Hibernate映射具有空值的复合键

@Entity
public class MyClass {
    @EmbeddedId
    private MyCompositeKey key;

    // other fields and methods
}

@Embeddable
public class MyCompositeKey implements Serializable {
    @Column(name = "key_part1", nullable = true)
    private String keyPart1;

    @Column(name = "key_part2", nullable = true)
    private String keyPart2;

    // getters and setters
}