hibernate复合主键的映射

参考资料：

1）Hibernate复合主键映射 1  http://wpmqd.blog.163.com/blog/static/7730899320121111802450/

2）Hibernate中复合主键的映射   http://sarin.iteye.com/blog/644678

3）Hibernate 复合主键http://zhangli-lisa.iteye.com/blog/476974