hibernate mapping file for increment type , String, accuracy problems

The above is my id mapping should be a problem , my table id is of type String , I wrote a registration page, click on registration page is a jump , but the data is not inserted into the database .
reported the following error , do not want to type to integer, will be very troublesome ,
Caused by: org.hibernate.id.IdentifierGenerationException: Unknown integral data type for ids: java.lang.String
at org.hibernate.id.IdentifierGeneratorHelper.getIntegralDataTypeHolder (IdentifierGeneratorHelper.java: 178)
at org.hibernate.id.IncrementGenerator.initializePreviousValueHolder (IncrementGenerator.java: 121)
at org.hibernate.id.IncrementGenerator.generate (IncrementGenerator.java: 67)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId (AbstractSaveEventListener.java: 122)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId (DefaultSaveOrUpdateEventListener.java: 210)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId (DefaultSaveEventListener.java: 56)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient (DefaultSaveOrUpdateEventListener.java: 195)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate (DefaultSaveEventListener.java: 50)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate (DefaultSaveOrUpdateEventListener.java: 93)
at org.hibernate.impl.SessionImpl.fireSave (SessionImpl.java: 705)
at org.hibernate.impl.SessionImpl.save (SessionImpl.java: 693)
at org.hibernate.impl.SessionImpl.save (SessionImpl.java: 689)
at org.springframework.orm.hibernate3.HibernateTemplate $ 12.doInHibernate (HibernateTemplate.java: 685)
at org.springframework.orm.hibernate3.HibernateTemplate $ 12.doInHibernate (HibernateTemplate.java: 1)
at org.springframework.orm.hibernate3.HibernateTemplate.doExecute (HibernateTemplate.java: 405)
... 91 more
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generator can not increment the
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this last is how to solve ?