spring-data-jpa报错

在测试多对多关联时报错：如果不是本文这个原因，请另寻他路。

ItemCategory category = new ItemCategory(2l,"cat1","1",1l,new Date(),null,null);
        ItemCategory category2 = new ItemCategory(1l,"cat1","1",1l,new Date(),null,null);
        List<ItemCategory> categories = new ArrayList<>();
        categories.add(category);
        categories.add(category2);
//        itemCategoryDao.save(category);
//        itemCategoryDao.save(category2);
        Item item = new Item("item1",1l,"item1path","itemdesc1",111l,1l,new Date(),null,categories);
        itemDao.save(item);

org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: org.ruixun.yupoo.bean.ItemCategory; nested exception is java.lang.IllegalStateException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: org.ruixun.yupoo.bean.ItemCategory

错误的翻译应该是：瞬时态对象异常（TransientObjectException），对象引用了一个没有报错的瞬时态实例（object references an unsaved transient instance）

系统让你在保存item之前，先保存itemCategory。加上我的那个注释的就行了