JPA如何使复合外键成为复合主键的一部分

@Embeddablepublic class EventID {    public int eventID;    public int sourceID;}@Entitypublic class Event {    @EmbeddedId    public EventID id;    @oneToMany(mappedBy="event")    public Collection<Meeting> meetings;}@Embeddablepublic class MeetingID {    public EventID eventID; // corresponds to ID type of Event    public int meetingID;}@Entitypublic class Meeting {    @EmbeddedId    public MeetingID id;    @MapsId("eventID")    @JoinColumns({        @JoinColumn(name="EventID", referencedColumnName="EventID"),        @JoinColumn(name="SourceID", referencedColumnName="SourceID")    })    @ManyToOne    public Event event;}

在JPA 2.1规范的第2.4.1节中讨论。