Hibernate: foreign keys instead of list of entites

Question

There is already a solution - how to store fk instead the whole entity on many-to-one unidirectional:

@JoinColumn(name = "message_key")
@ManyToOne(targetEntity = Messages.class, fetch = FetchType.LAZY)
private Messages message;

@Column(name = "message_key", insertable = false, updatable = false)
private Long message_fk;

Two questions:

1. How to do the same for unidirectional many-to-many? Means I have a List<Message> messages and want to keep only List<Long> message_fks.
2. Will it ensure consistency if I will never use message object? I want to use only message_fk field.