ids for this class must be manually assigned before calling save():***错误说明
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近日研究JSP中使用Hibernate出现了 ids for this class must be manually assigned before calling save():***错误，分析及解决如下：
你要操作的数据表中的id（即主键）的类型设置成了“自动增长类型”，而在hibernate.cfg.xml中，id的生成方式是assigned，即
<id name="id" type="integer">
<column name="id" />
<generator class="assigned" />
</id>
这种搭配是矛盾的！
<id name="id" type="integer">
<column name="id" />
<generator class="assigned" />
</id>
这种搭配是矛盾的！
主键的assigned生成方式由程序自动生成表的主键，即在你的测试程序中要调用setId()方法，且必
须在调用save()前调用（或者说在调用save()前必须指定id，其实就是说，主键值不能为空！）。
把主键的生成方式改为increment，它的特征是能够根据底层数据库自动选择主键生成方式。
把主键的生成方式改为increment，它的特征是能够根据底层数据库自动选择主键生成方式。
至此问题完全解决了。
- ids for this class must be manually assigned before calling save():***错误说明
- ids for this class must be manually assigned before calling save():***错误说明
- error:ids for this class must be manually assigned before calling save():
- error:ids for this class must be manually assigned before calling save()
- ids for this class must be manually assigned before calling save()
- error:ids for this class must be manually assigned before calling save():
- ids for this class must be manually assigned before calling save() hibernate
- org.hibernate.id.IdentifierGenerationException: ids for this class must be manually assigned before calling save():
- IdentifierGenerationException: ids for this class must be manually assigned before calling save()
- ids for this class must be manually assigned before calling save()..
- HibernateSystemException--ids for this class must be manually assigned before calling save()
- error:ids for this class must be manually assigned before calling save():
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