Hibernate - Anotações + Chave estrageira + Chave composta

CREATE TABLE caixas
(
  cai_numero integer NOT NULL,
  cai_cd integer,
  cai_data_envio character varying(10),
  cai_data_inicio character varying(10),
  cai_data_final character varying(10),
  CONSTRAINT pk_cai_numero PRIMARY KEY (cai_numero)
)

CREATE TABLE lotes
(
  cai_numero integer NOT NULL,
  lot_numero integer NOT NULL,
  lot_serie integer NOT NULL,
  lot_data_hora character varying(20) NOT NULL,
  CONSTRAINT pk_lotes PRIMARY KEY (lot_numero, lot_serie),
  CONSTRAINT fk_caixas FOREIGN KEY (cai_numero)
      REFERENCES caixas (cai_numero) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
)

CREATE TABLE notas
(
  not_id integer NOT NULL,
  cai_numero integer NOT NULL,
  lot_numero integer NOT NULL,
  lot_serie integer NOT NULL,
  not_sequencia integer NOT NULL,
  not_numero integer NOT NULL,
  not_valor double precision NOT NULL,
  not_cfop integer NOT NULL,
  not_data character varying(10) NOT NULL,
  not_uf_emit character varying(2) NOT NULL,
  not_ie_emit character varying(9),
  not_cnpj_emit character varying(14) NOT NULL,
  not_tipo_emit integer NOT NULL,
  not_uf_dest character varying(2) NOT NULL,
  not_ie_dest character varying(9) NOT NULL,
  not_cnpj_dest character varying(14) NOT NULL,
  not_tipo_dest integer NOT NULL,
  not_base_icms double precision NOT NULL,
  not_valor_icms double precision NOT NULL,
  not_base_icms_subst double precision NOT NULL,
  not_valor_icms_subst double precision NOT NULL,
  CONSTRAINT pk_notas PRIMARY KEY (not_sequencia),
  CONSTRAINT fk_caixas FOREIGN KEY (cai_numero)
      REFERENCES caixas (cai_numero) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT fk_lotes FOREIGN KEY (lot_numero, lot_serie)
      REFERENCES lotes (lot_numero, lot_serie) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
)

@Entity
@Table(name = "caixas")
@SuppressWarnings("serial")
public class Caixa implements Serializable {

	@Id
	@Column(name="cai_numero", nullable=false, insertable=true,	updatable=true)
	private int numero; //numero da caixa
...

@Entity
@Table(name = "lotes")
@SuppressWarnings("serial")
public class Lote implements Serializable {
	
	@ManyToOne(fetch = FetchType.LAZY)
	@JoinColumn(name="cai_numero", insertable=true, updatable=true)
	@Fetch(FetchMode.JOIN)
	//@Cascade(CascadeType.SAVE_UPDATE)
	private Caixa caixa; //caixa que o lote pertence
	
	@Id
	private LotePk lotePk;
...

@Embeddable
@SuppressWarnings("serial")
public class LotePk implements Serializable {

	@Column(name = "lot_numero")	
	private int numero;

	@Column(name = "lot_serie")
	private int serie;
...

@Entity
@Table(name = "notas")
@SuppressWarnings("serial")
public class Nota implements Serializable {
	
	@GeneratedValue(strategy = GenerationType.SEQUENCE)
	@Column(name = "not_id")
	private int id; //identificador unico da nota no banco
	
	@ManyToOne(fetch = FetchType.LAZY)
	@JoinColumn(name="cai_numero", insertable=true, updatable=true)
	@Fetch(FetchMode.JOIN)
	//@Cascade(CascadeType.SAVE_UPDATE)
	private Caixa caixa; //caixa a qual pertence a nota
	
	@ManyToOne(fetch = FetchType.LAZY)
	@JoinColumns({@JoinColumn(name="lot_numero", insertable=true, updatable=true),
				@JoinColumn(name="lot_serie", insertable=true, updatable=true)})
	@Fetch(FetchMode.JOIN)
	//@Cascade(CascadeType.SAVE_UPDATE)
	private Lote lote; //lote o qual pertence a nota
	
	@Id
	@Column(name = "not_sequencia",	nullable=false,	insertable=true, updatable=true)	
	private int sequencia; //sequencia da nota dentro do lote
...