报错：org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.hp.pms.project.entity.Project
解决办法：将many-to-one的级联设为: cascade="save-update,persist"或cascade=“all”
<many-to-one name="group" column="groupid" cascade="save-update,persist"></many-to-one>
参考博文：https://blog.csdn.net/sdyy321/article/details/5984226；
https://blog.csdn.net/u012159094/article/details/26073679