今天项目组有成员使用spring声明式事务出现下面异常，这里跟大家分享学习下。

异常信息：

org.springframework.orm.hibernate3.HibernateSystemException: identifier of an instance of com.xxx.entity.Activity was altered from 33 to null; nested exception is org.hibernate.HibernateException: identifier of an instance of com.xxx.entity.Activity was altered from 33 to null

出现异常代码：（都是在service层中的一个方法里）

@Service

@Transactional

public class GroupServiceImpl extends CoreManagerImpl<Group> implements GroupService

省略

@Override

	public Group updateGroup(Group group,Group old) throws Exception {

		Group doGroupUpdate = doGroupUpdate(group, old);

		List<SubGroup> subs = doSubGroupsUpdate(group.getSubGroups(), doGroupUpdate.getId());

		doGroupUpdate.setSubGroups(subs);

		Activity activity = updateActivity(doGroupUpdate);

		activity.setId(null);//发生异常的原因

		updateSeller(doGroupUpdate);

		doGroupUpdate.setActivity(activity);

		return doGroupUpdate;

	}

修复后代码：

	@Override

	public Group updateGroup(Group group,Group old) throws Exception {

		Group doGroupUpdate = doGroupUpdate(group, old);

		List<SubGroup> subs = doSubGroupsUpdate(group.getSubGroups(), doGroupUpdate.getId());

		doGroupUpdate.setSubGroups(subs);

		Activity activity = updateActivity(doGroupUpdate);

		//activity.setId(null);

		updateSeller(doGroupUpdate);

		doGroupUpdate.setActivity(activity);

		return doGroupUpdate;

	}

原因分析：

使用spring声明试事务，在整个事务（里面有多个子事务）没有提交成功，就将id主键设置成了null（主键不可以为null），所以会抛出上述异常。spring声明式事务是在所有子操作都完成一起提交事务的。