
			uuid = GENERATOR.generate();
		if (id == null)
			id = uuid.getMostSignificantBits() ^ uuid.getLeastSignificantBits();
	}

	@PreUpdate
	protected void onUpdate()
	{
		updated = new Date();
	}

	@Override
	public boolean equals(Object other)
	{
		if (this == other)
			return true;
		if (!(other instanceof FriggEntity))
			return false;

		return ((FriggEntity) other).getUuid().equals(this.getUuid());
	}

	@Override
	public int hashCode()
	{
		return getUuid().hashCode();
	}

	@Override
	public boolean isSaved()
	{
		return getId() != null;
	}

}

@Entity
@Table(indexes = { @Index(unique = true, columnList = "username") })
public class Account extends FriggEntity
{
	private static final long serialVersionUID = 1L;

	@Column(length = 30, nullable = false)
	private String username;

	@FriggDomainDescriptor(header = "Password", description = "Password", passwordField = true)
	@Transient
	private String password;

	@FriggDomainDescriptor(excludedFromDataPanel = true, defaultVisibleInAutoForm = false)
	@Column(length = 200, nullable = true)
	private String passwordHash;

	@FriggDomainDescriptor(excludedFromDataPanel = true, defaultVisibleInAutoForm = false)
	@Column(length = 200, nullable = true)
	private String salt;

	@Column(length = 30, nullable = true)
	private String activeDirectoryDomain;

	@OneToMany(fetch = FetchType.LAZY, mappedBy = "account")
	private List<RoleAccount> roles = new ArrayList<RoleAccount>();

	public Account()
	{
	}

}

@Entity
@Table(indexes = { @Index(name = "IDX_ROLEACCOUNT_ACCOUNT", columnList = "account"),
		@Index(name = "IDX_ROLEACCOUNT_ROLE", columnList = "role") })
public class RoleAccount extends FriggEntity
{
	private static final long serialVersionUID = 1L;

	@FriggDomainDescriptor(defaultEditableInAutoForm = false)
	@ManyToOne(fetch = FetchType.EAGER)
	@JoinColumn(name = "account", nullable = false)
	private Account account;

	@ManyToOne(fetch = FetchType.EAGER)
	@JoinColumn(name = "role", nullable = false)
	private Role role;

	public RoleAccount()
	{
	}

	public RoleAccount(Account account, Role role)
	{
		setAccount(account);
		setRole(role);
	}

}